Patent-Eligible Subject Matter Reform: Background and Issues for Congress

Patent-Eligible Subject Matter Reform:

Background and Issues for Congress

Updated March 31, 2025

Congressional Research Service

https://crsreports.congress.gov

R45918

SUMMARY

Patent-Eligible Subject Matter Reform:

Background and Issues for Congress

R45918

March 31, 2025

Kevin J. Hickey

Legislative Attorney

The statutory definition of patent-eligible subject matter under Section 101 of the Patent Act (35

U.S.C. § 101) has remained essentially unchanged for more than two centuries. As a result, the

scope of patentable subject matter—that is, the types of inventions that may be patented—has

largely been left to the federal courts to develop through “common law”-like adjudication. In the

20th century, the U.S. Supreme Court established that three main types of discoveries are

categorically patent-ineligible when claimed as such: laws of nature, natural phenomena, and abstract ideas.

A series of Supreme Court decisions in the 2010s broadened the scope of these three judicial exceptions to patent-eligible

subject matter. Over a five-year period, the Supreme Court rejected, as ineligible, patents on a business method for hedging

price-fluctuation risk (Bilski v. Kappos, 561 U.S. 593 (2010)); a method for calibrating the dosage of a particular drug (Mayo

Collaborative Services v. Prometheus Laboratories, 566 U.S. 66 (2012)); isolated human DNA segments (Ass’n for

Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576 (2013)); and a method of mitigating settlement risk in financial

transactions using a computer (Alice Corp. Pty. v. CLS Bank International, 573 U.S. 208 (2014)). These cases established a

new two-step test, known as the Alice/Mayo framework, for determining whether a patent claims ineligible subject matter.

The first step of the Alice/Mayo test addresses whether the patent claims are “directed to” a law of nature, natural

phenomenon, or abstract idea. If not, the invention is patentable. If the claims are directed to one of the ineligible categories,

then the second step of the Alice/Mayo test asks whether the patent claims have an “inventive concept.” To have an inventive

concept, the patent claim must contain elements that transform the nature of the claim into a patent-eligible application of the

ineligible concept, so that the claim amounts, in practice, to something “significantly more” than a patent on the ineligible

concept itself. If the claimed invention lacks an inventive concept, then it is patent-ineligible.

The Supreme Court’s decisions have been widely recognized to effect a major change in the scope of patentable subject

matter, restricting the sorts of inventions that are patentable in the United States. The Alice/Mayo test has been the subject of

criticism, with some stakeholders arguing that the Alice/Mayo framework is vague and unpredictable, unduly restricts the

scope of patentable subject matter, reduces incentives to invest and innovate, and harms American industry’s

competitiveness. In particular, these stakeholders argue that the Alice/Mayo test creates uncertainty in the computer

technology and biotechnology industries as to whether innovations in medical diagnostics, personalized medicine, methods of

treatment, computer software, and artificial intelligence are patent-eligible. Such stakeholders—including academics, bar

associations, industry representatives, judges, and former U.S. Patent and Trademark Office (USPTO) officials—have called

for the Supreme Court or Congress to act to change the law of patentable subject matter.

Other stakeholders defend the legal status quo, arguing that the Alice/Mayo framework provides an important tool for

combating unmeritorious patent litigation, or that the revitalized limits on patentable subject matter have important benefits

for innovation. For example, some civil liberty and nonprofit organizations generally support the Alice/Mayo framework,

which they argue helps foster invention and innovation by preventing monopolies on basic research tools and concepts.

The past decade has seen a number of judicial, administrative, and legislative developments in patent-eligible subject matter

law and potential reforms responding to the Alice/Mayo decisions. On the judicial front, the Supreme Court has declined to

hear further cases on the topic, despite calls by prominent stakeholders and judges on the U.S. Court of Appeals for the

Federal Circuit. On the administrative front, the USPTO issued updated guidance in 2019 and 2024 to clarify and improve

predictability in how USPTO patent examiners make Section 101 determinations, and released several reports on the topic. In

Congress, several bills introduced in the 117th and 118th Congresses would have abrogated the Supreme Court’s recent

decisions on patent-eligible subject matter and otherwise reformed the statutory standards for patent-eligible subject matter.

Proposed changes to patent-eligible subject matter standards could have significant effects as to the types of technologies that

are patentable. The availability of patent rights, in turn, affects incentives to invest and innovate in particular fields, as well as

consumer costs and public access to technological innovation. Understanding the legal background and context of this

complex issue may aid Congress as it debates the legal and practical effects that legislative Section 101 reforms would have

if enacted.

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Patent-Eligible Subject Matter Reform: Background and Issues for Congress

Contents

Patent Law Background .................................................................................................................. 4

Requirements for Patentability .................................................................................................. 5

Section 101: Utility ............................................................................................................. 5

Section 102: Novelty........................................................................................................... 5

Section 103: Nonobviousness ............................................................................................. 6

Section 112(a): Written Description, Enablement, Best Mode ........................................... 6

Patent Claims ............................................................................................................................ 7

Section 112(b): Definiteness ............................................................................................... 7

Section 112(f): Functional Claiming ................................................................................... 7

Rights of Patent Holders ........................................................................................................... 8

Defending Against Patent Suits ................................................................................................. 9

The Law of Section 101 .................................................................................................................11

Historical Development of the Judicial Exceptions to Patent-Eligible Subject Matter ........... 12

Nineteenth Century ........................................................................................................... 12

Twentieth Century ............................................................................................................. 14

The Modern Alice/Mayo Framework ...................................................................................... 16

The Debate Over Alice/Mayo and Section 101 Reform ................................................................ 20

Criticisms of the Alice/Mayo Framework ............................................................................... 20

Defenses of the Alice/Mayo Framework ................................................................................. 23

Views on the Purposes of Section 101 .................................................................................... 24

Potential Options for Section 101 Reform .............................................................................. 26

Continued Common Law Judicial Development .............................................................. 26

Specific Statutory List of Included or Excluded Subject Matter Categories .................... 27

Replace Judicial Exceptions with a Different Standard .................................................... 28

Eliminate Implied Patentable Subject Matter Limits ........................................................ 29

Post-Alice Developments in Patent-Eligible Subject Matter Law and Proposed Reforms............ 30

Judicial Developments ............................................................................................................ 30

Administrative Developments in the USPTO ......................................................................... 31

The 2019 Revised Patent Subject Matter Eligibility Guidance ........................................ 31

2022 USPTO Report on Stakeholder Views ..................................................................... 34

2024 Artificial Intelligence Eligibility Guidance .............................................................. 34

Legislative Developments ....................................................................................................... 36

The 116th Congress .......................................................................................................... 36

The 117th Congress .......................................................................................................... 40

The 118th Congress .......................................................................................................... 42

Conclusion ..................................................................................................................................... 43

Tables

Table 1. Major Supreme Court Decisions on Patentable Subject Matter ...................................... 18

Contacts

Author Information........................................................................................................................ 43

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T

he statutory language governing patent-eligible subject matter—that is, the types of

inventions that may be patented—has remained remarkably constant over the nearly 250year history of U.S. patent law.1 Under the Patent Act of 1793, which Thomas Jefferson

authored,2 “any new and useful art, machine, manufacture or composition of matter, or any new

and useful improvement [of the same]” was patentable.3 Current law—Section 101 of the Patent

Act of 1952—permits the patenting of “any new and useful process, machine, manufacture, or

composition of matter, or any new and useful improvement thereof.”4 Through these four

expansive statutory categories,5 Congress sought to ensure that nearly “anything under the sun

made by man” is patentable6 if it meets all the requirements for patentability, such as novelty,

enablement, and nonobviousness.7

Consistent with its broad statutory language, Section 101 permits patenting in fields of applied

technology such as pharmaceuticals, biotechnology, chemistry, computer hardware and software,

electrical engineering, agriculture, mechanical engineering, and manufacturing processes.8 Even

so, the Supreme Court has long read Section 101 as categorically prohibiting patents on three

types of discoveries: “laws of nature, natural phenomena, and abstract ideas.”9 Even if “not

required by the statutory text” of Section 101, the Court has held that these three judicial

1 See generally Diamond v. Chakrabarty, 447 U.S. 303, 308–09 (1980) (tracing the history of statutory language on

patentable subject matter). This observation—and this report more generally—is limited to traditional utility patents on

useful inventions and discoveries. See 35 U.S.C. §§ 100–135. Congress did not provide patent protection for “original

and ornamental designs for an article of manufacture” (design patents), id. §§ 171–173, and for “distinct and new

variet[ies] of plants” (plant patents), id. §§ 161–164, until 1842 and 1930, respectively. See An Act in addition to an act

to promote the progress of the useful arts, and to repeal all acts and parts of acts heretofore made for that purpose, Pub.

L. No. 27-263, 5 Stat. 543 (1842); An Act to provide for plant patents, Pub. L. No. 71-245, 46 Stat. 376 (1930).

2 Graham v. John Deere Co. of Kan. City, 383 U.S. 1, 7 (1966) (describing Jefferson as “the author of the 1793 Patent

Act”).

3 An Act to promote the progress of useful Arts; and to repeal the act heretofore made for that purpose, Pub. L. No. 211, § 1, 1 Stat. 318, 319 (1793). The first Patent Act, enacted in 1790, had phrased things slightly differently: “any

useful art, manufacture, engine, machine, or device, or any improvement therein.” See An Act to promote the progress

of useful Arts, Pub. L. No. 1-7, § 1, 1 Stat. 109, 110 (1790). The Patent Acts of 1836 and 1870 used nearly identical

language as the 1793 Patent Act. See An Act to promote the progress of useful arts, and to repeal all acts and parts of

acts heretofore made for that purpose, Pub. L. No. 24-357, § 6, 5 Stat. 117, 119 (1836); An Act to revise, consolidate,

and amend the Statutes relating to Patents and Copyrights, Pub. L. No. 41-230, § 24, 16 Stat. 198, 201 (1870). In 1952,

Congress replaced the term “art,” historically used to mean a process or method, with the more modern term “process,”

while defining “process” to mean “process, art, or method.” Patent Act of 1952, Pub. L. No. 82-593, §§ 100–101, 66

Stat. 792, 797; see also 1 CHISUM ON PATENTS, Overview: Historical Development of Patent Law, § 2 n.4 (2019) (“[As

used in the 1793 Patent Act, t]he term ‘art’ meant process or method.”); Bilski v. Kappos, 561 U.S. 593, 639 (2010)

(Stevens, J., concurring) (“That change [from ‘art’ to ‘process’] was made for clarity and did not alter the scope of a

patentable ‘process.’” (citing Diamond v. Diehr, 450 U.S. 175, 184 (1981))); The Telephone Cases, 126 U.S. 1, 532

(1888) (“this art—or, what is the same thing under the patent law, this process . . .”).

4 35 U.S.C. § 101.

5 Chakrabarty, 447 U.S. at 308 (“In choosing such expansive terms as ‘manufacture’ and ‘composition of matter,’

modified by the comprehensive ‘any,’ Congress plainly contemplated that the patent laws would be given wide

scope.”).

6 Id. at 309 (quoting S. Rep. No. 1979, 82d Cong., 2d Sess., 5 (1952); H. R. Rep. No. 1923, 82d Cong., 2d Sess., 6

(1952)).

7 See 35 U.S.C. §§ 102–103, 112; see generally infra “Requirements for Patentability.”

8 See Patent Technology Centers Management, U.S. PAT. & TRADEMARK OFF., https://www.uspto.gov/patent/contactpatents/patent-technology-centers-management (last visited Mar. 6, 2025) (listing technological divisions for USPTO

examiners).

9 Diehr, 450 U.S. at 185.

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exceptions “define[] the reach of the statute as a matter of statutory stare decisis going back 150

years.”10

In a series of decisions in the 2010s, the Supreme Court relied on Section 101 to reject patent

claims on

•

•

•

•

a method for hedging price-fluctuation risks in commodity markets;11

a method for measuring metabolites in human blood to calibrate the dosage of

particular drug;12

isolated human DNA segments;13 and

a method of mitigating settlement risk in financial transactions using a

computer.14

These cases established a two-step test for patentable subject matter sometimes called the

“Alice/Mayo test” or the “Alice/Mayo framework.”15 The Court’s decisions have been widely

recognized to effect a major change in the scope of patentable subject matter, restricting the sorts

of inventions that are patentable in the United States.16 The Alice/Mayo framework has thus

shifted, for better or worse, the balance between encouraging innovation and the social costs of

exclusive rights that is at the heart of patent law.17 The effects of this change have been

particularly pronounced for computer technologies and biomedical technologies.18

As a result, there is a significant and ongoing debate about the Alice/Mayo framework, with a

number of patent law stakeholders questioning the Court’s patentable subject matter rulings.19

Critics argue that the Alice/Mayo framework is vague, unpredictable, and not administrable;20

10 Bilski v. Kappos, 561 U.S. 593, 602 (2010) (citing Le Roy v. Tatham, 55 U.S. (14 How.) 156, 174–75 (1853)).

11 Id. at 611–12.

12 Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 77–80 (2012).

13 Ass’n for Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576, 590–94 (2013).

14 Alice Corp. Pty. v. CLS Bank Int’l, 573 U.S. 208, 218–26 (2014).

15 See, e.g., Aatrix Software, Inc. v. Green Shades Software, Inc., 882 F.3d 1121, 1126, 1128 (Fed. Cir. 2018) (referring

to the inquiry as the “Alice/Mayo test” or the “Alice/Mayo analysis”). The Supreme Court refers to the two-step process

first set forth in Mayo as a “framework.” Alice, 573 U.S. at 217.

16 See U.S. PATENT & TRADEMARK OFF., PATENT ELIGIBLE SUBJECT MATTER: REPORT ON VIEWS AND

RECOMMENDATIONS FROM THE PUBLIC 23 (2017), https://www.uspto.gov/sites/default/files/documents/101Report_FINAL.pdf [hereinafter USPTO PSM REPORT] (“In general, commentators agreed that the Court decisions in

Bilski, Mayo, Myriad, and Alice have had a significant impact on the scope of patent eligible subject matter.”); Jeffrey

A. Lefstin et al., Final Report of the Berkeley Center for Law & Technology Section 101 Workshop: Addressing Patent

Eligibility Challenges, 33 BERKELEY TECH. L.J. 551, 555–59 (2018) [hereinafter BCLT Report] (describing these

Supreme Court opinions as a “sea-change”).

17 See Bonito Boats, Inc. v. Thunder Craft Boats, Inc., 489 U.S. 141, 146 (1989) (“From their inception, the federal

patent laws have embodied a careful balance between the need to promote innovation and the recognition that imitation

and refinement through imitation are both necessary to invention itself and the very lifeblood of a competitive

economy.”); Mark A. Lemley, Property, Intellectual Property, and Free Riding, 83 TEX. L. REV. 1031, 1031 (2005)

(“[Traditionally,] the proper goal of intellectual property law is to give as little protection as possible consistent with

encouraging innovation.”).

18 See USPTO PSM REPORT, supra note 16, at 34–35 (finding “a general consensus that two industries have been most

directly affected by the recent Supreme Court jurisprudence: life sciences and computer-related technologies”).

19 See generally id. at 27–34 (summarizing public comments that the Alice/Mayo framework is legally flawed, overly

broad, unpredictable, and harmful to innovation).

20 Id. at 29–30 (describing public views that the Supreme Court “has failed to articulate objective, predictable criteria”

for patentable subject matter); Hon. Paul R. Michel, The Supreme Court Saps Patent Certainty, 82 GEO. WASH. L. REV.

1751, 1758 (2014) (criticizing Court’s modern Section 101 jurisprudence as “subjective,” “indeterminate,” and “highly

(continued...)

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muddies patent law by confusing patent eligibility with distinct patent law concerns, such as

nonobviousness;21 reduces incentives to innovate and invest in particular industries, such as

biotechnology;22 or puts U.S. industry at a disadvantage with international competitors.23 Other

stakeholders defend the Alice/Mayo framework, arguing that the Court’s decisions are a part of

the ordinary common law development of Section 101;24 an important tool for combating

unmeritorious litigation25 or preventing overbroad or otherwise harmful patents;26 or beneficial to

American consumers by lowering prices.27

In response to stakeholder concerns, there have been a number of administrative and legislative

developments that seek to clarify or reform the law of Section 101. In 2019, the U.S. Patent and

Trademark Office (USPTO) issued Revised Patent Subject Matter Eligibility Guidance designed

to assist USPTO patent examiners in determining patent eligibility with greater clarity and

predictability.28 In the 116th Congress, the Senate Judiciary Committee’s Intellectual Property

Subcommittee held a series of hearings on Section 101 reform, seeking input on reform proposals

unpredictable”); David O. Taylor, Confusing Patent Eligibility, 84 TENN. L. REV. 157, 158–60 (2016) (arguing that the

Supreme Court’s Section 101 jurisprudence has created a “crisis of confusion” in patent law and that the doctrine

“lacks administrability”).

21 See USPTO PSM REPORT, supra note 16, at 31–32; Michael Risch, Everything Is Patentable, 75 TENN. L. REV. 591,

598–606 (2008) (arguing that patentability criteria such as obviousness, novelty, utility, inventorship, written

description, and enablement motivate the Supreme Court’s patentable subject matter decisions). But see Mark A.

Lemley et al., Life After Bilski, 63 STAN. L. REV. 1315, 1319–32 (2011) (arguing that the preemption/overbreadth

concerns driving Section 101 are distinct from disclosure and definiteness concerns under Section 112).

22 See, e.g., USPTO PSM REPORT, supra note 16, at 32–33, 35–38; BCLT Report, supra note 16, at 582–84; Taylor,

supra note 20, at 240 (“[The Alice/Mayo framework] substantially reduces incentives to invest in research and

development, particularly in the biotechnology and software technology areas.”).

23 See USPTO PSM REPORT, supra note 16, at 34; Ryan Davis, Kappos Calls for Abolition of Section 101 of Patent

Act, LAW360 (Apr. 12, 2016), https://www.law360.com/articles/783604/kappos-calls-for-abolition-of-section-101-ofpatent-act (quoting former USPTO Director David Kappos as stating that international competitors “no longer have to

steal U.S. technology in [biotechnology and software], since they can now take it for free”); Robert L. Stoll, Courts Are

Making Bad Patent Law, THE HILL (July 16, 2015), https://thehill.com/blogs/pundits-blog/the-judiciary/248054-courtsare-making-bad-patent-law (“The courts’ focus on subject matter eligibility as a mechanism to deny patents for

[inventions in diagnostics and personalized medicine] will drive investment into research in these technologies to other

areas. We will lose our edge in the world . . . .”).

24 See USPTO PSM REPORT, supra note 16, at 23–24.

25 See id. at 24; BCLT Report, supra note 16, at 555 (“Many technology companies that rely on software innovation . . .

welcomed the tightening of patent eligibility standards on software claims and the opportunity to seek early dismissals

of lawsuits.”); Paul R. Gugliuzza, Quick Decisions in Patent Cases, 106 GEO. L.J. 619, 652–53 (2018) (“The

invigoration of the [patent] eligibility requirement can help courts resolve infringement disputes more quickly and

cheaply by allowing validity to be resolved on the pleadings as a matter of law.”).

26 See The State of Patent Eligibility in America: Part I: Hearing Before the S. Judiciary Comm., Subcomm. on

Intellectual Property, 116th Cong. (2019) (statement of Prof. Joshua D. Sarnoff, DePaul University College of Law), at

3–8, https://www.judiciary.senate.gov/download/sarnoff-testimony [hereinafter Sarnoff Testimony]; accord Mayo

Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 86 (2012) (“[E]ven though rewarding with patents those

who discover new laws of nature and the like might well encourage their discovery, those laws and principles,

considered generally, are the basic tools of scientific and technological work. And so there is a danger that the grant of

patents that tie up their use will inhibit future innovation . . . .” (citations omitted)); Lemley et al., supra note 21, at

1329 (arguing that Section 101’s abstract ideas doctrine is “about encouraging cumulative innovation and furthering

societal norms regarding access to knowledge”).

27 USPTO PSM REPORT, supra note 16, at 27.

28 Notice, 2019 Revised Patent Subject Matter Eligibility Guidance, 84 Fed. Reg. 50 (Jan. 7, 2019). The USPTO

subsequently issued an update to this guidance in October 2019. See U.S. PAT. & TRADEMARK OFF., October 2019

Update: Subject Matter Eligibility (Oct. 2019),

https://www.uspto.gov/sites/default/files/documents/peg_oct_2019_update.pdf.

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from various patent stakeholders.29 These efforts led to the introduction of the Patent Eligibility

Restoration Act in the 117th and 118th Congresses.30 Separately, the Restoring America’s

Leadership in Innovation Act has been introduced in recent Congresses and would have reformed

Section 101 (along with several other changes to patent law).31

This report provides the necessary background and context to understand the legal and practical

effects that these legislative reforms would have if enacted.32 First, the report reviews the basic

legal principles of the U.S. patent system. Second, it examines the historical development and

current state of patentable subject matter law. Third, it reviews several articulated rationales for

Section 101 and potential options for Section 101 reform. Finally, it examines recent judicial,

administrative, and legislative developments concerning patent-eligible subject matter, including

the proposed legislative reforms to Section 101.

This report focuses on patent-eligible subject matter reform from a legal perspective. For an

analysis of these issues as they relate to innovation policy, see CRS Report R47267, Patents and

Innovation Policy, by Emily G. Blevins (2022).

Patent Law Background

Congress’s authority to grant patents derives from the Intellectual Property (IP) Clause of the U.S.

Constitution, which grants Congress the power “[t]o promote the Progress of Science and useful

Arts, by securing for limited Times to . . . Inventors the exclusive Right to their . . .

Discoveries.”33 Patents are generally available to any person who “invents or discovers any new

and useful process, machine, manufacture, or composition of matter, or any new and useful

improvement thereof.”34

Patent rights do not arise automatically. Rather, to obtain patent protection under the Patent Act,35

an inventor must formally apply for a patent with the USPTO, beginning a process called patent

prosecution.36 During prosecution, a USPTO patent examiner evaluates the patent application to

29 See generally Sen. Chris Coons & Sen. Thom Tillis, What Coons and Tillis Learned at Patent Reform Hearings,

LAW360 (June 21, 2019), https://www.law360.com/articles/1171672/. Video of the hearings and the written testimony

are available online. See The State of Patent Eligibility in America: Part I: Hearing Before the S. Judiciary Comm.,

Subcomm. on Intellectual Property, 116th Cong. (2019), https://www.judiciary.senate.gov/meetings/the-state-of-patenteligibility-in-america-part-i; The State of Patent Eligibility in America: Part II: Hearing Before the S. Judiciary

Comm., Subcomm. on Intellectual Property, 116th Cong. (2019), https://www.judiciary.senate.gov/meetings/the-stateof-patent-eligibility-in-america-part-ii; The State of Patent Eligibility in America: Part III: Hearing Before the S.

Judiciary Comm., Subcomm. on Intellectual Property, 116th Cong. (2019),

https://www.judiciary.senate.gov/meetings/the-state-of-patent-eligibility-in-america-part-iii [hereinafter, collectively,

Patent Eligibility Hearings].

30 See Patent Eligibility Restoration Act of 2024, H.R. 9474, 118th Cong. (2024); Patent Eligibility Restoration Act of

2023, S. 2140, 118th Cong. (2023); Patent Eligibility Restoration Act of 2022, S. 4734, 117th Cong. (2022).

31 See Restoring America’s Leadership in Innovation Act of 2024, H.R. 8134, 118th Cong. § 7 (2024); Restoring

America’s Leadership in Innovation Act of 2021, H.R. 5874, 117th Cong. § 7 (2021); Restoring America’s Leadership

in Innovation Act of 2020, H.R. 7366, 116th Cong. § 7 (2020); Restoring America’s Leadership in Innovation Act of

2018, H.R. 6264, 115th Cong. § 7 (2018).

32 For a succinct overview of this topic, see CRS In Focus IF12563, Patent-Eligible Subject Matter Reform: An

Overview, by Emily G. Blevins and Kevin J. Hickey (2024).

33 U.S. CONST. art. I, § 8, cl. 8.

34 35 U.S.C. § 101.

35 See Patent Act of 1952, Pub. L. No. 82-593, 66 Stat. 792 (codified as amended at 35 U.S.C. §§ 1–390).

36 See Applying for Patents, U.S. PAT. & TRADEMARK OFF., https://www.uspto.gov/patents/basics/apply (last visited

Mar. 6, 2025).

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ensure that it meets all the applicable legal requirements to merit the grant of a patent.37 To be

patentable, an invention must be (1) directed at patent-eligible subject matter, (2) useful, (3) new,

(4) nonobvious, and (5) adequately disclosed and claimed in the patent application.38 If the

USPTO finds these requirements met, it will issue (i.e., grant) the patent.39 Patents typically

expire 20 years after the initial patent application.40

The current law of patent-eligible subject matter will be discussed separately in detail below.41

The remainder of this section briefly reviews the other requirements for patentability, the scope

and effect of patent claims, and the legal rights granted to the holder of a valid patent.

Requirements for Patentability

Section 101: Utility

Along with its subject matter requirements, Section 101 contains a requirement that a patented

invention must be “useful.”42 In particular, courts have held that an invention must have both a

specific and substantial utility to be patentable.43 The utility requirement derives from the

Constitution’s command that patent laws exist to “promote the Progress of . . . useful Arts.”44 The

constitutional purpose of patent law thus requires a “benefit derived by the public from an

invention with substantial utility,” where the “specific benefit exists in currently available

form.”45 This standard for utility is low, however, requiring only that the claimed invention have

some “significant and presently available benefit to the public” that “is not so vague as to be

meaningless.”46

Section 102: Novelty

Perhaps the most fundamental requirement for patentability is that the claimed invention must be

new. The USPTO will not issue a patent if “the claimed invention was patented, described in a

printed publication, or in public use, on sale, or otherwise available to the public before the

effective filing date of the claimed invention.”47 In other words, if every element of the claimed

invention is already disclosed in the “prior art”—the information available to the public at the

time of the patent application—then the alleged inventor “has added nothing to the total stock of

knowledge,” and no valid patent may issue to her.48

37 35 U.S.C. § 131.

38 See id. §§ 101–103, 112.

39 Id. § 131.

40 Id. § 154(a)(2).

41 See infra “The Law of Section 101.”

42 35 U.S.C. § 101.

43 Brenner v. Manson, 383 U.S. 519, 534–35 (1966); In re Fisher, 421 F.3d 1365, 1371 (Fed. Cir. 2005).

44 Stiftung v. Renishaw PLC, 945 F.2d 1173, 1180 (Fed. Cir. 1991) (citing Brenner, 383 U.S. at 528–29).

45 Brenner, 383 U.S. at 534–35.

46 In re Fisher, 421 F.3d at 1371–72.

47 35 U.S.C. § 102(a)(1). There are certain exceptions to this requirement when, for example, the prior-art disclosure

derives from the inventor and the patent application is made within one year of the disclosure. Id. § 102(b)(1).

48 Great Atl. & Pac. Tea Co. v. Supermarket Equip. Corp., 340 U.S. 147, 153 (1950); Graham v. John Deere Co. of

Kan. City, 383 U.S. 1, 6 (1966) (“Congress may not authorize the issuance of patents whose effects are to remove

existent knowledge from the public domain, or to restrict free access to materials already available.”).

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Section 103: Nonobviousness

Even if a claimed invention is novel in the narrow sense that it is not “identically disclosed” in a

prior-art reference (such as an earlier patent or publication), the invention must further be

nonobvious to be patentable.49 Specifically, an invention cannot be patented if “the differences

between the claimed invention and the prior art are such that the claimed invention as a whole

would have been obvious . . . to a person having ordinary skill” in the relevant technology.50

When determining obviousness, courts also evaluate secondary considerations (also known as

“objective indicia”) of nonobviousness such as “commercial success, long felt but unsolved

needs, [or] failure of others . . . to give light to the circumstances surrounding the origin of the

subject matter sought to be patented.”51 By its nature, obviousness is an “expansive and flexible”

inquiry that cannot be reduced to narrow, rigid tests.52 Nonetheless, if an invention merely

combines “familiar elements according to known methods,” yielding only “predictable results,” it

is likely to be obvious.53

Section 112(a): Written Description, Enablement, Best Mode

Finally, the Patent Act imposes several requirements relating to the technical disclosures in the

patent application. These provisions are intended to ensure that the patent adequately describes

the invention such that the public can use the invention after the expiration of the patent term. 54

Section 112(a) of the Patent Act requires that patents must contain a “specification” that includes

a written description of the invention, and of the manner and process of making and using

it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to

. . . make and use the same, and shall set forth the best mode contemplated by

the inventor or joint inventor of carrying out the invention.55

This statutory language yields three basic disclosure requirements for patentability.56 First, to

satisfy the written description requirement, the specification must “reasonably convey[] to those

skilled in the art that the inventor had possession of the claimed subject matter as of the filing

date” of the patent application.57 Second, to satisfy the enablement requirement, the specification

must contain enough information to teach a person skilled in the art how “to make and use the

invention without undue experimentation.”58 Finally, to satisfy the best mode requirement, if the

inventor knew of a preferred way of practicing her invention at the time of the patent application,

the specification must disclose that “preferred embodiment[]” of the invention.59

49 35 U.S.C. § 103.

50 Id. Patent law often relies on the concept of a “person having ordinary skill in the art,” a “hypothetical person” with a

typical level of skill in the relevant technology who is “presumed to be aware of all the pertinent prior art” in the

particular field. See Standard Oil Co. v. Am. Cyanamid Co., 774 F.2d 448, 454 (Fed. Cir. 1985).

51 Graham, 383 U.S. at 17–18; see also Apple Inc. v. Samsung Elecs. Co., 839 F.3d 1034, 1048 (Fed. Cir. 2016) (en

banc) (“Objective indicia of nonobviousness must be considered in every case where present.).

52 KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 415–19 (2007).

53 Id. at 416.

54 See Kewanee Oil Co. v. Bicron Corp., 416 U.S. 470, 480–81 (1974).

55 35 U.S.C. § 112(a) (emphases added).

56 See Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 736 (2002); Ariad Pharms., Inc. v. Eli

Lilly & Co., 598 F.3d 1336, 1344 (Fed. Cir. 2010) (en banc).

57 Ariad, 598 F.3d at 1351.

58 In re Wands, 858 F.2d 731, 735 (Fed. Cir. 1988).

59 Eli Lilly & Co. v. Barr Labs., Inc., 251 F.3d 955, 963 (Fed. Cir. 2001). Failure to disclose the best mode is not a basis

on which a patent claim can be invalidated in subsequent patent infringement proceedings. 35 U.S.C. § 282(b)(3)(A).

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Patent Claims

Section 112(b): Definiteness

If granted, the legal scope of the patent is defined by the patent claims, a sequence of statements

that formally set forth the patentee’s asserted rights. In essence, while the specification explains

the invention in a technical sense, the claims set forth the legal effect of the patent.60 Much as a

deed may describe the boundaries of a tract of land, the claims define the “metes and bounds” of

the patent right.61 Patent claims must be sufficiently definite to be valid—that is, they must

“particularly point[] out and distinctly claim[] the subject matter which the inventor . . . regards as

the invention.”62 In other words, when the claims are read in context, they must “inform, with

reasonable certainty, those skilled in the art about the scope of the invention.”63

Section 112(f): Functional Claiming

For the most part, the current Patent Act uses a system of peripheral claiming, in which the patent

claims formally set out the outer boundaries of the patentee’s rights.64 However, the Patent Act

still retains elements of its former system of central claiming, in which the patentee would

describe the core principles or examples of what he had invented, but need not formally delineate

the outer boundaries of his rights.65 For example, under the doctrine of equivalents, an accused

infringer may be found liable even if his product does not literally meet every element of the

patent claims, if the differences between a claim element and its alleged equivalent in the accused

product are “insubstantial.”66

60 See Ariad, 598 F.3d at 1347 (Fed. Cir. 2010); In re Vamco Mach. & Tool, Inc., 752 F.2d 1564, 1577 n.5 (Fed. Cir.

1985).

61 Corning Glass Works v. Sumitomo Elec. U.S.A., Inc., 868 F.2d 1251, 1257 (Fed. Cir. 1989).

62 35 U.S.C. § 112(b); Laitram Corp. v. NEC Corp., 163 F.3d 1342, 1347 (Fed. Cir. 1998) (“[I]t is the claims, not the

written description, which define the scope of the patent right.”).

63 Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898, 901 (2014).

64 See 35 U.S.C. § 112(b); Mark A. Lemley, Software Patents and the Return of Functional Claiming, 2013 WIS. L.

REV. 905, 911 (2013) (“Today, peripheral claiming is universal [in patent law]; patentees write claims in an effort to

define the outer boundaries of their invention.”); Jeanne C. Fromer, Claiming Intellectual Property, 76 U. CHI. L. REV.

719, 725–30 (2009) (explaining the distinction between peripheral and central claiming systems for intellectual

property). Until the late 19th century, however, central claiming prevailed: the patentee had only to describe the core

principle or an example of his invention, and courts would decide whether the accused infringer’s product or method

was sufficiently similar to the patentee’s invention to infringe the patent. See Lemley, supra, at 910–11; Fromer, supra,

at 731–33. Peripheral claiming began as a defensive strategy by patentees to describe their invention at a higher level of

generality, and the gradual switch toward the modern patent claiming was eventually codified in the Patent Act in 1870.

See An Act to revise, consolidate, and amend the Statutes relating to Patents and Copyrights, Pub. L. No. 41-230 § 26,

16 Stat. 198, 201 (1870) (requiring patent applicant to “particularly point out and distinctly claim the part,

improvement, or combination which he claims as his invention or discovery”); see generally Fromer, supra, at 731–35

(reviewing American patent law’s historical shift from central to peripheral claiming); Dan L. Burk & Mark A. Lemley,

Fence Posts or Sign Posts? Rethinking Patent Claim Construction, 157 U. PA. L. REV. 1743, 1766–71 (2009) (same).

This account of patent-claiming history is somewhat simplified: notably, despite the 1870 statutory shift, the Patent Act

retained (and retains) features of central claiming. See Burk & Lemley, supra, at 1771 (“[I]t may be fairer to say that

during the twentieth century we had not a peripheral-claiming system, but a hybrid peripheral claiming system.”).

65 See Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17, 27 n.4 (1997) (“[T]he abandonment of

‘central’ claiming [in American patent law] may be overstated.”); Fromer, supra note 64, at 735–41 (describing

“vestiges” of central claiming in the modern Patent Act).

66 See Warner-Jenkinson, 520 U.S. at 39–40; Graver Tank & Mfg. Co. v. Linde Co., 339 U.S. 605, 608–09 (1950)

(laying out factors to consider in determining equivalence).

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A potential danger of a peripheral claiming system is that patentees may seek to claim more than

they invented by couching the patent claims in broad, functional language—that is, by claiming a

result or goal without limitation to any specific structure or device that accomplishes the result.67

In Halliburton Oil Well Cementing Co. v. Walker, the Supreme Court limited this practice,

invalidating as indefinite a “functional” patent claim, in which the invention—an apparatus for

determining the location of an obstruction in an oil well—was claimed not in terms of specific

machinery, but instead as a “means for” performing various functions.68

Functional claims (also known as “means-plus-function” claims) such as those in Halliburton

may be convenient for the patentee, who can express a claim element in terms of a general end,

rather than an “exhaustive list” of every possible apparatus that could be used to perform that

goal.69 On the other hand, as Halliburton recognized, functional claims may be overbroad and

ambiguous, or permit the patentee to claim more than he actually invented.70 In the Patent Act of

1952, Congress enacted current Section 112(f) as a compromise for functional claims, overruling

Halliburton71 but providing a standard to make functional claims more definite.72

Under Section 112(f), a patentee may opt to express a claim element as “a means or step for

performing a specified function without the recital of structure, material, or acts in support

thereof.”73 If the patentee chooses to claim functionally, however, the claim is construed not to

cover all possible means of performing the function, but only “the corresponding structure,

material, or acts described in the specification and equivalents thereof.”74 Courts have held that a

patentee is presumed to invoke Section 112(f) when the term “means” is used in the claims.75

Conversely, there is a presumption that the patentee does not invoke Section 112(f) if she does not

use the term “means,” but that presumption may be overcome, such that Section 112(f) will apply

to any claim that fails to recite a “sufficiently definite structure” for performing a function.76

Rights of Patent Holders

With some exceptions, a patent is generally granted “for a term beginning on the date on which

the patent issues and ending 20 years from the date on which the application for the patent was

67 See Lemley, supra note 64, at 911–13. Such claiming should in theory be prohibited on novelty or enablement

grounds, see 35 U.S.C. §§ 102, 112(a), but the problem persists, for example, in modern software patents. See Lemley,

supra note 64, at 921–23 (citing examples).

68 See 329 U.S. 1, 8–9, 12–13 (1946).

69

Stephen Winslow, Means for Improving Modern Functional Patent Claiming, 98 GEO. L.J. 1891, 1892 (2010) (“A

patent can be clearer, more concise, and more comprehensible when the patentee drafts her claims using language

describing what a particular element does, rather than giving an exhaustive list of the various structures that could

provide that function within her invention.”).

70 See Halliburton, 329 U.S. at 12.

71 See Williamson v. Citrix Online, LLC, 792 F.3d 1339, 1347 (Fed. Cir. 2015) (en banc) (“In enacting [§ 112(f)],

Congress struck a balance in allowing patentees to express a claim limitation by reciting a function to be performed

rather than by reciting structure for performing that function, while placing specific constraints on how such a

limitation is to be construed . . . .”); P.J. FEDERICO, COMMENTARY ON THE NEW PATENT ACT (West 1954), reprinted in

75 J. PAT. & TRADEMARK OFF. SOC’Y 161, 186 (1993) (observing that “[t]he last paragraph of section 112” means that

“decisions such as that in [Halliburton Oil] are modified or rendered obsolete . . . .”).

72 Valmont Indus. v. Reinke Mfg. Co., 983 F.2d 1039, 1042 (Fed. Cir. 1993).

73 35 U.S.C. § 112(f).

74

Id. (emphasis added).

75 Williamson, 792 F.3d at 1348 (quoting Watts v. XL Sys., Inc., 232 F.3d 877, 880 (Fed. Cir. 2000)).

76 Id.

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filed.”77 The Patent Act includes provisions that may modify the 20-year term, including to

account for excessive delays in patent examination at the USPTO,78 or delays associated with

obtaining marketing approval from other federal agencies.79

Once granted, a valid patent gives the patent holder the exclusive right to make, use, offer to sell,

sell, or import the invention in the United States until the patent expires.80 Any other person who

practices the invention (i.e., makes, uses, offers to sell, sells, or imports it) without permission

from the patent holder infringes the patent and may be liable for monetary damages and

injunctive relief if sued by the patentee.81 To obtain relief from infringement, the patentee must

generally sue in court.82 Patent law is an area of exclusive federal jurisdiction,83 and the

traditional forum for most patent disputes is federal district court.84 Although patent suits may be

filed in any district court across the country with jurisdiction over the defendant and proper

venue,85 a single specialized court, the U.S. Court of Appeals for the Federal Circuit (Federal

Circuit), hears all appeals in patent cases.86

Defending Against Patent Suits

Parties accused of patent infringement may defend on several grounds. First, the accused

infringer may claim an “absence of liability” because of noninfringement.87 In other words, even

presuming the patent is valid, the patentee may fail to prove that the activities of the accused

infringer fall within the scope of the patent claims—that is, the accused infringer is not making,

using, selling, or importing the patented invention.88 Second, although patents benefit from a

77 35 U.S.C. § 154(a).

78 Id. § 154(b)(1).

79 Id. § 156. In the pharmaceutical context, patents claiming a drug product or medical device (or a method of using or

manufacturing the same) may be extended for up to five years to account for delays in obtaining regulatory approval, if

certain statutory conditions are met. See Eli Lilly & Co. v. Medtronic, Inc., 496 U.S. 661, 670–71 (1990); Merck & Co.

v. Hi-Tech Pharmacal Co., 482 F.3d 1317, 1320–21 (Fed. Cir. 2007); Stephanie Plamondon Bair, Adjustments,

Extensions, Disclaimers, and Continuations: When Do Patent Term Adjustments Make Sense?, 41 CAP. U. L. REV. 445,

460 (2013).

80 35 U.S.C. § 271(a).

81 Id. §§ 271, 281, 283–85.

82 35 U.S.C. § 281.

83 28 U.S.C. § 1338.

84 In 2023, roughly 3,108 patent lawsuits were filed in federal district courts, as compared to 1,192 petitions filed

before the Patent Trial and Appeal Board (PTAB). See 2023 Patent Dispute Report: Year in Review, UNIFIED PATENTS

(Jan. 8, 2024), https://www.unifiedpatents.com/insights/2024/1/8/patent-dispute-report-2023-in-review. The third main

forum for patent disputes is the International Trade Commission (ITC), which has authority to conduct administrative

trials (called “Section 337 investigations”) into whether imported goods violate patent and other intellectual property

rights. See 19 U.S.C. § 1337. The ITC usually receives fewer than 100 complaints per year (and not all of these are

patent cases). See Section 337 Statistics: Number of New, Completed, and Active Investigations by Fiscal Year

(Updated Quarterly), ITC,

https://www.usitc.gov/intellectual_property/337_statistics_number_new_completed_and_active.htm (last updated Feb.

3, 2025).

85 See generally TC Heartland LLC v. Kraft Foods Grp., 137 S. Ct. 1514, 1518–21 (2017) (addressing scope of patent

venue statute); Gunn v. Minton, 568 U.S. 251 (2013) (addressing scope of federal patent subject matter jurisdiction);

Xilinx, Inc. v. Papst Licensing GmbH & Co. KG, 848 F.3d 1346 (Fed. Cir. 2017) (addressing personal jurisdiction in

patent dispute).

86 28 U.S.C. § 1295(a)(1).

87 35 U.S.C. § 282(b)(1).

88 To prove direct infringement, the plaintiff must show that each element contained in a patent claim is practiced by

(continued...)

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presumption of validity, the accused infringer may assert that the patent is invalid.89 To prove

invalidity, the accused infringer must show, by clear and convincing evidence, that the USPTO

should not have granted the patent because it failed to meet the requirements for patentability.90

Thus, for example, the accused infringer may argue that the invention lacks novelty, is obvious, or

claims nonpatentable subject matter; that the patent fails to enable the invention; or that the patent

claims are indefinite.91 Finally, the accused infringer may assert as a defense that the patent is

unenforceable based on the inequitable or illegal activities of the patent holder, such as obtaining

the patent through fraud on the USPTO.92 While the patent holders bears the burden of proving

infringement,93 the accused infringer bears the burden of proving invalidity or inequitable

conduct.94

Following the passage of the 2011 Leahy-Smith America Invents Act (AIA),95 the Patent Trial

and Appeal Board (PTAB) has become an increasingly important forum for patent disputes.96 The

AIA created several new administrative procedures for challenging patent validity, including (1)

post-grant review (PGR), which allows any person to challenge patent validity based on any of

the requirements of patentability if the PGR petition is filed within nine months of the patent’s

issuance;97 (2) inter partes review (IPR), which allows any person other than the patentee to

challenge patent validity on limited grounds (novelty or obviousness based on prior patents or

printed publications) at any time more than nine months following the patent’s issuance;98 and (3)

a transitional program for covered business method patents (CBM), a PGR-like process limited to

certain patents claiming “business methods” that was available only through September 2020.99

Of these procedures, IPR is by far the most widely used.100 IPRs can only be used to seek

cancellation of patents based on a lack of novelty or nonobviousness, and not on Section 101

grounds (i.e., claiming ineligible subject matter).101

the alleged infringer, either literally or by an equivalent. Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S.

17, 29–30 (1997). Often, whether or not the accused infringer’s activities fall within the patent claims depends upon

claim construction: how the words used in the patent claims are interpreted. See generally Markman v. Westview

Instruments, Inc., 517 U.S. 370, 372–74 (1996); Phillips v. AWH Corp., 415 F.3d 1303, 1312–19 (Fed. Cir. 2005) (en

banc).

89 35 U.S.C. § 282(a), (b)(2)–(3).

90 Id. § 282(b)(2)–(3); Microsoft Corp. v. i4i Ltd. P’ship, 564 U.S. 91, 95–96 (2011).

91 See supra “Requirements for Patentability.”

92 35 U.S.C. § 282(b)(1); Therasense, Inc. v. Becton, Dickinson & Co., 649 F.3d 1276, 1285, 1290–91 (Fed. Cir. 2011)

(en banc).

93 Medtronic, Inc. v. Mirowski Fam. Ventures, LLC, 571 U.S. 191, 193 (2014).

94 35 U.S.C. § 282(a); Therasense, 649 F.3d at 1291.

95 Pub. L. No. 112-29, 125 Stat. 284 (2011).

96 See generally CRS Report R48016, The Patent Trial and Appeal Board and Inter Partes Review, by Christopher T.

Zirpoli and Kevin J. Hickey (2024); Rochelle Cooper Dreyfuss, Giving the Federal Circuit a Run for Its Money:

Challenging Patents in the PTAB, 91 NOTRE DAME L. REV. 235, 249 (2015).

97 35 U.S.C. §§ 321–329.

98 Id. §§ 311–319.

99 Pub. L. No. 112-29, § 18, 125 Stat 284, 329–30 (2011) (not codified in U.S.C.).

100 See PTAB Trial Statistics: FY23 End of Year Outcome Roundup, USPTO,

https://www.uspto.gov/sites/default/files/documents/ptab_aia_fy2023__roundup.pdf (last visited Mar. 6, 2025), at 3

(98% of petitions filed with PTAB in FY2023 were IPRs).

101 35 U.S.C. § 311(b).

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The Law of Section 101

At a general level, there are two basic requirements for an invention to claim patent-eligible

subject matter. First, the invention must fit into one or more of the four statutory categories in

Section 101—the claimed invention must be a (1) process, (2) machine, (3) manufacture, or (4)

composition of matter.102 Given the (intentionally) expansive nature of these terms, nearly all

claimed inventions will satisfy this requirement.103 Still, exceptions to this rule do exist. For

example, in In re Nuijten, the Federal Circuit held that a transitory electromagnetic signal was

neither a process, machine, manufacture, or composition of matter, and was therefore not patenteligible subject matter.104

Because most claimed inventions fit into one of the four statutory categories, the second

requirement tends to be more practically important, and receives more attention.105 The second

patentable subject matter requirement is that the invention cannot claim one of the judicially

created categories of ineligible subject matter. That is, the claimed invention must not be a (1) law

of nature, (2) natural phenomenon, or (3) abstract idea.106 As explained below, the modern

Supreme Court has articulated a two-step test for this second requirement, known as the

Alice/Mayo framework.107

The Supreme Court has justified the three ineligible categories as necessary to prevent patent

monopolies on the “‘basic tools of scientific and technological work,’” which “might tend to

impede innovation more than it would tend to promote it.”108 Thus, the Court has explained that

“a new mineral discovered in the earth or a new plant found in the wild is not patentable subject

matter. Likewise, Einstein could not patent his celebrated law that E=mc2; nor could Newton have

102 35 U.S.C. § 101.

103 See Lemley et al., supra note 21, at 1328 (“[P]atent claims almost never fall outside of the four fundamental

categories of § 101 . . . .”).

104 500 F.3d 1346, 1354–57 (Fed. Cir. 2007).

105 See Kevin Emerson Collins, Patent-Ineligibility As Counteraction, 94 WASH. U. L. REV. 955, 968 (2017)

(“Contemporary debates over patent-ineligibility rarely parse the plain meanings of [the four statutory categories].

They focus instead on a set of judicial exclusions from patent-eligibility that are not expressly codified in the statute:

laws of nature, products of nature, and abstract ideas . . . .”).

106 Diamond v. Diehr, 450 U.S. 175, 185 (1981). Diehr’s modern distillation of patentable subject matter doctrine to

these three categories is a somewhat simplified version of the doctrine’s historical development, which often identified

patent-ineligible categories in addition to these three. See, e.g., Daniel J. Klein, The Integrity of Section 101: A ‘New

and Useful’ Test for Patentable Subject Matter, 93 J. PAT. & TRADEMARK OFF. SOC’Y 287, 288 (2011) (listing eight

terms that the Court has used to denote patent-ineligible subject matter); Michel, supra note 20, at 1757 (counting six

categories of patent-ineligible subject matter); accord Emily Michiko Morris, Intuitive Patenting, 66 S.C. L. REV. 61,

66 n.31 (2014) (describing the Supreme Court’s patentable subject matter jurisprudence as “insolubly murky”).

In addition to the three modern patent-ineligible categories and their close variants (such as “products of nature” or

“physical phenomena” as synonyms for natural phenomena, see Diamond v. Chakrabarty, 447 U.S. 303, 309, 313

(1980), or “scientific truth” as a synonym for a law of nature, see Mackay Radio & Tel. Co. v. Radio Corp. of Am., 306

U.S. 86, 94 (1939)), courts have at times referenced “principles,” “natural agencies,” “functions of a machine,” “effects

of a machine,” “mathematical formulas,” “algorithms,” “mental processes,” “mental steps,” and “printed matter” as

patent-ineligible categories. See Le Roy v. Tatham, 55 U.S. 156, 175 (1852) (“principle[s]” and “natural agencies”);

Corning v. Burden, 56 U.S. 252, 268 (1853) (“function or abstract effect of a machine”); Gottschalk v. Benson, 409

U.S. 63, 67, 72 (1972) (“mathematical formula,” “algorithm,” “mental processes”); Diamond v. Diehr, 450 U.S. 175,

195–200 (1981) (Stevens, J., dissenting) (reviewing history of “mental steps” doctrine that prohibited patents on

“processes involving mental operations”); Praxair Distribution, Inc. v. Mallinckrodt Hosp. Prod. IP Ltd., 890 F.3d

1024, 1031–33 (Fed. Cir. 2018) (“printed matter”).

107 See infra “The Modern Alice/Mayo Framework.”

108 Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 71 (2012) (quoting Gottschalk v. Benson, 409

U.S. 63, 67 (1972)).

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patented the law of gravity.”109 At the same time, the Court has said that even if a mathematical

formula or law of nature is not patentable “in the abstract,” a practical application of such a

principle or law “to a new and useful end” is patent-eligible.110

Beyond such broad illustrations, it is not easy to define what an “abstract idea,” “law of nature,”

or “natural phenomenon” is.111 Because these exceptions to patent-eligible subject matter are

judicially created, they have no formal statutory definition; their meaning has instead been

developed through two centuries of case-by-case “common law” adjudication in the federal

courts.112 As a result, the scope of patentable subject matter has waxed and waned over time,

depending on the trends in judicial decisions.113

This section overviews the leading Supreme Court cases addressing patent-eligible subject matter,

beginning with formative cases from the 19th century and culminating in the series of 2010s

Supreme Court decisions that have led some to call for legislative reform of Section 101.114

Historical Development of the Judicial Exceptions to

Patent-Eligible Subject Matter

Nineteenth Century

The 1853 case of Le Roy v. Tatham, the “fountainhead” of American patentable subject matter

jurisprudence,115 concerned a patent on machinery to manufacture metal pipes that exploited a

109 Diamond v. Chakrabarty, 447 U.S. 303, 309 (1980).

110 See, e.g., Diehr, 450 U.S. at 187; Funk Bros. Seed Co. v. Kalo Inoculant Co., 333 U.S. 127, 130 (1948); Mackay

Radio & Telegraph Co. v. Radio of Am., 306 U.S. 86, 94 (1939); Le Roy, 55 U.S. at 174–75.

111 See Morris, supra note 106, at 62 (describing the Supreme Court’s patentable subject matter jurisprudence as

“insolubly murky”); Klein, supra note 106, at 289 (describing the three categories of nonpatentable subject matter as

“metaphysically vague and extra-statutory”); Funk Bros., 333 U.S. at 134–35 (Frankfurter, J., concurring) (“It only

confuses the issue, however, to introduce such terms as ‘the work of nature’ and the ‘laws of nature.’ For these are

vague and malleable terms infected with too much ambiguity and equivocation. Everything that happens may be

deemed ‘the work of nature,’ and any patentable composite exemplifies in its properties ‘the laws of nature.’”).

112 See, e.g., Peter S. Menell, Forty Years of Wondering in the Wilderness and No Closer to the Promised Land:

Bilski’s Superficial Textualism and the Missed Opportunity to Return Patent Law to Its Technology Mooring, 63 STAN.

L. REV. 1289, 1307 (2011) (“Since the founding of our nation, courts have evolved [patentable subject matter limits]

within a hybrid constitutional/common law tradition.”); Lemley et al., supra note 21, at 1325 (describing the three

judicially created ineligible categories as “common law exceptions” to patentable subject matter).

113 The evolving standards applied to the patentability of computer software over the last 50 years are just one notable

example. See generally Lemley et al., supra note 21, at 1317–19 (reviewing the “tortured history” of the patentability

of software). Compare, e.g., Benson, 409 U.S. 63 (method for converting binary-coded decimal numerals into pure

binary numerals on computer is not patentable subject matter) with State Street Bank v. Signature Fin. Grp., 149 F.3d

1368, 1373 (Fed. Cir. 1998) (Rich, J.) (transformations of data are patentable so long as they produce “a useful,

concrete and tangible result”), abrogated by In re Bilski, 545 F.3d 943, 960 (Fed. Cir. 2008) (en banc) and Alice Corp.

Pty. v. CLS Bank Int’l, 573 U.S. 208, 224–26 (2014) (computer-implemented business method not patentable because

it is an abstract idea lacking an “inventive concept”). For a broader review of the history of patentable subject matter

jurisprudence, see, e.g., Jeffrey A. Lefstin, Inventive Application: A History, 67 FLA. L. REV. 565, 570–645 (2015);

Max Stul Oppenheimer, Patents 101: Patentable Subject Matter and Separation of Powers, 15 VAND. J. ENT. & TECH.

L. 1, 5–28 (2012); Joshua D. Sarnoff, Patent-Eligible Inventions After Bilski: History and Theory, 63 HASTINGS L.J.

53, 63–90 (2011); John F. Duffy, Rules and Standards on the Forefront of Patentability, 51 WM. & MARY L. REV. 609,

623–46 (2009).

114 See infra Table 1.

115 See, e.g., Lefstin, supra note 113, at 594 (describing Le Roy as “the fountainhead of subject-matter exclusion in

American patent law”); Menell, supra note 112, at 1296 (describing Le Roy as “the foundation for much patentable

subject matter jurisprudence”).

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newly developed property of lead.116 Although the Court ultimately did not decide the case on

subject matter grounds,117 Le Roy relied on influential English patent cases118 to set forth a basic

distinction between abstract “principles” and natural laws (which may not be patented) and

practical applications of those principles (which may be patented).119 The Court stated that “[a]

principle, in the abstract, is a fundamental truth; an original cause; a motive; these cannot be

patented, as no one can claim in either of them an exclusive right.”120 On the other hand, a “new

property discovered in matter, when practically applied, in the construction of a useful article of

commerce or manufacture, is patentable,” for the “invention is not in discovering [the natural

principles], but in applying them to useful objects.”121

In its next term, the Court applied this rule to Samuel Morse’s patent on the telegraph in the

famous case O’Reilly v. Morse.122 Although the Court found that Morse was the first inventor of

the telegraph and sustained much of his patent,123 the Court rejected Morse’s eighth claim to any

“use of the motive power of the electric or galvanic current . . . however developed for marking

or printing intelligible characters, signs, or letters, at any distances, being a new application of

that power of which I claim to be the first inventor or discoverer.”124 Observing that “the

discovery of a principle in natural philosophy or physical science, is not patentable,”125 Chief

Justice Roger Taney’s majority opinion held that Morse’s eighth claim was “too broad” because

he had not discovered “that the electric or galvanic current will always print at a distance, no

matter what may be the form of the machinery” used, but only that the specific machinery

disclosed in the patent specification would do so.126

In the second half of the 19th century, the Court issued a series of important decisions on the

patentability of processes. The result of these cases was a move away from an earlier rule that

prohibited “pure” method patents as ineligible (i.e., a process claimed independently of the

specific machinery used to accomplish the method) either by construing nominal process patents

as claiming a machine or limiting the process patents to the machinery disclosed and its

equivalents.127 In Cochrane v. Deener, which involved a patent on an improved manufacturing

process for flour, the Court defined a patentable process as “a mode of treatment of certain

materials to produce a given result. It is an act, or a series of acts, performed upon the subjectmatter to be transformed and reduced to a different state or thing.”128 Cochrane held that such

116 55 U.S. (14 How.) 156, 176–77 (1853).

117 The dispositive issue in the case was the scope of the patent claims. See infra note 181; Lefstin, supra note 113, at

595 (“The outcome in Le Roy therefore turned entirely on the Court’s narrow construction of the claim.”).

118 For a full historical account of these English cases and how they shaped the Supreme Court’s jurisprudence, see

Lefstin, supra note 113, at 577–644.

119 Le Roy, 55 U.S. at 174–75.

120 Id. at 175.

121 Id.

122 56 U.S. 62 (1853).

123 Id. at 111–12, 123–24.

124 Id. at 112–20.

125 Id. at 116.

126 Id. at 117, 119.

127 See, e.g., Corning v. Burden, 56 U.S. (15 How.) 252, 268–70 (1853) (construing “equivocal” patent to claim a

machine, and not a process, to save its validity because a “process” in the sense of “the function of a machine, or the

effect produced by it” cannot be patented); see generally Sarnoff, supra note 113, at 67 (“[A]t the end of the eighteenth

century, pure method patents—methods claiming all future applications and not merely those substantially similar to

the disclosed implementing machinery and their equivalents—were ineligible for protection and remained so until the

late nineteenth century.”) & id. n. 88 (collecting cases).

128 94 U.S. 780, 788 (1876).

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methods are patentable “irrespective of the particular form of the instrumentalities used.”129

Similarly, in Tilghman v. Proctor, the Court held that a method for separating fat into glycerin and

fatty acids using water, pressure, and heat was patentable.130

In The Telephone Cases, the Court distinguished Morse to allow Alexander Graham Bell’s patent

claim on a “method of and apparatus for transmitting vocal or other sounds telegraphically, as

herein described, by causing electrical undulations, similar in form to the vibrations of the air

accompanying the said vocal or other sounds, substantially as set forth.”131 Chief Justice Edward

Douglass White interpreted Morse as holding that “the use of magnetism as a motive power,

without regard to the particular process with which it was connected in the patent, could not be

claimed, but that its use in that connection could.”132 The Court found that Bell’s claim, unlike

Morse’s, did not reach uses of electricity to transmit speech that are “distinct from the particular

process with which it is connected in [Bell’s] patent,” and upheld the claim, so construed.133

Twentieth Century

In the first half of the 20th century, the Court decided two major cases on the patentability of

natural phenomena. In American Fruit Growers v. Brogdex Co., the Court rejected patent claims

on citrus fruit treated with a solution of borax to render it resistant to mold.134 The Court held that

treated fruit was not a “manufacture” under Section 101, but a patent-ineligible “natural article”;

treatment with borax did not effect a “change in the name, appearance, or general character of the

fruit” or imbue it with a “new or distinctive form, quality, or property.”135 In Funk Brothers Seed

Co. v. Kalo Inoculant Co., the Court rejected patent claims on an inoculant for leguminous plants

consisting of multiple species of bacteria, where the particular bacterial strains were selected to

avoid inhibiting each other (as prior multispecies combinations had).136 Because the patentee’s

combination “produces no new bacteria [and] no change in the six species of bacteria,” Justice

William Douglas’s majority opinion held that it was only “the discovery of some of the

handiwork of nature and hence is not patentable.”137

From 1972 to 1981, the Supreme Court decided four patentable subject matter cases.138 In

Gottschalk v. Benson, the Court held that an algorithm for converting binary-coded decimal

numerals into pure binary numerals (either by hand, or, more practically, on a computer) was

patent-ineligible.139 Justice Douglas reasoned that “one may not patent an idea” and that

upholding this patent would “wholly pre-empt the mathematical formula and in practical effect

would be a patent on the algorithm itself.”140 Second, in Parker v. Flook, the Court rejected a

129 Id. at 787.

130 102 U.S. 707, 728–30 (1880).

131 Dolbear v. Am. Bell Tel. Co. (The Telephone Cases), 126 U.S. 1, 531, 534–35 (1888).

132 Id. at 534.

133 Id. at 534–35.

134 283 U.S. 1, 6, 11–12 (1931).

135 Id. at 11–12.

136 333 U.S. 127, 130–32 (1948).

137 Id.

138 Three of these four (Benson, Flook, and Diehr), which concern the patentability of inventions relating to

mathematical formulas and computers, are often referred to as a “trilogy.” See, e.g., Michel, supra note 20, at 1755;

Menell, supra note 112, at 1290. This usage leaves out Chakrabarty, which was also decided in the same time frame,

because that case concerned the exception for products of nature.

139 409 U.S. 63, 64, 71–73 (1972).

140 Id. at 71–72.

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patent on a method for updating alarm limits during catalytic conversion of hydrocarbons (such as

petroleum), which relied in part on a mathematical formula, because the only novel feature of the

method was the mathematical formula.141 Third, in Diamond v. Chakrabarty, the Court upheld a

patent on a genetically engineered bacterium useful in breaking down oil (e.g., in cleaning up oil

spills).142 Chief Justice Warren Burger distinguished American Fruit Growers and Funk Brothers

because this bacterium, although a living organism, was human-made and possessed “markedly

different characteristics from any [bacteria] found in nature.”143 Finally, in Diamond v. Diehr, the

Court distinguished Flook to uphold a patent on a process for molding synthetic rubber that relied

on a mathematical formula (the Arrhenius equation).144 Justice William Rehnquist’s majority

opinion reached back to Cochrane v. Deener, holding that the process at issue was patentable

because it transformed an article (uncured rubber) into a different state or thing.145 Even though

the method used a mathematical formula, the patent in Diehr did not claim the formula itself and

would not “pre-empt the use of that equation” in other fields.146

After Diehr, the Court did not decide a major patentable subject matter case for nearly 30

years.147 Development of patent-eligible subject matter law was mainly left to the Federal Circuit,

whose decisions generally expanded patent-eligible subject matter,148 such that by the late 1990s

Section 101 became perceived as “a dead letter.”149

141 437 U.S. 584, 585, 591–92 (1978).

142 447 U.S. 303, 305, 309–10 (1980).

143 Id. at 310.

144 450 U.S. 175, 177, 183–93 (1981).

145 Id. at 184.

146 Id. at 187. In the view of many commentators, Diehr effectively overturned Flook (or at least some statements in

Flook) without explicitly saying so. See, e.g., Michel, supra note 20, at 1756 (“Diehr, to my eye, overruled Flook five

to four.”); Menell, supra note 112, at 1298 (“Justice Rehnquist [in Diehr] effectively overrode Flook’s statutory subject

matter test.”); BCLT Report, supra note 16, at 554 (“Flook was effectively overruled three years later in Diamond v.

Diehr . . . .”); Athena Diagnostics, Inc. v. Mayo Collaborative Servs., 927 F.3d 1333, 1346 (Fed. Cir. 2019) (Chen, J.,

concurring in the denial of rehearing en banc) (“Given Diehr’s evident disagreement with Flook’s analysis, Diehr, as

the later opinion, was widely understood to be the guiding, settled precedent on § 101 for three decades.”); Dennis

Crouch, Revival of Parker v. Flook II, PATENTLYO (Jan. 4, 2018), https://patentlyo.com/patent/2018/01/revival-parkerflook.html (presenting data showing that courts rarely cited Flook between 1982 and 2007).

The Supreme Court does not appear to view matters this way, however—it continues to cite and rely on Flook as good

law. See, e.g., Alice Corp. Pty. v. CLS Bank Int’l, 573 U.S. 208, 218, 222 (2014).

147 See Lemley et al., supra note 21, at 1317; Menell, supra note 112, at 1298. There are two partial exceptions to this

generalization. The first is J.E.M. Ag Supply, Inc. v. Pioneer Hi-Bred Int’l, Inc., in which the Court held that humanmade plant varieties were patentable under Section 101. 534 U.S. 124, 127 (2001). However, that case turned not on

general patent-eligibility principles, but on whether two specialized statutes for protection of plant varieties precluded

utility patents on plants under the general provisions of Section 101. Id. at 132–44. Second, although the Supreme

Court ultimately did not decide the case, Justice Breyer’s 2006 dissent from the dismissal of a writ of certiorari as

improvidently granted in Laboratory Corporation of America Holdings v. Metabolite Laboratories, Inc., served as an

important signal of the Court’s renewed interest in patentable subject matter. See 548 U.S. 124 (2006). Metabolite

involved claims for diagnosing vitamin deficiencies, much like the claims the Supreme Court would address years later

in Mayo, when the Court largely adopted the reasoning of Justice Breyer’s Metabolite dissent. See id. at 129, 135–38.

148 See generally Menell, supra note 112, at 1298–99; Julie E. Cohen & Mark A. Lemley, Patent Scope and Innovation

in the Software Industry, 89 CAL. L. REV. 1, 9–14 (2001). The canonical examples are In re Alappat, 33 F.3d 1526,

1542–45 (Fed. Cir. 1994) (en banc) (permitting software claims if tied to a machine, including a programmed generalpurpose computer) and State Street Bank v. Signature Financial Group, 149 F.3d 1368, 1373 (Fed. Cir. 1998) (Rich, J.)

(holding that computer-implemented business methods are patentable if tied to a machine that produces “a useful,

concrete and tangible result”). Both cases were later abrogated. See In re Bilski, 545 F.3d 943, 959–60 (Fed. Cir. 2008)

(en banc), aff’d, sub nom. Bilski v. Kappos, 561 U.S. 593 (2010).

149 Lemley et al., supra note 21, at 1318 (“[A]fter 1998, patentable subject matter was effectively a dead letter”).

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The Modern Alice/Mayo Framework

In 2010, the Supreme Court reentered the field of patent-eligible subject matter, deciding four

cases on the issue within five years.150 These cases established the two-step Alice/Mayo test for

patentable subject matter.

The first step of the Alice/Mayo test addresses whether the patent claims are “directed to” an

ineligible concept: a law of nature, a natural phenomenon, or an abstract idea.151 The inquiry at

step one focuses on the “claim as whole.”152 To be “directed to” an eligible concept at step one of

Alice/Mayo, the claims must not simply involve a patent-ineligible concept.153 Rather, the “focus

of the claims” must be a patent-ineligible concept, and not the improvement of a technological

process.154 If the patent claims are not directed to an ineligible concept, then the subject matter is

patent-eligible.155

If the claims are directed to an ineligible category, then the invention is not patentable unless the

patent claims have an “inventive concept” under the second step of the Alice/Mayo test.156 Step

two of Alice/Mayo considers the elements of each patent claim both individually and as an

ordered combination in the search for an “inventive concept”—additional elements that

“transform the nature of the claim” into a patent-eligible application of an ineligible concept.157

To have an “inventive concept,” the patent claims must contain elements “sufficient to ensure that

the patent in practice amounts to significantly more than a patent upon the [ineligible concept]

itself.”158 Claim limitations that are “conventional, routine and well understood,” such as generic

computer implementation, cannot supply an inventive concept.159

Bilski v. Kappos, the first in the series of Supreme Court cases that developed what became

known as the Alice/Mayo framework, concerned a patent on a business method for hedging

against price-fluctuation risks in energy and commodity markets.160 The Federal Circuit had held

that this method was not patentable as a “process” under Section 101 because it failed the

“machine-or-transformation test”—that is, it was neither “tied to a particular machine or

apparatus” nor “transform[ed] a particular article into a different state or thing.”161 All nine

members of the Supreme Court agreed with that result—that the business method at issue was not

150 Bilski v. Kappos, 561 U.S. 593 (2010); Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66 (2012);

Ass’n for Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576 (2013); Alice Corp. Pty. v. CLS Bank Int’l, 573

U.S. 208 (2014).

151 Alice, 573 U.S. at 217.

152 Athena Diagnostics, Inc. v. Mayo Collaborative Servs., 915 F.3d 743, 750 (Fed. Cir. 2019) (citing Elec. Power Grp.,

v. Alstom S.A., 830 F.3d 1350, 1353 (Fed. Cir. 2016)).

153 Enfish, LLC v. Microsoft Corp., 822 F.3d 1327, 1335–36 (Fed. Cir. 2016).

154 Id.; see also Athena, 915 F.3d at 750 (“To determine whether a claim is directed to an ineligible concept, we have

frequently considered whether the claimed advance improves upon a technological process or merely an ineligible

concept, based on both the written description and the claim.”) (citations omitted).

155 Alice, 573 U.S. at 217.

156 Id.

157 Alice, 573 U.S. at 217–28 (quotations omitted).

158 Id. (quoting Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 73 (2012)).

159 Ariosa Diagnostics, Inc. v. Sequenom, Inc., 788 F.3d 1371, 1378 (Fed. Cir. 2015); accord Alice, 573 U.S. at 225;

Mayo, 566 U.S. at 79 (“Purely ‘conventional or obvious’ ‘[pre]-solution activity’ is normally not sufficient to transform

an unpatentable law of nature into a patent-eligible application of such a law.” (quoting Parker v. Flook, 437 U.S. 584,

590 (1978))).

160 Bilski, 561 U.S. at 598–99.

161 In re Bilski, 545 F.3d 943, 954 (Fed. Cir. 2008) (en banc) (Michel, C.J.).

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patent-eligible—but differed significantly as to their reasoning. Writing for five Justices, Justice

Anthony Kennedy held that the machine-or-transformation test was not the “sole test” for

determining whether a process is patent-eligible but still “a useful and important clue.”162 While

the majority rejected the “atextual” notion that business methods were categorically unpatentable

under Section 101,163 it relied on Benson and Flook to conclude that this particular patent

attempted to claim an unpatentable abstract idea: the “concept of hedging risk.”164 Concurring

only in the judgment, Justice John Paul Stevens wrote for four Justices who would have held,

based on the history of the Patent Act and its constitutional purpose, that business methods were

always patent-ineligible.165

In Mayo Collaborative Services v. Prometheus Laboratories, the Court addressed the scope of the

“law of nature” exception.166 The patent in Mayo claimed a method for measuring metabolites in

human blood in order to calibrate the dosage of thiopurine drugs in the treatment of autoimmune

disorders.167 Writing for a unanimous Court, Justice Stephen Breyer’s opinion held that the patent

claims were addressed to a law of nature: “namely, relationships between concentrations of

certain metabolites in the blood and the likelihood that a dosage of a thiopurine drug will prove

ineffective or cause harm.”168 Because the claims were little “more than an instruction to doctors

to apply the applicable laws when treating their patients,” the patent lacked any inventive concept

and was held to be patent-ineligible.169

The next case, Association for Molecular Pathology v. Myriad Genetics, Inc., concerned the

applicability of the “natural phenomena” exception to the patentability of human DNA.170 The

inventor in Myriad had discovered the precise location and genetic sequence of two human genes

associated with an increased risk of breast cancer.171 Based on this discovery, the patentee claimed

two molecules associated with the genes: (1) an isolated DNA segment and (2) a complementary

DNA (cDNA) segment, in which the nucleotide sequences that do not code for amino acids were

removed in the laboratory.172 Justice Clarence Thomas’s unanimous opinion in Myriad held that

isolated DNA segments were nonpatentable products of nature because the patent claimed

naturally occurring genetic information.173 The Court held, however, that cDNA, as a synthetic

molecule distinct from naturally occurring DNA, was patentable even though the underlying

nucleotide sequence was dictated by nature.174

Most recently, Alice Corp. v. CLS Bank International examined the scope of the “abstract idea”

category of nonpatentable subject matter.175 Alice concerned a patent on a system for mitigating

162 Bilski, 561 U.S. at 604.

163 Id. at 609.

164 Id. at 609–12.

165 Id. at 626–57 (Stevens, J., concurring in the judgment).

166 566 U.S. 66, 77 (2012).

167 Id. at 73–75.

168 Id. at 77.

169 Id. at 79.

170 569 U.S. 576 (2013).

171 Id. at 579.

172 Id. at 580–85.

173 Id. at 591–94. Justice Antonin Scalia joined the opinion save for the “fine details of molecular biology,” as he found

himself “unable to affirm those details on my own knowledge or even my own belief.” Id. at 596 (Scalia, J., concurring

in part and in the judgment).

174 Id. at 594–95.

175 573 U.S. 208 (2014).

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“settlement risk”—the risk that only one party to a financial transaction will pay what it owes—

using a computer as an intermediary.176 The Court first held, relying on Bilski, that the invention

was directed at “the abstract idea of intermediated settlement.”177 Although this idea was

implemented on a computer (which is, of course, a physical machine), the patent lacked an

inventive concept because the claims merely “implement[ed] the abstract idea of intermediated

settlement on a generic computer.”178

Table 1 summarizes the facts and holding of the Supreme Court’s major patentable subject matter

cases, in reverse chronological order.

Table 1. Major Supreme Court Decisions on Patentable Subject Matter

Case Citation

Claimed Inventions

Holding and Rationale

Alice Corp. Pty. v. CLS

Bank Int'l, 573 U.S.

208 (2014)

Computer-implemented method and

system for mitigating settlement risk in

financial transactions using a third-party

intermediary

Ineligible: The claims are drawn to the

abstract idea of intermediated settlement;

implementation on a generic computer does

not transform an ineligible abstract idea into a

patent-eligible invention.

Ass'n for Molecular

Pathology v. Myriad

Genetics, Inc., 569

U.S. 576 (2013)

Isolated human DNA segments and

exon-only complementary DNA (cDNA)

segments corresponding to genes

discovered to be linked to an increased

risk of breast cancer

Certain Claims Ineligible: Isolated human

DNA segments are patent-ineligible because

the nucleotide sequence is a product of

nature and isolation from the rest of the

genome is insufficient to render them

patentable; however, cDNA is patentable

because it is not naturally occurring.

Mayo Collaborative

Servs. v. Prometheus

Labs., Inc., 566 U.S.

66 (2012)

Method for optimizing dosage of

thiopurine drugs for treating

autoimmune disease, by administering

the drug, measuring a metabolite, and

adjusting the dosage based on the

measurement

Ineligible: The relationship between the

concentration of particular metabolites in the

blood and a drug’s effectiveness is directed to

a law of nature, and the claims lack an

inventive concept beyond conventional postsolution activity.

Bilski v. Kappos, 561

U.S. 593 (2010)

Business method for hedging against

price-fluctuation risks in energy and

commodity markets

Ineligible: Although business methods are

not categorically patent-ineligible, the process

at issue was not patentable because it claimed

the abstract idea of hedging risk.

J.E.M. Ag. Supply v.

Pioneer Hi-Bred Int’l,

Inc., 534 U.S. 124

(2001)

Human-developed inbred and hybrid

corn plant varieties and seeds

Eligible: Newly developed plant varieties are

human-made manufactures or compositions

of matter, even though protection may also

be available under the Plant Patent Act or the

Plant Variety Protection Act.

Diamond v. Diehr, 450

U.S. 175 (1981)

Process for molding raw, uncured

synthetic rubber into cured products,

relying on the Arrhenius equation and a

programmed computer to calculate the

curing time

Eligible: The invention does not claim a

mathematical formula or a law of nature as

such, but applies a natural law to a particular

industrial process that transforms an article

into a different state or thing.

Diamond v.

Chakrabarty, 447 U.S.

303 (1980)

Genetically engineered bacterium

capable of breaking down components in

crude oil

Eligible: The genetically engineered

bacterium was not naturally occurring and

possessed markedly different characteristics

from any bacteria found in nature.

176

Id. at 212.

177 Id. at 221.

178 Id. at 225.

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Case Citation

Claimed Inventions

Holding and Rationale

Parker v. Flook, 437

U.S. 584 (1978)

Method of updating alarm limits used in

catalytic conversion of hydrocarbons

(e.g., in oil refining) relying on a

mathematical formula

Ineligible: The only novel feature of the

invention was a mathematical formula,

conventionally applied to a specific field.

Gottschalk v. Benson,

409 U.S. 63 (1972)

Method for converting binary-coded

decimal numerals into pure binary

numerals on digital computer

Ineligible: The patent claims cover all

practical uses of a mathematical algorithm and

would, in effect, amount to a patent on the

algorithm itself.

Funk Bros. Seed Co. v.

Kalo Inoculant Co.,

333 U.S. 127 (1948)

Inoculant for leguminous plants

comprising several strains of mutually

noninhibitive species of bacteria to

improve nitrogen fixation

Ineligible: Each bacterial strain is naturally

occurring, and discovery of the noninhibitive

qualities of certain strains was not invention

but merely the discovery of a nonpatentable

natural phenomenon.

Mackay Radio & Tel.

Co. v. Radio Corp. of

Am., 306 U.S. 86

(1939)179

Radio antenna in which the angle of the

wires and their length are determined by

a mathematical formula

Assumed to be patentable: Although a

mathematical expression of a scientific truth

is not patentable, a novel and useful structure

created with the aid of knowledge of scientific

truth may be patentable.

Am. Fruit Growers v.

Brogdex Co., 283 U.S.

1 (1931)

Citrus fruit treated with borax solution

to render it resistant to mold

Ineligible: Treatment with borax did not

transform the fruit (a product of nature) into

a manufacture with a new or distinctive form,

quality, or property.

The Telephone Cases,

126 U.S. 1 (1888)

Method and apparatus for transmitting

sound telegraphically by causing

electrical undulations, similar to air

vibrations accompanying speech and

other sounds

Eligible: The patentee did not claim all uses

of electricity to transmit speech at a distance,

but only the particular process and apparatus

disclosed in the patent.

Tilghman v. Proctor,

102 U.S. 707 (1881)

Process for separating fat into glycerin

and fatty acids using water, pressure, and

heat

Eligible: New and useful manufacturing

processes are “arts” that may be patented

independently of the apparatus used.

Cochrane v. Deener,

94 U.S. 780 (1877)

Improved industrial process for

manufacturing flour

Eligible: A process (“a series of acts,

performed upon the subject-matter to be

transformed and reduced to a different state

or thing”) is patentable independent of the

machinery used.

Rubber-Tip Pencil Co.

v. Howard, 87 U.S.

(20 Wall.) 498

(1874)

Rubber cap with cavity designed to be

attached to lead pencils for convenient

use as an eraser

Ineligible: An “idea of itself” (here, the idea

of attaching a piece of rubber to the end of a

pencil for use as an eraser) is not patentable.

Corning v. Burden, 56

U.S. (15 How.) 252

(1854)

Machine for rolling puddle balls and

other masses of iron used in the

manufacture of iron products

Eligible: The patentee did not claim the

function or abstract effect of a machine, but

only the machine that produced the result.

179 Although Mackay Radio is widely quoted in subsequent jurisprudence for the proposition that useful applications of

laws of nature are patentable, see, for example, Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 71

(2012); Diamond v. Diehr, 450 U.S. 175, 188 (1981), Justice Harlan Stone’s statement is dicta because the Court

merely “assume[d], without deciding” that the invention was patentable, ruling instead on grounds of noninfringement,

see Mackay Radio, 306 U.S. at 94, 101.

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Case Citation

Claimed Inventions

Holding and Rationale

O'Reilly v. Morse, 56

U.S. (15 How.) 62

(1854)180

Any use of electro-magnetism for

printing intelligible characters, signs, or

letters, at a distance

Ineligible: The discovery of a scientific

principle is not patentable, nor can a patentee

claim a useful result in the abstract, apart

from the particular process or machine by

which the result is accomplished.

Le Roy v. Tatham, 55

U.S. (14 How.) 156

(1853)181

Machinery for manufacturing wrought

metal pipes exploiting a newly

discovered property of lead

Potentially patentable: Although a

principle in the abstract is not patentable, a

practical application of such a principle to a

new and useful end is patentable.

Source: CRS.

The Debate Over Alice/Mayo and Section 101

Reform

A substantial group of patent law stakeholders, including inventors, academics, industry

representatives, patent attorneys, current and former Federal Circuit judges, and former USPTO

officials, has criticized the Alice/Mayo framework on various grounds.182 Other patent law

stakeholders defend the Supreme Court’s Section 101 decisions.183

Criticisms of the Alice/Mayo Framework

Generally, critics of the Court’s patentable subject matter jurisprudence raise four principal

concerns. First, the Alice/Mayo framework is criticized as excessively vague, subjective, and

unpredictable in application. For example, the Federal Circuit has stated that when determining

whether a patent claim is “directed to” an ineligible concept at step one, courts must determine

whether the “focus” of the claims is on that concept.184 At the same time, the Federal Circuit has

cautioned that this “focus” must be articulated “with enough specificity to ensure the step one

180 The specific doctrinal basis of O’Reilly v. Morse is unclear, as the Court speaks in language that, when cast in

modern terms, sounds at times like enablement and at times like patentable subject matter. Compare 56 U.S. at 113

(“The court is of opinion that the claim is too broad . . . .”) with id. at 116 (“[T]he discovery of a principle in natural

philosophy or physical science, is not patentable.”). Many patent scholars regard Morse as a case not about Section 101

but about enablement under Section 112 of the modern Patent Act. See, e.g., Taylor, supra note 20, at 205 (“In modern

terms, it is quite clear that the problem with Claim 8 in Morse’s patent was based on the enablement and written

description requirements located in § 112 and not in § 101.”); Lefstin, supra note 113, at 597 (“Morse is about

disclosure and scope, not patent-eligible subject matter.”). The Supreme Court, however, appears to regard Morse as

primarily a subject matter decision. See, e.g., Mayo, 566 U.S. at 70, 73 (citing to Morse to support notion that “laws of

nature” or claims that “preempt the use of a natural law” are “not patentable”).

181 Statements in Le Roy to the effect that a “principle, in the abstract” is not patentable, but a practical application of

such a principle may be patentable, 55 U.S. at 174–75, are widely quoted and influential in subsequent American

jurisprudence. See supra note 115. Nonetheless, because the result in Le Roy turned primarily on claim construction,

see 55 U.S. at 176, these general statements were dicta and did not entail the holding of the case.

182

See infra “Criticisms of the Alice/Mayo Framework.”

183 See infra “Defenses of the Alice/Mayo Framework.”

184 Elec. Power Grp. v. Alstom S.A., 830 F.3d 1350, 1353 (Fed. Cir. 2016).

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inquiry is meaningful.”185 The appropriate level of specificity can vary from patent to patent and

from judge to judge.186

Thus, in the view of many stakeholders, the Supreme Court’s patentable subject matter case law

and the Federal Circuit’s implementation of the Alice/Mayo framework fail to articulate

“objective, predictable criteria” for making patent-eligibility determinations.187 Key terms, such

as what an “abstract idea” is, or precisely how claim elements can make an invention

“significantly more” than an ineligible category (the “inventive concept”), are largely left

undefined, making it difficult for patent applicants and litigants to know whether their patent

claims will survive judicial scrutiny.188 Moreover, the Federal Circuit has explicitly recognized

that the two steps of the analysis are not clearly defined and may overlap.189 As a result, many

observers characterize the court’s Section 101 jurisprudence as a “highly subjective,” “I know it

when I see it” approach.190 This subjectivity, in the view of critics, injects unpredictability and

uncertainty into whether an invention is of a type that is patentable.191

Second, the Alice/Mayo framework is criticized as legally flawed on various grounds. Some

stakeholders argue that the Alice/Mayo framework misinterprets Section 101, imposing “extrastatutory” requirements for patent eligibility, contrary to congressional intent or the constitutional

purpose of patent law.192 Others argue that Mayo’s requirement of an “inventive concept” rests on

a historically inaccurate understanding of 19th century English patent law, first imported into

185 Thales Visionix Inc. v. United States, 850 F.3d 1343, 1347 (Fed. Cir. 2017).

186 See Visual Memory LLC v. NVIDIA Corp., 867 F.3d 1253, 1262 (Fed. Cir. 2017) (Hughes, J., dissenting)

(disagreeing with the majority over whether characterizing the claims as directed to “categorical data storage” views

the invention “at an unduly ‘high level of abstraction’”) (quoting Enfish, LLC v. Microsoft Corp., 822 F.3d 1327, 1337

(Fed. Cir. 2016)).

187

USPTO PSM REPORT, supra note 16, at 29.

188 See id. at 30 (describing comments that the Alice/Mayo test “fails to define crucial terms, such as ‘abstract’ and

‘substantially more’”); Taylor, supra note 20, at 231 (“[N]o one really knows what an inventive concept is.”); Lemley

et al., supra note 21, at 1316 (“[N]o one understands what makes an idea ‘abstract,’ and hence ineligible . . . .”);

Morris, supra note 106, at 68 (arguing that the judicially created patentable subject matter decisions are “merely post

hoc rationalizations”). Some Supreme Court Justices have echoed this criticism. See, e.g., Bilski v. Kappos, 561 U.S.

593, 621 (2010) (Stevens, J., concurring in the judgment) (“The Court . . . never provides a satisfying account of what

constitutes an unpatentable abstract idea.”); Fred Funk Seed Bros. Co. v. Kalo Inoculant Co., 333 U.S. 127, 134–35

(1948) (Frankfurter, J., concurring) (“It only confuses the issue, however, to introduce such terms as ‘the work of

nature’ and the ‘laws of nature.’ For these are vague and malleable terms infected with too much ambiguity and

equivocation.”). To some extent, uncertainty in Section 101 is not a new phenomenon. See, e.g., Duffy, supra note 113,

at 623–38 (reviewing history of failed patentable subject matter rules and observing that “instability in the law of

patentable subject matter” is a recurring issue). However, at least in the decade before Mayo, uncertainty was less

practically important for patentees because courts and the USPTO only “rarely” rejected patents based on Section 101.

See BCLT Report, supra note 16, at 575–76 (reviewing data showing a “dramatic” increase in the number of Section

101 district court decisions following Mayo, with a “10-fold” increase following Alice).

189 Elec. Power Grp., 830 F.3d at 1353 (“[T]he two stages are plainly related: not only do many of our opinions make

clear that the two stages involve overlapping scrutiny of the content of the claims, but we have noted that there can be

close questions about when the inquiry should proceed from the first stage to the second.”) (citations omitted).

190 See, e.g., USPTO PSM REPORT, supra note 16, at 30 (quoting stakeholder view that Alice/Mayo is “hopelessly

subjective”); Taylor, supra note 20, at 227–30 (arguing that Alice/Mayo framework has “no objective guidance” and

“leaves the determination of eligibility to the unconstrained, subjective opinion of a patent examiner or judge”); Klein,

supra note 106, at 288 (criticizing patentable subject matter case law as amounting to “an ‘I know it when I see it’

approach”).

191 See, e.g., BCLT Report, supra note 16, at 561 (describing “uncertainty and confusion resulting from the Court’s

recent [patentable subject matter] jurisprudence”); accord USPTO PSM REPORT, supra note 16, at 30–31 (describing

views that the Alice/Mayo test yields “unpredictable” and “inconsistent” results).

192 See USPTO PSM REPORT, supra note 16, at 28; Klein, supra note 106, at 289–91 (criticizing the three judicially

created categorical exclusions as “extra-statutory” and proposing test that focuses on text of Section 101).

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American jurisprudence in cases such as Le Roy and Morse.193 Finally, many commentators and

stakeholders argue that the Alice/Mayo framework confuses patent law by conflating eligibility

under Section 101 with policy concerns—such as the obviousness of the invention and claim

breadth—that are better addressed by other provisions in the Patent Act, such as Sections 102,

103, and 112.194 For example, patent claims have been found to lack an inventive concept at

Alice/Mayo step two where they implement an abstract idea on conventional computer

hardware.195 Issues about what was “conventional” or “well-understood” at the time of the

invention, however, are questions usually reserved for novelty or nonobviousness analysis.196

Third, the Alice/Mayo framework is alleged to have detrimental effects on incentives to innovate,

especially in the biotechnology and computer software industries. Given the patent claims at issue

in Alice (a computer-implemented business method), Myriad (an isolated human DNA segment),

and Mayo (a drug dose optimization method), most observers agree that these two industries have

been the most affected by the Supreme Court’s Section 101 rulings.197 In the biotechnology

industry, stakeholders argue that the Alice/Mayo framework has limited their ability to obtain

patents on diagnostic methods and kits, personalized medicine, and isolated natural substances.198

Views in the computer industry are “sharply divided,” but at least some stakeholders argue that

Alice has devalued their patents and created uncertainty for their business.199 In both fields, some

stakeholders argue that the law of Section 101 is reducing incentives to innovate in these areas

and driving investment elsewhere.200

Finally, the uncertainty and unpredictability caused by Alice/Mayo is alleged to put the United

States at a disadvantage relative to international competitors. Some stakeholders argue that U.S.

competitiveness may be harmed because a lack of patent availability will drive investment in

certain industries to other countries where such inventions are more clearly patent-eligible.201

Lefstin, supra note 113, at 565 (arguing that Alice/Mayo test’s “inventive application” requirement rests on a “basic

misapprehension” of the 19th century English case cited by the Supreme Court); USPTO PSM REPORT, supra note 16,

at 27–28 (same).

194 See USPTO PSM REPORT, supra note 16, at 31–32; Taylor, supra note 20, at 157 (“[T]he current approach to

determining patent eligibility confuses the relevant policy concerns underlying numerous discrete patent law

doctrines.”); see also Risch, supra note 21, at 594 (arguing that the Court’s patentable subject matter doctrine would be

more consistent and rigorous if replaced with a strict application of other patentability doctrines such as obviousness,

novelty, utility, inventorship, written description, and enablement). This criticism has been echoed by Supreme Court

Justices. See Parker v. Flook, 437 U.S. 584, 600 (1978) (Stewart, J., dissenting) (“[The majority] strikes what seems to

me an equally damaging blow at basic principles of patent law by importing into its inquiry under 35 U.S.C. § 101 the

criteria of novelty and inventiveness.”).

195 See, e.g., Elec. Power Grp., 830 F.3d at 1355.

196 See, e.g., Berkheimer v. HP Inc., 881 F.3d 1360, 1368–69 (Fed. Cir. 2018) (noting that Alice/Mayo step two

determination of whether claims are “well-understood, routine and conventional” overlaps with Section 102 novelty

inquiry).

197 USPTO PSM REPORT, supra note 16, at 34–35 (“Among members of the public, there was a general consensus that

two industries have been most directly affected [by the Alice/Mayo framework]: life sciences and computer-related

technologies.”); see also BCLT Report, supra note 16, at 582–85 (examining the Alice/Mayo framework’s effects on

diagnostics, personalized medicine, biosciences, software, and information technology).

198 See USPTO PSM REPORT, supra note 16, at 34–35; BCLT Report, supra note 16, at 582–84.

199 See USPTO PSM REPORT, supra note 16, at 37–38 (characterizing the views on Alice/Mayo in the computer

industry as “sharply divided”); BCLT Report, supra note 16, at 582–84.

200 See USPTO PSM REPORT, supra note 16, at 35, 38; BCLT Report, supra note 16, at 583.

201 See, e.g., Stoll, supra note 23 (“The courts’ focus on subject matter eligibility as a mechanism to deny patents for

[inventions in diagnostics and personalized medicine] will drive investment into research in these technologies to other

areas. We will lose our edge in the world . . . .”); accord USPTO PSM REPORT, supra note 16, at 34; Kevin Madigan &

Adam Mossoff, Turning Gold into Lead: How Patent Eligibility Doctrine Is Undermining U.S. Leadership in

(continued...)

193

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Others argue that one effect of Alice/Mayo is a loss of any patent protection for certain inventions,

which will enable competitors to “free ride” off of American innovation.202

Defenses of the Alice/Mayo Framework

Defenders of the current law of Section 101 respond that these criticisms of Alice/Mayo are

overstated, or that the Supreme Court’s reinvigoration of Section 101 has important benefits for

the patent system. As to the subjective or unpredictable nature of Section 101 doctrine, there is

some empirical evidence that the Alice/Mayo framework is not as unpredictable as is sometimes

claimed.203 Some commentators also observe that uncertainty in patentable subject matter law is

hardly a new phenomenon,204 and may even be “inevitable.”205 A subjective or “amorphous”

approach to patentable subject matter, on this view, may have certain benefits, including

flexibility and adaptability to new technologies.206 Moreover, even if one views the current state

of the law as unacceptably vague, courts may eventually clarify or change Section 101 doctrine in

line with the long history of common law development in this area.207

As to the legal correctness of Alice/Mayo, defenders of the framework note that while the

judicially created categories are not directly grounded in the text of Section 101, they have been

treated as part of the law “as a matter of statutory stare decisis going back 150 years.”208 As to

Mayo’s reliance on 19th century English patent law, some commentators defend the Supreme

Court’s “inventive application” requirement as a faithful reading of this precedent.209 Finally,

although the Alice/Mayo framework may overlap with other patent law doctrines, several

commentators and judges of the Federal Circuit argue that Section 101 serves purposes distinct

Innovation, 24 GEO. MASON L. REV. 939, 942–44 (2017) (expressing “concern about the U.S. conceding its gold

standard patent system to China and Europe” because of the uncertainty of the Alice/Mayo framework).

202 See, e.g., Davis, supra note 23 (quoting former USPTO Director David Kappos as stating that international

competitors “no longer have to steal U.S. technology in [biotech and software], since they can now take it for free”).

203 See Jason D. Reinecke, Is the Supreme Court’s Patentable Subject Matter Test Overly Ambiguous? An Empirical

Test, 2019 UTAH L. REV. 581, 583 (2019) (empirical study indicating that while “the [Alice/Mayo] test is likely not a

beacon of absolute clarity, it is not completely amorphous,” as patent prosecutors correctly predicted judicial results

67.3% of the time based only on claim language).

204 See, e.g., Duffy, supra note 113, at 623–38 (reviewing 100-year history of failed rules and tests for patentable

subject matter and observing that “instability in the law of patentable subject matter” is a recurring issue) & id. at 616

(citing 19th century treatise writers noting difficulty and complexity of the patentable subject matter); Risch, supra note

21, at 591 (criticizing, in 2008, the “currently confused and inconsistent jurisprudence of patentable subject matter”);

Donald S. Chisum, The Patentability of Algorithms, 47 U. PITT. L. REV. 959, 992 (1986) (noting “confusion and

arbitrary distinctions” in the law of the patentability of computer software resulting from the Benson decision).

205 Morris, supra note 106, at 107 (arguing that the Court’s “intuitive” approach to patentable subject matter

determinations is “inevitable”).

206 Id. at 107–09 (arguing that intuitive approach to Section 101 may be “desirable” because “there is simply no other

more rigorous and yet durable way of identifying the proper boundaries for patentable subject matter” and “vagueness

provides the flexibility necessary to adjust future technological developments”); Duffy, supra note 113, at 639 (“[T]he

traditional doctrines of patentable subject matter—the prohibition against patenting abstract ideas, natural phenomena,

and principles of nature—have survived because . . . they have been amorphous.”).

207 See USPTO PSM REPORT, supra note 16, at 23–24 (expressing stakeholder views that the Court’s decisions are part

of the normal common law development of Section 101, and that the Federal Circuit’s subsequent development of the

law may be “headed in the right direction”).

208 Bilski v. Kappos, 561 U.S. 593, 602 (2010) (citing Le Roy v. Tatham, 55 U.S. (14 How.) 156, 174–75 (1853)).

209 See Brief of Nine Law Professors as Amicus Curiae in Support of Petitioners at 8–16; Mayo Collaborative Servs. v.

Prometheus Labs., Inc., 566 U.S. 66 (2012) (No. 10-1150), 2011 WL 4071921.

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from Sections 102, 103, and 112.210 For example, even if the invention in Myriad—an isolated

human DNA sequence discovered to be linked to increased breast cancer risk—was novel,

nonobvious, and sufficiently disclosed, some commentators would still argue that the invention

should not be patented based on harm to future innovation or moral concerns about patenting

human DNA.211

Regarding the alleged detrimental effects of the Court’s Section 101 decisions on innovation,

some stakeholders point to countervailing benefits either generally or in certain industries. In

particular, some stakeholders in industries (such as computer software) affected by litigation by

patent assertion entities212 argue that Section 101 is a useful and important tool for weeding out

overly broad or vague patents at the outset of litigation.213 Other commentators point to general

utilitarian or moral benefits of robust exclusions for patents on basic discoveries in science and

nature.214

Lastly, in response to concerns about the Alice/Mayo framework’s effect on international

competitiveness, some commentators assert that these changes are good for the United States as a

geopolitical matter.215 In particular, restricted patent-eligibility standards may benefit U.S.

consumers if a lack of patent protection leads to increased competition and lower prices for

certain products without harming innovation.216

Views on the Purposes of Section 101

There is a long-running debate over the functions and purposes that Section 101 serves in the

patent system. For its part, the modern Supreme Court has largely settled on the “preemption

rationale” for the judicially created subject matter exclusions. These decisions assert that abstract

ideas, laws of nature, and natural phenomena should not be patentable because permitting a

monopoly on the “‘basic tools of scientific and technological work’ . . . might tend to impede

innovation more than it would tend to promote it,”217 in that such patents would “significantly

impede future innovation.”218 The gist of the preemption rationale is that Section 101 functions to

210 See, e.g., Morris, supra note 106, at 113 (“To be sure, patentable subject matter overlaps with and serves some of

the same purposes as the other patentability requirements . . . . But only patentable subject matter serves to distinguish

patentable technology from unpatentable discoveries, information, and human thought and activity.”); Lemley et al.,

supra note 21, at 1330–32 (distinguishing purpose of Section 101 from Section 112); accord Mayo, 566 U.S. at 90–91;

Athena Diag., Inc. v. Mayo Collaborative Servs., 927 F.3d 1333, 1337–39 (Fed. Cir. 2019) (Dyk, J., concurring in the

denial of rehearing en banc).

211

See generally infra “Views on the Purposes of Section 101.”

212 A patent assertion entity, sometimes called a nonpracticing entity or (pejoratively) a “patent troll,” is a loose term

for an individual or organization that seeks to license or litigate patents, but does not itself practice the patented

invention. See Colleen V. Chien, From Arms Race to Marketplace: The Complex Patent Ecosystem and Its

Implications for the Patent System, 62 HASTINGS L.J. 297, 326–27 (2010) (discussing distinction among various types

of nonpracticing patent entities).

213 USPTO PSM REPORT, supra note 16, at 24–26; BCLT Report, supra note 16, at 596; Gugliuzza, supra note 25, at

652–53.

214 Sarnoff, supra note 113, at 106–24 (reviewing asserted utilitarian and moral benefits of robust Section 101

exclusions); see generally infra “Views on the Purposes of Section 101.”

215 USPTO PSM REPORT, supra note 16, at 27.

216 Id.

217 Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 71 (2012) (quoting Gottschalk v. Benson, 409

U.S. 63, 67 (1972)); Alice Corp. Pty. v. CLS Bank Int’l, 573 U.S. 208, 216 (2014) (“We have described the concern

that drives [the ineligible categories of patentable subject matter] as one of pre-emption.”).

218 Mayo, 566 U.S. at 91.

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prevent patents that reach so broadly that they “threaten downstream innovation” by preempting

all uses of a natural law, abstract idea, or fundamental research tools.219

The preemption rationale is not the only potential justification for Section 101, however.

Although a complete survey of the various rationales proffered for Section 101 is beyond the

scope of this report, at least four broad categories of rationales for Section 101 have been

proposed.220

First, some commentators argue that Section 101’s purpose is to identify certain patents or

categories of patents that should not be granted because their economic harms exceed their

benefits—that is, their net social costs are negative for innovation, or more generally.221

Preemption theory, which claims that certain overbroad patents should be denied patent

protection under Section 101 because of their negative effects on downstream innovation, is an

example from this group.222

Second—in what is in some sense a special case of the first rationale—other commentators assert

that Section 101’s purpose is to identify and deny patents to categories of inventions that would

have been developed even without a patent incentive.223 For example, several commentators have

argued the patents on business methods should be excluded under Section 101 either because they

affirmatively harm innovation and the economy, or because they are simply unnecessary because

sufficient incentives to create business methods would exist even if patents are unavailable.224

Third, some commentators assert that Section 101 (or elements of Section 101 doctrine) are based

not on economic considerations but on moral or ethical concerns.225 For example, the judicial

prohibition on patenting products of nature—such as human DNA sequences—may be motivated

219 See, e.g., Lemley et al., supra note 21, at 1346–47; accord Benson, 409 U.S. at 72 (rejecting patent because it would

“wholly pre-empt the mathematical formula and in practical effect would be a patent on the algorithm itself”). But see

Katherine J. Strandburg, Much Ado About Preemption, 50 HOUS. L. REV. 563, 566 (2012) (critiquing preemption

rationale’s “sole focus on broad downstream impact” as not providing a satisfactory explanation for the Supreme

Court’s Section 101 case law).

220 See generally J. Jonas Anderson, Applying Patent-Eligible Subject Matter Restrictions, 17 VAND. J. ENT. & TECH. L.

267, 269–40, 279–86 (2015) (surveying the “diverse set of proposed theories” of Section 101 and categorizing them

into several broad categories).

221 See Anderson, supra note 220, at 284–85 (overviewing this group of theories); see, e.g., David S. Olson, Taking the

Utilitarian Basis for Patent Law Seriously: The Case for Restricting Patentable Subject Matter, 82 TEMP. L. REV. 181,

184 (2009) (arguing that patentable subject matter doctrine should be driven by looking at when “granting a patent right

for this type of innovation causes more loss to society than gain”).

222 See supra note 219 and accompanying text.

223 See Anderson, supra note 220, at 285–86 (overviewing this group of theories); see, e.g., Pamela Samuelson, Benson

Revisited: The Case Against Patent Protection for Algorithms and Other Computer Program-Related Inventions, 39

EMORY L.J. 1025, 1136 (1990) (arguing that software should not be patentable in part because “the fact that this growth

[in the software industry] has occurred without the aid of patent protection is powerful evidence that patent protection

is not necessary for the software industry to thrive”).

224 See, e.g., Rochelle Cooper Dreyfuss, Are Business Method Patents Bad for Business?, 16 SANTA CLARA COMPUTER

& HIGH TECH. L.J. 263, 274 (2000) (arguing that business method patents are unwise because they “adversely affect

innovation, and worse, the economy”); accord Bilski v. Kappos, 561 U.S. 593, 651 (2010) (Stevens, J., concurring in

the judgment) (arguing that business methods should not be patentable because there are “ample incentives to develop

business methods even without patent protection” (quoting Dan L. Burk & Mark A. Lemley, Policy Levers in Patent

Law, 89 VA. L. REV. 1575, 1618 (2003))).

225 See Anderson, supra note 220, at 286 (overviewing this group of theories); see, e.g., Sarnoff, supra note 113, at 84–

90 (surveying religious and deontological bases for prohibition on patenting science, nature, and ideas); Tun-Jen

Chiang, Competing Visions of Patentable Subject Matter, 82 GEO. WASH. L. REV. 1858, 1860 (2014) (arguing that

Section 101 determinations are “often about noneconomic moral values”).

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by noneconomic, deontological notions of human dignity, or the inviolability of natural

creation.226

Finally, some commentators believe that Section 101 serves no independent purpose in patent law

not already better served by other patentability requirements.227 On this view, Section 101’s

judicially created exceptions to patentable subject matter should simply be eliminated as an

independent requirement for patentability, in favor of a rigorous application of the other

patentability requirements in Sections 102, 103, and 112 of the Patent Act.228

Potential Options for Section 101 Reform

Before examining the particular approaches used in USPTO guidance and proposed legislative

reforms, this section reviews some of the general ways in which Section 101 may or may not be

reformed. These different paths are introduced to contextualize the current Section 101 reform

proposals within the universe of possible reforms. This list is not exhaustive, nor are each of these

options necessarily mutually exclusive.

At a general level, most of the proposed paths forward for Section 101 fall into one of four

categories.229 First, some oppose any legislative intervention, proposing instead to allow the

courts to continue to develop and refine the standards for patent eligibility.230 Second, some

propose replacing the Alice/Mayo framework with an explicit list of subject matter that is patenteligible or -ineligible, similar to the approach that is used for European patents.231 Third, some

propose replacing the Alice/Mayo framework with a different, usually lower, standard for patent

eligibility, such as a requirement that the invention result from human effort, exist outside the

human mind, or contribute to the technological arts.232 Fourth, some propose to do away with any

limitations on patentable subject matter, beyond the four statutory categories and other existing

statutory patentability requirements.233

Continued Common Law Judicial Development

Congress could leave Section 101 as it is, and allow the courts and the USPTO to continue

developing the law of patent-eligible subject matter. Stakeholders and commentators may support

this option for several different reasons. Some may disagree that the Alice/Mayo framework is as

226 Chiang, supra note 225, at 1873–81.

227 See Anderson, supra note 220, at 280 (overviewing this group of theories).

228 See, e.g., Risch, supra note 21, at 591–94 (articulating this view); Davis, supra note 23 (quoting former USPTO

Director David Kappos as calling for abolishing Section 101 and instead “faithfully applying other areas of patent law

to ensure that patents are not obvious or anticipated or lacking in written description”).

229 See David O. Taylor, Amending Patent Eligibility, 50 U.C. DAVIS L. REV. 2149, 2189–2211 (2017) (listing proposed

Section 101 reforms, including a European-style “laundry list” of exclusions, a new “workable eligibility standard,” or

the elimination of the judicially created ineligible categories); USPTO PSM REPORT, supra note 16, at 39–46

(reviewing proposed Section 101 recommendations, including continued judicial and/or administrative development,

codification of explicitly defined Section 101 exceptions, or new standards for patent eligibility); BCLT Report, supra

note 16, at 562–66 (same).

230 See USPTO PSM REPORT, supra note 16, at 39–41; BCLT Report, supra note 16, at 566.

231 See Taylor, supra note 229, at 2198–2201; USPTO PSM REPORT, supra note 16, at 43–45; BCLT Report, supra note

16, at 564.

232 See Taylor, supra note 229, at 2202–06; USPTO PSM REPORT, supra note 16, at 41–43; BCLT Report, supra note

16, at 563–65.

233 See, e.g., Risch, supra note 21, at 591–94; see generally “Requirements for Patentability” (reviewing requirements

for patentability under Sections 102, 103, and 112 of the Patent Act).

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indeterminate or as harmful to innovation as the critics claim.234 Other commentators, even if they

accept the criticisms directed at Alice/Mayo, believe that the courts will eventually refine, clarify,

or otherwise improve the law of patentable subject matter given more time for judicial

development.235 Still other commentators support the current law of Section 101 as affirmatively

good for innovation and society because it precludes property rights in fundamental aspects of

science, nature, and ideas,236 or serves as an important mechanism to weed out overly broad

patents or obtain early dismissal of unmeritorious patent litigation.237

Supporters of continued judicial development may point to the administrative guidance put forth

by the USPTO238 and significant Section 101 decisions of the Federal Circuit239 as promising

steps in the development of Section 101 after the Alice, Mayo, and Myriad decisions. Opponents

of maintaining the legal status quo, for their part, observe that the Supreme Court has not shown

much interest in revisiting its Section 101 jurisprudence despite many opportunities,240 and that

the USPTO and the Federal Circuit are bound by the Court’s decisions.

Specific Statutory List of Included or Excluded Subject Matter Categories

Another potential option would be for Congress to amend Section 101, replacing the Alice/Mayo

framework with a more specific list of subject matter that is patent-eligible or ineligible.

Currently, Section 101 contains a broad list of included subject matter categories (processes,

machines, manufactures, and compositions of matter), and most of the doctrine focuses on the

three judicially created ineligible categories: laws of nature, natural phenomena, and abstract

ideas.241 The “laundry list” approach would seek to make Section 101 clearer and more

predictable by more specifically defining categories of eligible or ineligible subject matter.242

Depending on how this sort of proposal is structured, it would retain the notion of ineligible

classes of subject matter, but define such categories differently, more precisely, and perhaps more

narrowly than the common law exceptions under the Alice/Mayo framework.

The European Patent Convention’s (EPC’s) approach to patent eligibility offers a potential model

for this type of approach.243 Under EPC article 52(1), patent-eligible subject matter reaches “all

234 See BCLT Report, supra note 16, at 566.

235 See USPTO PSM REPORT, supra note 16, at 39.

236 Sarnoff Testimony, supra note 26, at 1.

237 See Patent Eligibility Hearings, supra note 29 (statement of Prof. Paul R. Gugliuzza, Boston University School of

Law), at 1, https://www.judiciary.senate.gov/imo/media/doc/Gugliuzza%20Testimony.pdf [hereinafter Gugliuzza

Testimony] (“[T]he eligibility requirement, though imperfect, plays a crucial role in reducing litigation costs by giving

courts a mechanism to quickly dismiss infringement claims that plainly lack merit.”).

238 See infra “Administrative Developments in the USPTO .”

239 See, e.g., Am. Axle & Mfg. v. Neapco Holdings, 967 F.3d 1285 (Fed. Cir. 2020); Yu v. Apple Inc., 1 F.4th 1040

(Fed. Cir. 2021); Chamberlain Grp., Inc. v. Techtronic Indus. Co., 935 F.3d 1341 (Fed. Cir. 2019); ChargePoint, Inc. v.

SemaConnect, Inc., 920 F.3d 759 (Fed. Cir. 2019); Athena Diagnostics, Inc. v. Mayo Collaborative Servs., LLC, 915

F.3d 743 (Fed. Cir. 2019); Vanda Pharms. Inc. v. West-Ward Pharms. Int’l Ltd., 887 F.3d 1117 (Fed. Cir. 2018); Aatrix

Software v. Green Shades Software, 882 F. 3d 1121 (Fed. Cir. 2018); Berkheimer v. HP Inc., 881 F.3d 1360 (Fed. Cir.

2018); Enfish, LLC v. Microsoft Corp., 822 F.3d 1327 (Fed. Cir. 2016); Finjan, Inc. v. Blue Coat Systems, Inc., 879

F.3d 1299 (Fed. Cir. 2018); McRO, Inc. v. Bandai Namco Games Am. Inc., 837 F.3d 1299 (Fed. Cir. 2016); Bascom

Global Internet Services, Inc. v. AT&T Mobility LLC, 827 F.3d 1341 (Fed. Cir. 2016); Ariosa Diagnostics, Inc. v.

Sequenom, Inc., 788 F.3d 1371 (Fed. Cir. 2015); DDR Holdings, LLC v. Hotels.com, L.P., 773 F.3d 1245 (Fed. Cir.

2014).

240 See infra “Judicial Developments.”

241

See supra “The Law of Section 101.”

242 See Taylor, supra note 229, at 2198, 2200 (coining this term).

243 BCLT Report, supra note 16, at 564.

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fields of technology, provided that they are new, involve an inventive step and are susceptible of

industrial application.”244 At the same time, EPC article 52(2) defines specific subject matter that

is not patentable when claimed “as such”:

(a) discoveries, scientific theories and mathematical methods;

(b) aesthetic creations;

(c) schemes, rules and methods for performing mental acts, playing games or doing

business, and programs for computers;

(d) presentations of information.245

EPC article 53 further denies patents on inventions that are “contrary to [public order] or

morality,” claim “plant and animal varieties,” or claim “methods for treatment of the human or

animal body by surgery or therapy and diagnostic methods practised on the human or animal

body.”246

Assuming that the new statutory categories are more clearly defined than existing judicial

categories, a potential virtue of the laundry-list approach is greater clarity and predictability in the

sort of inventions that are patentable.247 This approach would also more firmly ground subject

matter determinations in the statutory text. On the other hand, the list-of-specific-exclusions

approach might be less flexible and less able to adapt to unforeseen new technologies than other

options.248 It might also, to some degree, replace case-by-case judicial judgments of eligibility

with more categorical legislative ones, which may be a virtue or a vice depending on one’s

perspective.249

Replace Judicial Exceptions with a Different Standard

A third group of proposed Section 101 reforms seeks to replace the Alice/Mayo framework with a

new statutory standard for assessing patent eligibility.250 Proposals in this category are fairly

diverse, but common elements in proposed new standards would limit patent eligibility to

inventions that

•

•

•

result from human effort;251

contribute to the technological arts;252

have practical utility or application;253

244 Convention on the Grant of European Patents art. 52(1), Oct. 5, 1973, 1065 U.N.T.S. 254 (as amended),

https://www.epo.org/law-practice/legal-texts/html/epc/2016/e/EPC_conv_20190401_en_20190326.pdf.

245 Id. art. 52(2)–(3).

246 Id. art. 53.

247 See Taylor, supra note 229, at 2200.

248 See id. at 2201.

249 Compare id. at 2193–97 (arguing that judicial “policymaking” under Section 101 should be constrained), with

Morris, supra note 106, at 107–17 (arguing that a subjective, intuitive, case-by-case, judgment-based approach to

Section 101 is inevitable and “perhaps even desirable”).

250 For examples of this sort of proposal, see Taylor, supra note 229, at 2202–07; USPTO PSM REPORT, supra note 16,

at 42–43, 59–62; BCLT Report, supra note 16, at 563–65.

251 See, e.g., Taylor, supra note 229, at 2202–05; BCLT Report, supra note 16, at 563.

252 See, e.g., USPTO PSM REPORT, supra note 16, at 42, 64.

253 See, e.g., USPTO PSM REPORT, supra note 16, at 43; BCLT Report, supra note 16, at 563–64; Taylor, supra note

229, at 2205–07.

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•

•

cannot be solely performed in the human mind;254

do not preempt all practical uses of a law of nature, abstract idea, or natural

phenomenon.255

Usually, the proposed new patentability standard would supersede the three judicially created

subject matter exclusions and the two-step Alice/Mayo test.256

Several proposed new standards blend more than one of these elements. For example, the

American Intellectual Property Law Association has submitted a Section 101 reform proposal that

replaces the Alice/Mayo framework with a single exception to patent eligibility if an invention

“exists in nature independently of and prior to any human activity” or “is performed solely in the

human mind.”257 A 2017 proposal by the American Bar Association (ABA) would explicitly allow

patenting “practical applications” of laws of nature, natural phenomena, and abstract ideas, so

long as the patent claim does not “preempt the use by others of all practical applications of the

law of nature, natural phenomenon, or abstract idea.”258

It is difficult to generalize given the significant differences among the various proposals in this

category, but stakeholders may wish to consider whether proposed new standards would provide

greater clarity and predictability in patent-eligibility law, while still being flexible enough to

adapt to new technologies.259

Eliminate Implied Patentable Subject Matter Limits

Another option would be for Congress to eliminate the Alice/Mayo framework and judicially

created exceptions to patent eligibility altogether, without replacing them with a new standard or

statutory exceptions.260 Several commentators have argued that patent-eligibility doctrine serves

no purpose that is not already served by the existing statutory patentability requirements of utility,

novelty, obviousness, written description, definiteness, and enablement.261 On this view, the

appropriate course would be for Congress to simply eliminate the nonstatutory eligibility

requirements (i.e., the judicial prohibitions on patenting laws of nature, natural phenomena, and

abstract ideas) in favor of the application of the patentability requirements of Sections 102, 103,

and 112 of the Patent Act.262

Supporters of this approach argue that it advances the policy concerns motivating Section 101

law, but does so in a “more consistent and more rigorous” manner.263 Opponents argue that

254 See, e.g., BCLT Report, supra note 16, at 563.

255 See, e.g., USPTO PSM REPORT, supra note 16, at 60–61.

256 See, e.g., BCLT Report, supra note 16, at 563–65.

257 Am. Intellectual Prop. Law Ass’n, Joint AIPLA-IPO Proposal on Patent Eligibility (May 2018),

https://www.aipla.org/policy-advocacy/legislative/joint-aipla-ipo-proposal-on-patent-eligibility.

258 See USPTO PSM REPORT, supra note 16, at 60.

259 See Taylor, supra note 229, at 2189–97 (articulating general principles for evaluating proposed Section 101

reforms).

260 See BCLT Report, supra note 16, at 565.

261

See Risch, supra note 21, at 594, 606–09; Taylor, supra note 229, at 2171–89.

262 Risch, supra note 21, at 606–09.

263 Id. at 594; accord Taylor, supra note 229, at 2211.

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Section 101 serves important purposes that are distinct from the other patentability requirements,

which would be lost if the judicial exceptions were eliminated.264

Post-Alice Developments in Patent-Eligible Subject

Matter Law and Proposed Reforms

The Supreme Court’s modern patentable subject matter jurisprudence has led to responses from

the courts, the USPTO, and Congress. This section reviews recent judicial, administrative, and

legislative developments on patent-eligible subject matter standards and proposed reforms.

Judicial Developments

Since its 2014 decision in Alice, the Supreme Court has denied dozens of petitions for certiorari

(i.e., requests that the Court hear an appeal) on Section 101 issues, despite calls from some patent

law stakeholders asking the Court to revisit its patent-eligible subject matter jurisprudence.265 For

example, in Sequenom v. Ariosa Diagnostics, Inc.,266 the Supreme Court denied certiorari despite

22 amicus briefs supporting certiorari and calls from commentators, stakeholders, and Federal

Circuit judges urging the Court to take the case to clarify Section 101.267 Similarly, in opinions

concerning rehearing en banc in Athena Diagnostics, Inc. v. Mayo Collaborative Services,268 all

of the active judges on the Federal Circuit called upon the Supreme Court (or Congress) to

change Section 101 law to clearly allow for the patenting of diagnostic methods.269 The Supreme

Court nonetheless denied certiorari in Athena and again declined to revisit its Section 101 case

law.270

Another prominent Section 101 case that the Court declined to hear was American Axle &

Manufacturing v. Neapco Holdings.271 That case was thought by some observers to be an ideal

vehicle for the Court because the patented technology—a method for manufacturing driveline

shafts for automotive vehicles—was tangible and relatively straightforward, yet the lower courts

held it ineligible as directed to a law of nature.272 As in Athena, the Federal Circuit was closely

264 See, e.g., Mayo Collaborative Servs. v. Prometheus Labs., Inc., 566 U.S. 66, 91 (2012) (relying on concerns about

preemption to “decline the Government’s invitation to substitute §§ 102, 103, and 112 inquiries for the better

established inquiry under § 101”); see supra note 210 (citing academic sources); see generally “Views on the Purposes

of Section 101.”

265 See Burman York Mathis III, Supreme Court Denies 43rd Petition for Cert on 101 Grounds in Villena v. Iancu,

IPWATCHDOG (Sept. 3, 2019), https://www.ipwatchdog.com/2019/06/16/supreme-court-denies-43rd-petition-cert-101grounds-villena-v-iancu/id=110425/.

266 See 788 F.3d 1371 (Fed. Cir. 2015), cert. denied, 579 U.S. 928 (2016).

267 BCLT Report, supra note 16, at 577 (describing Sequenom as a “case that many Federal Circuit jurists, scholars, and

practitioners regarded as an ideal vehicle for [the Court to] clarify[] patent eligibility standards”); USPTO PSM Report,

supra note 16, at 11 (same); SCOTUSBLOG, Sequenom, Inc. v. Ariosa Diagnostics, Inc.,

https://www.scotusblog.com/case-files/cases/sequenom-inc-v-ariosa-diagnostics-inc/ (last visited Mar. 31, 2025)

(linking to 22 amicus briefs in support of the petition for certiorari).

268 Athena Diagnostics, Inc. v. Mayo Collaborative Servs., LLC, 915 F.3d 743 (Fed. Cir. 2019), cert. denied, 140 S. Ct.

855 (2020).

269 See Athena Diagnostics, Inc. v. Mayo Collaborative Servs., LLC, 927 F.3d 1333, 1335 (Fed. Cir. 2019) (opinions

regarding the denial of rehearing en banc); CRS Legal Sidebar LSB10344, Judges Urge Congress to Revise What Can

Be Patented, coordinated by Kevin J. Hickey (2020) (reviewing the Federal Circuit’s opinions in Athena Diagnostics).

270

140 S. Ct. 855 (2020).

271 967 F.3d 1285 (Fed. Cir. 2020), cert. denied, 142 S. Ct. 2902 (2022).

272 Id. at 1292–99.

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divided with respect to rehearing American Axle en banc, dividing 6-6, with 5 judges averring

that “[Federal Circuit] rulings on patent eligibility have become so diverse and unpredictable as to

have a serious effect on the innovation incentive in all fields of technology.”273 Many

stakeholders again supported the petition for certiorari in American Axle, including a brief filed

jointly by Senator Tillis, the Hon. Paul R. Michel (a former Chief Judge of the Federal Circuit),

and David J. Kappos (a former USPTO Director).274 The Supreme Court invited the views of the

Solicitor General, who filed a brief supporting a partial grant of certiorari in American Axle.275

The Supreme Court declined to hear the case in 2022.276

In light of the Supreme Court’s apparent reluctance to revisit Section 101, the Federal Circuit has

continued to develop the law of Section 101 within the constraint of the Supreme Court’s

precedents,277 deciding many significant cases applying the Alice/Mayo framework.278 The

Supreme Court’s inaction on Section 101 post-Alice has also led some stakeholders to call for

Congress to intervene on the issue.279

Administrative Developments in the USPTO

The 2019 Revised Patent Subject Matter Eligibility Guidance

In 2019, the USPTO issued Revised Patent Subject Matter Eligibility Guidance (the 2019

Guidance) to assist USPTO patent examiners in determining subject matter eligibility for patent

applications.280 The USPTO noted that the “legal uncertainty” surrounding the Alice/Mayo

framework “poses unique challenges” for the agency, which has thousands of patent examiners

who must make patent-eligibility determinations on hundreds of thousands of applications each

273 Am. Axle & Mfg., Inc. v. Neapco Holdings LLC, 966 F.3d 1347, 1357 (Fed. Cir. 2020) (Newman, J., dissenting

from the denial of rehearing en banc).

274 See Am. Axle & Mfg. v. Neapco Holdings LLC (U.S. No. 20-891), https://www.supremecourt.gov/

search.aspx?filename=/docket/docketfiles/html/public/20-891.html (Supreme Court docket linking to amicus briefs).

275 See Brief for the United States as Amicus Curiae, Am. Axle & Mfg. v. Neapco Holdings LLC, No. 20-891 (U.S.

May 24, 2022), https://www.supremecourt.gov/DocketPDF/20/20-891/226156/20220524150114156_20-891%20%20American%20Axle%20CVSG.pdf.

276 142 S. Ct. 2902 (2022).

277 See, e.g., Athena Diagnostics, Inc. v. Mayo Collaborative Servs., LLC, 927 F.3d 1333, 1337 (Fed. Cir. 2019)

(Hughes, J., concurring in the denial of rehearing en banc) (noting that “we are bound by the Supreme Court[’s]”

precedent even if the result is “problematic” for diagnostic patents in the view of some Federal Circuit judges).

278 See, e.g. Trinity Info Media, LLC v. Covalent, Inc., 72 F.4th 1355 (Fed. Cir. 2023); CardioNet, LLC v. InfoBionic,

Inc, 955 F.3d 1358 (Fed. Cir. 2020); Illumina, Inc. v. Ariosa Diagnostics, Inc., 967 F.3d 1319 (Fed. Cir. 2020); Athena

Diagnostics, Inc. v. Mayo Collaborative Servs., LLC, 915 F.3d 743 (Fed. Cir. 2019); Endo Pharms. Inc. v. Teva

Pharms. USA, Inc., 919 F.3d 1347, 1348 (Fed. Cir. 2019); Cellspin Soft, Inc. v. Fitbit, Inc., 927 F.3d 1306 (Fed. Cir.

2019); Aatrix Software, Inc. v. Green Shades Software, Inc., 882 F.3d 1121 (Fed. Cir. 2018); Berkheimer v. HP Inc.,

881 F.3d 1360, 1363 (Fed. Cir. 2018); Vanda Pharms. Inc. v. W.-Ward Pharms. Int'l Ltd., 887 F.3d 1117 (Fed. Cir.

2018); Enfish, LLC v. Microsoft Corp., 822 F.3d 1327 (Fed. Cir. 2016); McRO, Inc. v. Bandai Namco Games Am.

Inc., 837 F.3d 1299 (Fed. Cir. 2016); Ariosa Diagnostics, Inc. v. Sequenom, Inc., 788 F.3d 1371 (Fed. Cir. 2015); DDR

Holdings, LLC v. Hotels.com, L.P., 773 F.3d 1245 (Fed. Cir. 2014).

279 See infra “Legislative Developments” (reviewing congressional proposals to amend Section 101).

280 Notice, 2019 Revised Patent Subject Matter Eligibility Guidance, 84 Fed. Reg. 50 (Jan. 7, 2019) [hereinafter 2019

Guidance]. USPTO subsequently issued an update to this guidance in October 2019. See U.S. PAT. & TRADEMARK OFF.,

October 2019 Update: Subject Matter Eligibility (Oct. 2019),

https://www.uspto.gov/sites/default/files/documents/peg_oct_2019_update.pdf [hereinafter the October 2019 Update].

These guidance documents have been incorporated in the USPTO’s Manual of Patent Examining Procedure.

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year.281 Accordingly, the USPTO issued revised guidance to its patent examiners to provide “more

clarity and predictability” in their Section 101 determinations.282

The USPTO subsequently incorporated the 2019 Guidance into the Manual of Patent Examining

Procedure (MPEP), which guides USPTO patent examiners in their review of patent

applications.283 The 2019 Guidance made at least two major changes to how patent examiners

evaluate whether a patent application claims patent-ineligible subject matter. First, the Guidance

seeks to provide a clearer definition of what constitutes an ineligible “abstract idea.”284

Previously, examiners would make that determination by comparing the patent claim at issue to

those found to be ineligible “abstract ideas” in previous judicial cases.285 The USPTO found that

this approach had become “impractical” because of an expanding volume of sometimes

contradictory Section 101 case law.286 The 2019 Guidance “distills” the case law into three

categories that examiners will treat as “abstract ideas”:

1) Mathematical concepts—mathematical relationships, mathematical formulas or

equations, mathematical calculations;

2) Certain methods of organizing human activity – fundamental economic principles or

practices (including hedging, insurance, mitigating risk); commercial or legal interactions

(including agreements in the form of contracts; legal obligations; advertising, marketing or

sales activities or behaviors; business relations); managing personal behavior or

relationships or interactions between people (including social activities, teaching, and

following rules or instructions); and

3) Mental processes – concepts performed in the human mind (including an observation,

evaluation, judgment, opinion).287

Under the Guidance, patent claims that do not recite matter that falls into one of these three

groupings should not be treated as an “abstract idea” except in “rare circumstance[s].”288

Second, the 2019 Guidance clarifies when examiners will treat a patent claim as “directed to” an

ineligible category (abstract ideas, laws of nature, or natural phenomena) under step one of the

Alice/Mayo test.289 In particular, the USPTO will not treat a claim as “directed to” an ineligible

concept if “the claim as a whole integrates the recited judicial exception into a practical

application of the exception.”290 If the claim does integrate a practical application—such as

281 See 2019 Guidance, supra note 280, at 50 (“The legal uncertainty surrounding Section 101 poses unique challenges

for the USPTO, which must ensure that its more than 8500 patent examiners and administrative patent judges apply the

Alice/Mayo test in a manner that produces reasonably consistent and predictable results across applications, art units

and technology fields.”); see also U.S. PAT. & TRADEMARK OFF., U.S. Patent Statistics Chart Calendar Years 1963–

2015, https://www.uspto.gov/web/offices/ac/ido/oeip/taf/us_stat.htm (last visited Mar. 5, 2025) (indicating that the

USPTO received 589,410 applications in 2015).

282 See 2019 Guidance, note 280, at 50.

283 See U.S. PATENT & TRADEMARK OFF., Subject Matter Eligibility, https://www.uspto.gov/patents/laws/examinationpolicy/subject-matter-eligibility (last visited Mar. 6, 2025); U.S. PAT. & TRADEMARK OFF., MANUAL OF PATENT

EXAMINING PROCEDURE §§ 2103–2106 (last revised Jan. 2024), available at

https://www.uspto.gov/web/offices/pac/mpep/index.html [hereinafter MPEP].

284 Id. at § 2106.04(a).

285 2019 Guidance, note 280, at 51.

286 Id. at 52.

287 MPEP § 2106.04(a) (internal cross-references omitted).

288 Id.

289 Id. at § 2106.04. The USPTO calls the Alice/Mayo test’s first step “Step 2A” of its Section 101 examination process.

See id.

290 Id. at § 2106.04(d) (emphasis added).

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improving the functioning of a computer, effecting a particular treatment for a disease, or

implementing the exception into a particular machine or manufacture—then the USPTO will treat

the claim as patent-eligible, without having to examine the patent application for an “inventive

concept” under step two of the Alice/Mayo framework.291

The 2019 Guidance was generally perceived as lowering Section 101 barriers to patentability,

especially for computer-related inventions.292 Some commentators praised the Guidance for

providing greater clarity to patent examiners, while other stakeholders criticized the Guidance as

inconsistent with the Supreme Court’s Section 101 decisions.293

Although the USPTO’s 2019 Guidance changes how USPTO examiners review new patent

applications, the Guidance is not binding on the courts when patents are challenged in litigation

(unlike decisions of appellate courts or statutes). The USPTO lacks general substantive

rulemaking authority,294 and the Guidance itself states that it is only a “tool for internal USPTO

management” that lacks “the force and effect of law.”295 Although the Federal Circuit has issued

somewhat contradictory signals on this point,296 courts would only follow the Guidance if they

found its reasoning to be persuasive and agreed that it was the “best reading” of Section 101.297

291 Id. at §§ 2106, 2106.04(d).

292 See, e.g., James J. DeCarlo & George David Zalpea, The USPTO’s New § 101 Guidance: Progress or Pitfall?, N.J.

LAW J. (May 13, 2019), https://www.gtlaw.com/en/insights/2019/5/published-articles/the-usptos-new-101-guidanceprogress-or-pitfall (“In practice, many applicants are seeing a noticeable decrease of rejections under § 101 [after the

2019 Guidance.]”); Michelle Holoubeck & Lestin Kenton, 5 Things to Know About USPTO’s New Eligibility

Guidance, LAW360 (Jan. 8, 2019), https://www.law360.com/articles/1116262/5-things-to-know-about-uspto-s-neweligibility-guidance (“The [PTO’s] new guidance eases the burden on patenting computer-implemented invention.”).

293 See generally Stuart P. Meyer, No Shortage of Viewpoints on New USPTO Eligibility Guidelines, BILSKI BLOG

(Mar. 26, 2019), https://www.fenwick.com/bilski-blog/no-shortage-of-viewpoints-on-new-uspto-patent-eligibilityguidelines (reviewing comments received by USPTO on the 2019 Guidance and noting that “both the ‘new Guidance is

great’ and the ‘new Guidance doesn’t follow Alice’ camps are very well represented”).

294 Merck & Co. v. Kessler, 80 F.3d 1543, 1549–50 (Fed. Cir. 1996) (holding that while the USPTO may promulgate

regulations directed to the conduct of its own proceedings, it lacks authority to “issue substantive rules” under the

Patent Act); Ass’n for Molecular Pathology v. USPTO, 689 F.3d 1303, 1357 (Fed. Cir. 2012) (Bryson, J., concurring in

part and dissenting in part) (“As we have recognized, the PTO lacks substantive rulemaking authority as to issues such

as patentability.”); see generally Melissa F. Wasserman, The Changing Guard of Patent Law: Chevron Deference for

the PTO, 54 WM. & MARY L. REV. 1959, 1962 (2013) (“[The USPTO] lacks robust substantive rule-making authority

and receives no judicial deference for its legal interpretations of the Patent Act.”).

295 2019 Guidance, supra note 280, at 51.

296 Compare Nat. Alternatives Int’l, Inc. v. Creative Compounds, LLC, 918 F.3d 1338, 1346 n.2 (Fed. Cir. 2019)

(noting that “[t]he parties dispute the persuasiveness of this document and the weight we should afford it under

[Skidmore],” but declining to decide whether the 2019 Guidance should receive any deference), with Cleveland Clinic

Found. v. True Health Diagnostics LLC, 760 F. App’x 1013, 1020 (Fed. Cir. 2019) (“While we greatly respect the

PTO’s expertise on all matters relating to patentability, including patent eligibility, we are not bound by its guidance.”).

See generally Andrew Michaels, How Much Deference Courts Owe to USPTO Guidance, LAW360 (June 20, 2019),

https://www.law360.com/ip/articles/1171217/how-much-deference-courts-owe-to-uspto-guidance.

297 See Loper Bright Enters. v. Raimondo, No. 22-451, slip op. at 23 (U.S. June 28, 2024); United States v. Mead Corp.,

533 U.S. 218, 234 (2001) (“[A]n agency’s interpretation [of a statute] may merit some deference whatever its form,

given the specialized experience and broader investigations and information available to the agency, and given the

value of uniformity in its administrative and judicial understandings of what a national law requires.”) (citations

omitted); Skidmore v. Swift & Co., 323 U.S. 134, 140 (1944) (“The weight of [an informal agency] judgment in a

particular case will depend upon the thoroughness evident in its consideration, the validity of its reasoning, its

consistency with earlier and later pronouncements, and all those factors which give it power to persuade, if lacking

power to control.”).

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Following the 2019 Guidance, the USPTO has continued efforts to increase clarity and

consistency in its Section 101 determinations.298 In 2020, the USPTO Office of the Chief

Economist issued a report on patent examination outcomes following Alice.299 That study found

that while Section 101 rejections in certain technological fields increased by 31% in the 18

months after Alice, the rejection rate decreased by 35% after issuance of the 2019 Guidance, with

less variability in outcomes across examiners.300 In response to a 2021 letter from Senators Tillis

and Cotton,301 the USPTO launched the Deferred Subject Matter Eligibility Response Pilot

Program, which invites selected patent applicants to defer consideration of subject-matter

eligibility issues until other patentability issues (such as those under Sections 102, 103, and 112)

are resolved.302

2022 USPTO Report on Stakeholder Views

In 2022, at the urging of a group of Senators,303 the USPTO solicited public comment and

published a report for Congress summarizing stakeholder views on current patent-eligible subject

matter law.304 While the report found a consensus that patent-eligibility law should be “clear,

predictable, and consistently applied,” stakeholders differed on whether current Section 101 law

achieved that ideal.305 Finding a “continuing divide” on the issue, the USPTO report indicated

that defenders of the Alice/Mayo framework (primarily from the computer technology industry)

found current law to be sufficiently clear and an important tool for addressing overbroad patents

and abusive lawsuits.306 On the other side, critics of the Alice/Mayo framework (especially lifescience industries) found the current law to be unpredictable and to have detrimental effects on

innovation and investment in the development of new technologies.307

2024 Artificial Intelligence Eligibility Guidance

Patent applications relating to artificial intelligence (AI) technologies doubled between 2002 and

2018.308 Some stakeholders worry that patents on AI inventions are at risk under the Alice/Mayo

298 See generally Kathy Vidal, Providing Clear Guidance on Patent Subject Matter Eligibility, U.S. PAT. &

TRADEMARK OFF. (July 25, 2022), https://www.uspto.gov/blog/director/entry/providing-clear-guidance-on-patent.

299 ANDREW A. TOOLE & NICHOLAS A. PAIROLERO, ADJUSTING TO ALICE (U.S. Pat. & Trademark Off. April 2020),

https://www.uspto.gov/sites/default/files/documents/OCE-DH_AdjustingtoAlice.pdf.

300 Id. at 1.

301 Letter from Sens. Thom Tillis and Tom Cotton to Drew Hirschfeld (Mar. 22, 2021),

https://www.uspto.gov/sites/default/files/documents/sens-sequencedexam-20210322.pdf.

302 USPTO, Deferred Subject Matter Eligibility Response Pilot Program, 87 Fed. Reg. 776 (Jan. 6, 2022). This pilot

program is “designed to evaluate how deferred applicant responses to subject matter eligibility (SME) rejections affect

examination efficiency and patent quality.” U.S. PAT. & TRADEMARK OFFICE, Deferred Subject Matter Eligibility

Response (DSMER) Pilot Program, https://www.uspto.gov/patents/initiatives/patent-application-initiatives/deferredsubject-matter-eligibility-response (last visited Mar. 31, 2025).

303 See Letter from Sens. Thom Tillis, Mazie Hirono, Tom Cotton and Christopher Coons to Drew Hirschfeld (Mar. 5,

2021), https://www.tillis.senate.gov/services/files/04D9DCF2-B699-41AC-BE62-9DCA9460EDDA.

304 U.S. PAT. & TRADEMARK OFF., PATENT ELIGIBLE SUBJECT MATTER: PUBLIC VIEWS ON THE CURRENT JURISPRUDENCE

IN THE UNITED STATES (June 2022), https://www.uspto.gov/sites/default/files/documents/USPTOSubjectMatterEligibility-PublicViews.pdf [hereinafter 2022 PUBLIC VIEWS REPORT].

305 Id. at ii, 41.

306 Id. at 41.

307 Id.

308 See USTPO, Off. of the Chief Economist, Inventing AI: Tracing the Diffusion of Artificial Intelligence with U.S.

Patents (Oct. 2020), at 3, https://www.uspto.gov/sites/default/files/documents/OCE-DH-AI.pdf.

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framework because they might be characterized as claiming abstract ideas.309 In 2024, USPTO

issued updated guidance on patent eligibility focusing on AI-related inventions.310

USPTO’s 2024 AI Eligibility Guidance supplements its general 2019 Guidance on patent-eligible

subject matter. As explained above, under the 2019 Guidance, claims are eligible under

Alice/Mayo step one if the claim either (1) does not “recite” a judicial exception, or (2) has

additional elements that “integrate” the judicial exception into a practical application of ineligible

subject matter.311 The 2024 AI Eligibility Guidance focuses on this step, giving several examples

designed to illustrate when claims on AI inventions recite or “merely involve” abstract ideas, and

when claims integrate an abstract idea into a practical application by improving the functioning of

a computer or another technology.312

As an example, the 2024 AI Eligibility Guidance explains that a claim on an application-specific

integrated circuit for an artificial neural network comprising synaptic circuits, a microprocessor,

and an array of organized “neurons” is patent-eligible because it is directed to specific hardware

components and thus does not recite an abstract idea.313 By contrast, a general method of using a

deep neural network to analyze a speech sample with multiple sources is ineligible because it

claims a mathematical process.314 However, a specific method of using a deep neural network to

separate a mixed speech sample, generate separate waveforms for each speech source, and

recombine them into a new mixed sample without unwanted sources is eligible as a practical

application of an abstract idea.315

While some stakeholders appreciated USPTO’s efforts to provide more guidance on how

examiners will approach patent eligibility issues for AI-related inventions,316 others asserted that

the 2024 AI Eligibility Guidance should have done more to clarify the application of the

Alice/Mayo framework for such inventions.317

309 See 2022 PUBLIC VIEWS REPORT, supra note 304, at 8.

310 USPTO, 2024 Guidance Update on Patent Subject Matter Eligibility, Including on Artificial Intelligence, 89 Fed.

Reg. 58,128 (July 17, 2024) [hereinafter 2024 AI Eligibility Guidance]. Another CRS product reviews USPTO’s 2024

AI Eligibility Guidance in more detail. See generally CRS Legal Sidebar LSB11251, Artificial Intelligence and Patent

Law, by Kevin J. Hickey and Christopher T. Zirpoli (2024).

311 See MPEP § 2106.05

312 2024 AI Eligibility Guidance, 89 Fed. Reg. at 58,134–38.

313 See USPTO, July 2024 Subject Matter Eligibility Examples,

https://www.uspto.gov/sites/default/files/documents/2024-AI-SMEUpdateExamples47-49.pdf (last visited Mar. 11,

2025), at 5.

314 Id. at 18–21.

315 Id. at 21–24.

316 See, e.g., PhRMA, Comments of the Pharmaceutical Research and Manufacturers of America in Response to the

USPTO’s 2024 Guidance Update on Patent Subject Matter Eligibility, Including on Artificial Intelligence (Oct. 16,

2024), https://www.regulations.gov/comment/PTO-P-2024-0026-0018 (“PhRMA appreciates USPTO’s efforts to

streamline interpretation of [patent-eligible subject matter] jurisprudence and application to pending matters before the

Office so as to create a more predictable landscape for patent applicant.”).

317 See, e.g., Eileen McDermott & Steve Brachmann, IP Organizations Want More on USPTO’s AI Patent Eligibility

Guidance, IPWATCHDOG, https://ipwatchdog.com/2024/10/20/ip-organizations-want-usptos-ai-patent-eligibilityguidance/id=182378/ (Oct. 20, 2024) (summarizing public comments on the 2024 AI Eligibility Guidance).

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Legislative Developments

The 116th Congress

The 116th Congress saw one formal proposal to reform Section 101 introduced in the House. In

the Senate, the Chairman and Ranking Member of the Subcommittee on Intellectual Property of

the U.S. Senate Committee on the Judiciary held a series of hearings on Section 101 issues and

circulated several informal draft proposals to amend Section 101. Ultimately, these Members did

not introduce formal legislation in the 116th Congress.

The Restoring America’s Leadership in Innovation Act of 2020

In the House, Representative Massie introduced H.R. 7366, the Restoring America’s Leadership

in Innovation Act of 2020 (RALIA 2020).318 Alongside provisions designed to reverse many of

the changes in patent law enacted through the 2011 America Invents Act,319 Section 7 of RALIA

2020 would have responded to the Supreme Court’s Section 101 decisions. Expressing the view

that the Court’s recent Section 101 jurisprudence “has harmed the progress of science and the

useful arts,” RALIA 2020 would have “effectively abrogate[d]” those decisions (specifically,

Alice “and [its] predecessors”).320

To “ensure that life sciences discoveries, computer software, and similar inventions and

discoveries are patentable,” RALIA 2020 would have replaced the three judicially created

exceptions to patent-eligible subject matter with a single narrow statutory exception.321 Under

RALIA 2020, any new and useful process, machine, manufacture, or composition of matter

would have been patent-eligible unless “the claimed invention as a whole, as understood by a

person having ordinary skill in the art, exists in nature independently of and prior to any human

activity, or exists solely in the human mind.”322 RALIA 2020 would have thus expanded the types

of inventions that are patentable compared to the status quo under Alice/Mayo. RALIA 2020

would have also established that eligibility determinations under Section 101 shall be made

“without regard as to the requirements or conditions of sections 102, 103, and 112 of this title, or

the claimed invention’s inventive concept.”323 This provision would have sought to separate

eligibility questions under Section 101 from issues of novelty, nonobviousness, enablement, and

disclosure more specifically addressed in other provisions of the Patent Act.

The First Tillis-Coons Proposal

In April 2019, Senators Tillis and Coons—joined by Representatives Collins (GA), Johnson

(GA), and Stivers—released a framework for legislative Section 101 reform (the First TillisCoons Proposal).324 The framework’s release followed multiple roundtables with patent law

318 H.R. 5874, 117th Cong. (2021).

319 See, e.g., id. §§ 4–5 (abolishing the PTAB and the IPR/PGR procedures).

320 Id. § 7(b).

321 Id. § 7(a).

322 Id.

323 Id.

324 See Press Release, Office of Sen. Thom Tillis, Sens. Tillis and Coons and Reps. Collins, Johnson, and Stivers

Release Section 101 Patent Reform Framework (Apr. 17, 2019), https://www.tillis.senate.gov/2019/4/sens-tillis-andcoons-and-reps-collins-johnson-and-stivers-release-section-101-patent-reform-framework [hereinafter Sen. Tillis April

17 Press Release]; Sen. Tillis et al., Draft Outline for Section 101 Reform,

(continued...)

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stakeholders on Section 101 and the effect of the Alice/Mayo framework on, for example,

innovation in artificial intelligence, medical diagnostics, and personalized medicine.325

The First Tillis-Coons Proposal would have retained the four current statutory categories of

patentable inventions, but removed the requirement that the invention or discovery be “new and

useful” from Section 101.326 Patent eligibility would have instead been determined “by

considering each and every element of the claim as a whole and without regard for considerations

properly addressed by [Sections] 102, 103 and 112 [of the Patent Act].”327

In place of the judicially created exceptions to patent eligibility, which the First Tillis-Coons

Proposal would have abrogated by statute, the proposal listed five “exclusive” categories of

patent-ineligible subject matter: (1) fundamental scientific principles; (2) products that exist

solely and exclusively in nature; (3) pure mathematical formulas; (4) economic or commercial

principles; and (5) mental activities.

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