Amicus Curiae Brief — Gilbert P. Hyatt, Petitioner v. John A. Squires, Under Secretary of Commerce for Intellectual Property and Director, United States Patent and Trademark Office

Supreme Court briefApr 6, 2026

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No. 25-1049

In the

Supreme Court of the United States

____________________

GILBERT P. HYATT,

Petitioner,

JOHN A. SQUIRES, UNDER SECRETARY OF COMMERCE FOR

INTELLECTUAL PROPERTY AND DIRECTOR OF THE UNITED

STATES PATENT AND TRADEMARK OFFICE,

Respondent.

On Petition for Writ of Certiorari to the United

States Court of Appeals for the Federal Circuit

BRIEF OF AMICUS CURIAE DR. RON D. KATZNELSON

IN SUPPORT OF PETITIONER

CHARLES E. MILLER

ASSOCIATION OF AMICUS COUNSEL

411 MAIN STREET #404

STONEHAM, MA 02180-3595

Tel.: (516) 641-3378

charles.miller@cmilleriplaw.com

Counsel of Record

April 3, 2026

TABLE OF CONTENTS

Page

TABLE OF CONTENTS ..............................................i

TABLE OF AUTHORITIES ....................................... ii

INTEREST OF AMICUS CURIAE ........................... 1

SUMMARY OF ARGUMENT ..................................... 2

ARGUMENT ............................................................... 4

I. Introduction............................................................ 4

II. Congress prescribed by statute all possible

modes of forfeiture or loss of patent rights

and excluded prosecution laches ........................... 6

III.The doctrine of prosecution laches

contravenes the “shall have the same

effect” clause of § 120 ........................................... 10

IV. Congress knows when to make equitable

doctrines available ............................................... 12

V. The Patent Act’s framework specifically

facilitates prosecuting continuing

applications over many years .............................. 18

V.A The American “Prospecting Patent

Bargain” for disclosing improvements in

Continuation-In-Part applications over

“widely divergent times” ................................ 21

CONCLUSION .......................................................... 26

TABLE OF AUTHORITIES

Pages

CASES

Almendarez-Torres v. United States, 523 US

224 (1998) ...............................................................8

Barnhart v. Peabody Coal Co., 537 U.S. 149

(2003) ................................................................ 9, 11

Custis v. United States, 511 U.S. 485, 492

(1994) ....................................................................17

Helsinn Healthcare S.A. v. Teva

Pharmaceuticals USA, Inc., 139 S. Ct. 628

(2019) ................................................................ 9, 24

Hilton Davis Chemical Co. v. WarnerJenkinson Co., Inc., 62 F. 3d 1512 (Fed.

Cir. 1995) ..............................................................23

Hyatt v. Hirshfeld, 998 F. 3d 1347 (Fed. Cir.

2021) .......................................................................5

Hyatt v. Stewart, 148 F. 4th 1376 (Fed. Cir.

2025) .......................................................................5

Immersion Corp. v. HTC Corp., 826 F.3d 1357

(Fed. Cir. 2016) ....................................................20

In re Bogese, 303 F. 3d 1362 (Fed. Cir. 2002). ............5

In re Gibbs, 437 F.2d 486 (CCPA 1971)....................10

In re Henriksen, 399 F.2d 253 (CCPA 1968) ............20

In re Hogan, 559 F.2d 595 (CCPA 1977) ..................12

In re Sarett, 327 F.2d 1005 (CCPA 1964).................19

Metallizing Engineering Co. v. Kenyon Bearing

& AP Co., 153 F. 2d 516 (2nd Cir. 1946) ......... 9, 24

iii

Raleigh & Gaston R. Co. v. Reid, 80 US 269

(1872) ......................................................................9

Scott Paper Co. v. Marcalus Mfg. Co., 326 U.S.

249 (1945) .............................................................22

Symbol Techs., Inc. v. Lemelson Med., 277

F.3d 1361 (Fed. Cir. 2002) .....................................4

Symbol Techs., Inc. v. Lemelson Med., 422

F.3d 1378 (Fed. Cir. 2005) ...................................19

United States v. Johnson, 529 US 53 (2000) ..............8

Whitman v. American Trucking Assns., Inc.,

531 US 457 (2001) ................................................16

STATUTES

15 U.S.C. § 1064(3) .............................................. 14, 15

15 U.S.C. § 1064(5) ....................................................15

15 U.S.C. § 1069 ............................................ 12, 15, 16

15 U.S.C. § 1115(b)(9) ......................................... 12, 15

15 U.S.C. § 1116(a) ....................................................13

15 U.S.C. § 1117(a) .............................................. 13, 15

15 U.S.C. § 1127 ........................................................14

15 U.S.C. §§ 1052 ......................................................15

35 U.S.C. § 101 ................................................ 6, 19, 21

35 U.S.C. § 102 ...................................... 6, 8, 13, 14, 24

35 U.S.C. § 102(b) .................................................. 9, 24

35 U.S.C. § 102(c) .................................................. 9, 10

35 U.S.C. § 102(g) ........................................................9

35 U.S.C. § 112 .................................................... 21, 22

35 U.S.C. § 120 .................................. 10, 11, 12, 19, 22

35 U.S.C. § 121 ..........................................................19

35 U.S.C. § 131 ............................................................6

35 U.S.C. § 133 ..........................................................13

35 U.S.C. § 135 ..........................................................13

35 U.S.C. § 145 ............................................................5

35 U.S.C. § 154 .................................................... 13, 14

35 U.S.C. § 286 .................................................... 13, 14

PUBLIC LAWS, STATUTES AT LARGE

Patent Act, Pub. L. 82-593, 66 Stat. 792

(July 19, 1952) ................ 4, 6, 10, 13, 16, 18, 21, 24

Special Act of March 2, 1901, 56th Cong. 2nd

Sess., 31 Stat. 1788. Ch. 821. ..............................17

Trademark Act, Pub.L. 79-489, 60 Stat. 427

(July 5, 1946) ...................................... 12, 14, 17, 18

RULES

Supreme Court Rule 37.2 ............................................1

Supreme Court Rule 37.6 ............................................1

OTHER AUTHORITIES

Antonin Scalia and Bryan A. Garner, Reading

Law: The Interpretation of Legal Texts

(Thomson/West 2012) ................................ 9, 11, 22

Cesare Righi, et al, “Continuing patent

applications at the USPTO,” 52 Research

Policy, 104742 (2023) ...........................................20

Donald S. Chisum, “Best Mode Concealment

and Inequitable Conduct in Patent

Procurement,” 13 Santa Clara Computer &

High Tech. L. J. 277, 282 (1997) ......................... 25

MPEP § 201 (1949) ....................................................18

PTO, “Studying Applications with Large

Patent Families,” (June 2025) (Slide 8). .............21

Ron D. Katznelson, “Patent Continuations,

Product Lifecycle Contraction and the

Patent Scope Erosion.” Southern California

Law Associations Intellectual Property

Spring Seminar, (June 8-10, 2007). ......................2

Senate Rep. 82-1979, “Revision of Title 35,

United States Code,” (June 27, 1952) .................20

INTEREST OF AMICUS CURIAE 1

Amicus curiae Ron D. Katznelson, Ph.D., is a

technology entrepreneur, named inventor on 25 U.S.

patents and applications and an independent scholar

of the patent system. He is the author of several

amicus briefs on patent matters, filed with the U.S.

Supreme Court and the Court of Appeals for the

Federal Circuit. He served as the Chairman of the

Intellectual Property Committee of IEEE-USA

during 2019 and 2020 and advises high technology

startup companies since 2005.

Dr. Katznelson’s interest in this case is

twofold. First, he has used continuing application

practice in his own patent applications at the U.S.

Patent and Trademark Office (“PTO”) and

experienced the critical role of patents issued from

such applications in appropriating returns from

patented inventions. Second, he conducted and

published empirical research on continuing

application practice, showing how their share

increased over time, including documenting a trend

of narrowing patent claim scope. 2 Dr. Katznelson’s

1 Pursuant to Supreme Court Rule 37.6, counsel for the amicus

curiae certifies that he fully reviewed this brief that was

authored by amicus curiae and that no party or counsel for any

party authored this brief in whole or in part and that no person

or entity other than the amicus made a monetary contribution

intended to fund the preparation or submission of the brief.

Rule 37.2 notice of the intent to file this brief was timely

provided by email to counsel of record for Petitioner and for

Respondent.

2 Ron D. Katznelson, “Patent Continuations, Product Lifecycle

Contraction and the Patent Scope Erosion - A New Insight into

-2detailed study and experience in the filed as

particularly expressed in this brief should be helpful

in aiding this Court on the decision to grant

certiorari.

SUMMARY OF ARGUMENT

The Question Presented in this case is

“Whether the PTO may invoke the equitable doctrine

of prosecution laches to deny a patent to an

applicant who has complied with all the Patent Act's

timeliness provisions.” The answer is categorically

and unconditionally “No”, which applies in any

tribunal, and the reason for that lies within the plain

statutory text. Congress established in the Patent

Act a closed and comprehensive statutory framework

governing both entitlement to a patent and the

circumstances under which that entitlement may be

lost. The Act specifies the exclusive conditions for

patentability and expressly enumerates the

circumstances that result in forfeiture or loss of the

patent right. By defining those conditions in detail,

Congress foreclosed on any additional, judge-made

grounds for forfeiture based on equitable

assessments of prosecution delay. Allowing

prosecution laches to extinguish patent rights

despite compliance with statutory requirements

improperly converts a statutory entitlement to a

patent into a discretionary privilege conflicting with

the law.

The

same

statutory

design

governs

continuation practice. Section 120 guarantees that a

Patenting Trends.” Southern California Law Associations

Intellectual Property Spring Seminar, (June 8-10, 2007).

Available at SSRN: https://ssrn.com/abstract=1001508.

-3continuing application meeting its exhaustive

enumerated conditions “shall have the same effect” as

though filed on the date of the earlier parent

application. Invoking prosecution laches to deny

enforceability of such applications nullifies that

statutory guarantee by imposing extra-statutory

timing requirements Congress deliberately omitted.

The Patent Act instead facilitates prosecution of

continuing applications over extended periods,

recognizing that divisional, continuation, and

continuation-in-part filings commonly occur across

many years as inventions are refined, developed, and

commercialized. These practices are not anomalies

but central features of the statutory scheme, and

Congress expected chains of related applications to

mature at widely divergent times while retaining the

benefit of earlier disclosure dates.

Congress also demonstrated that when it

intends equitable doctrines to govern timeliness, it

says so expressly. The Lanham Act explicitly

authorizes courts and the PTO to apply equitable

doctrines such as laches, whereas the Patent Act

contains no comparable authorization and instead

prescribes specific statutory timing rules and

consequences. This contrast reflects deliberate

legislative design: trademark law leaves timing

issues to equity, while patent law resolves them

through statute. The Federal Circuit’s application of

prosecution laches disregards that distinction and

inserts equity where Congress provided a

comprehensive statutory regime.

Finally, the statutory continuation framework

reflects the unique American “prospecting patent

bargain,” which encourages early continuous

disclosure of inventions’ “best mode” in exchange for

-4allowing

inventors

continue

developing

improvements and disclosing better implementations

over time through continuation-in-part applications

while preserving early priority dates. These

developments frequently span many years and are

expressly accommodated by the Patent Act. Treating

such extended prosecution as presumptively

inequitable undermines Congress’s chosen balance

between early disclosure and continued technological

refinement. Because the Federal Circuit’s decisions

permit equitable forfeiture of patent rights contrary

to this statutory structure, this Court should grant

certiorari to clarify that prosecution laches has no

place within the Patent Act’s closed and

comprehensive framework. This brief takes no

position on the patentability or the prosecution at

the PTO of Petitioner’s underlying patent

applications.

ARGUMENT

I. Introduction

Through two influential decisions in 2002 that

marked a stark departure from judicial holdings

since the 1952 Patent Act, the Federal Circuit

substituted the patent statutes with judge-made law,

to extinguish patent rights via equitable powers of

prosecution laches never provided by Congress,

under the extra-statutory charge of applicant’s

“unreasonable

and

unexplained

delay

prosecution.” The first decision in Symbol

Technologies 3 empowered courts under that charge

3 Symbol Techs., Inc. v. Lemelson Med., 277 F.3d 1361 (Fed.

Cir. 2002) (“Symbol I”).

-5to hold unenforceable patents in infringement suits

and the second decision, In re Bogese, 4 empowered

the PTO to do so through prosecution laches

rejection of pending applications. In its decisions

below in Hyatt I5 and Hyatt II,6 the Federal Circuit

expanded the reach of the prosecution laches

doctrine to proceedings under 35 U.S.C. § 145, and

for the first time created a substantive burdenshifting rule holding that “a delay of more than six

years raises a ‘presumption that it is unreasonable,

inexcusable, and prejudicial.’”7

This brief shows that these decisions

contravene the patent statute. Leaving them stand

threaten

any

patent

applicant

prosecuting

continuing applications at the PTO over extended

period after the original priority date with the risk of

patent rights forfeiture. That burden-shifting risk

arises presumptively any time a third party can

merely allege that the applicant’s prosecution

involved “unreasonable and unexplained” delay,

even though the applicant complied with all

statutory and regulatory timeliness requirements.

Patent application prosecution from priority filing to

patent issuance including through continuing

applications involves objective and necessary

durations spanning many years. A statistical study

reported by the Small Business Technology Council

4 In re Bogese, 303 F. 3d 1362 (Fed. Cir. 2002).

5 Hyatt v. Hirshfeld, 998 F. 3d 1347 (Fed. Cir. 2021) (“Hyatt

I”).

6 Hyatt v. Stewart, 148 F. 4th 1376 (Fed. Cir. 2025) (“Hyatt II”).

7 Hyatt I, 998 F. 3d at 1369. (emphasis added).

-6(“SBTC”) 8 shows that 30% of US patents can be

subject to such prosecution laches allegation based

on the presumptions created by the CAFC in the

Hyatt decisions.

It is argued that regardless of prosecution time

durations, the judge-made equitable doctrine of

prosecution laches cannot be sustained under the

Patent Act and Supreme Court controlling

precedents. All prosecution timeliness requirements

were set by Congress in statute; the statute itself

provides the exclusive modes for applicants’

forfeiture of their patent rights; and Congress left no

room for equitable judgements on those conditions.

II. Congress prescribed by statute all

possible modes of forfeiture or loss of

patent rights and excluded prosecution

laches

The 1952 Patent Act 9 provided in 35 U.S.C.

§ 101 that obtaining a patent is “subject to the

conditions and requirements of this title”) (emphasis

added). When those statutory conditions and

requirements are met, the applicant is “entitled to a

patent,” and the PTO “shall issue a patent therefor.”

35 U.S.C. § 131 (emphasis added). Upon enactment

in 1952, 35 U.S.C. § 102 provided the following:

(emphasis added below)

8 “Br. of SBTC in Support of Rehearing, (November 13, 2025)

(See

Addendum

https://sbtc.org/wpcontent/uploads/2025/11/SBTC-CAFC-Submission-AmicusBrief-Hyatt-Nov-13-2025-Stamped.pdf#page=33).

9 Pub. L. 82-593, 66 Stat. 792 (July 19, 1952) (Hereinafter the

“Patent Act”)

-7Conditions for patentability; novelty and

loss of right to patent

A person shall be entitled to a patent unless—

(a) the invention was known or used by others

in this country, or patented or described in a

printed publication in this or a foreign country,

before the invention thereof by the applicant for

patent, or

(b) the invention was patented or described in a

printed publication in this or a foreign country

or in public use or on sale in this country, more

than one year prior to the date of the

application for patent in the United States, or

(d) the invention was first patented or caused to

be patented by the applicant or his legal

representatives or assigns in a foreign country

prior to the date of the application for patent in

this country on an application filed more than

twelve months before the filing of the

application in the United States, or

(e) the invention was described in a patent

granted on an application for patent by another

filed in the United States before the invention

thereof by the applicant for patent, or

(f) he did not himself invent the subject matter

sought to be patented, or

(g) before the applicant's invention thereof the

invention was made in this country by another

who had not abandoned, suppressed, or

concealed it. In determining priority of

-8invention there shall be considered not only the

respective dates of conception and reduction to

practice of the invention, but also the

reasonable diligence of one who was first to

conceive and last to reduce to practice, from a

time prior to conception by the other.

Here, Congress enumerated a series of

disjunctive exceptions and conditions under the

section heading including “loss of right to patent,”

which are enforced both during prosecution of an

application at the PTO and after a patent is issued.

It is well-recognized that “the title of a statute and

the heading of a section are tools available for the

resolution of a doubt about the meaning of a

statute.” 10 There can be little doubt that the

enumerated exceptions and conditions under this

heading specify in detail all the possible modalities

for the “loss of right to patent,” and that those are

exhaustive. “When Congress provides exceptions in a

statute, it does not follow that courts have authority

to create others. The proper inference, and the one

we adopt here, is that Congress considered the issue

of exceptions and, in the end, limited the statute to

the ones set forth.”11

Indeed, the enumerated series in § 102 must be

interpreted as exhaustive leaving no room for others

unlisted given the statutory construction canon

expressio unius est exclusio alterius, that is, “[t]he

10 Almendarez-Torres v. United States, 523 US 224, 234 (1998)

(cleaned up).

11 United States v. Johnson, 529 US 53, 58 (2000) (emphasis

added).

-9expression of one thing implies the exclusion of

others.” 12 This canon is strongest here, “when the

items expressed are members of an ‘associated group

or series,’ justifying the inference that items not

mentioned were excluded by deliberate choice, not

inadvertence.”13 Accordingly, neither the courts nor

the PTO can create other extra-statutory exceptions

through equitable doctrines forcing forfeiture that

result in “loss of right to patent.”

“When a statute limits a thing to be done in a

particular mode, it includes a negative of any other

mode.” 14 Specifically, Congress has expressly

specified the modes for forfeiture of the patent right,

and did so under § 102(b) for inventions in “public

use” or “on sale” more than one year prior to the

priority filing date, in § 102(c) for abandonment of

the invention, and in § 102(g) in timeliness

consideration of the “reasonable diligence of one who

was first to conceive and last to reduce to practice.”

For example under the “on sale” bar, “a patentee is

not allowed to derive any benefit from the sale or use

of his machine, without forfeiting his right, except

within the” grace period prior to filing the

application. 15 Forfeiture for abandonment of the

12 Antonin Scalia and Bryan A. Garner, Reading Law: The

Interpretation of Legal Texts (Thomson/West 2012) (§10

Negative-Implication Canon).

13 Barnhart v. Peabody Coal Co., 537 U.S. 149, 168 (2003).

14 Raleigh & Gaston R. Co. v. Reid, 80 US 269, 270 (1872).

15 Metallizing Engineering Co. v. Kenyon Bearing & AP Co.,

153 F. 2d 516, 519 (2nd Cir. 1946) (emphasis added); See same

result under post-AIA law in Helsinn Healthcare S.A. v. Teva

Pharmaceuticals USA, Inc., 139 S. Ct. 628 (2019).

- 10 invention under § 102(c) may arise in circumstances

evidencing constructive dedication of the invention

to the public, as described in the case In re Gibbs,

437 F.2d 486 (CCPA 1971) (“constructive

abandonment is often referred to as ‘statutory

forfeiture.’”) In conclusion, Congress prescribed by

law that forfeiture of the patent right can only occur

under these statutes and left no room for equitable

doctrines of forfeiture.

III. The doctrine of prosecution laches

contravenes the “shall have the same

effect” clause of § 120

35 U.S.C. § 120 in the 1952 Patent Act provided

a series of conditions and constraints for statutorycompliant continuing applications. Those conditions

are enumerated in § 120 by their components, as

rewritten with component numbers added in

brackets below (emphasis added):

Benefit of earlier filing date in the United

States

[1] An application for patent for an invention

disclosed in the manner provided by the first

paragraph of section 112 of this title

[2] in an application previously filed in the

United States

[3] by the same inventor

[4] shall have the same effect, as to such

invention, as though filed on the date of the

prior application,

[5] if filed before the patenting or

- 11 [6] abandonment of or

[7] termination of proceedings on the first

application or

[8] on an application similarly entitled to the

benefit of the filing date of the first application

and

[9] if it contains or

[10] is amended to contain a specific reference

to the earlier filed application.

Here too, the detailed list of ten (10) statutory

conditions must be interpreted as exhaustive under

the negative implication canon of expressio unius est

exclusio alterius. 16 Thus, by § 120, Congress

guaranteed that filing of a continuing application

within those enumerated conditions, subject to no

other extra-statutory conditions, “shall have the

same effect … as though filed on the date of the prior

application.”

However, forfeiture of patent rights in a

continuing application that meets all of § 120

conditions by invoking prosecution laches rejection

contravenes the statutory guarantee that its filing

“shall have the same effect … as though filed on the

date of the prior application,” because such forfeiture

denies

that

statutory-compliant

continuing

application the same effect. Indeed, the Federal

Circuit’s predecessor court explained that “justice

and reason … require that § 120 be held applicable

16 Scalia and Garner, Reading Law (2012) (§10 Negative-

Implication Canon); Barnhart, 537 U.S. at 168.

- 12 to all bases for rejection, that its words ‘same effect’

be given their full meaning and intent.”17

Clearly, the statutory guarantee in § 120

permits no exceptions, equitable or otherwise.

Congress did not permit any equitable judgment that

prosecution delay was not “unreasonable” as a

required condition for the filing to “have the same

effect.” The statutory requirement that it “shall have

the same effect” includes the effect of enforceability

and such effect cannot be disturbed by interjecting

any extra-statutory judgement that a filing was

“unreasonably delayed.” Doing so completely

emasculates § 120.

IV. Congress knows when to make equitable

doctrines available

In the 1946 Lanham Trademark Act, 18

Congress provided express provisions making

equitable doctrines, including laches, available in

the courts and in the PTO. Those include (emphasis

added below):

x 15 U.S.C. § 1069 (“In all inter partes proceedings

equitable principles of laches, estoppel, and

acquiescence, where applicable may be considered

and applied.”)

x 15 U.S.C. § 1115(b)(9) (expressly providing that

trademark infringement “shall be subject to the

… defenses … [t]hat equitable principles,

including laches, estoppel, and acquiescence, are

applicable.”)

17 In re Hogan, 559 F.2d 595, 604 (CCPA 1977).

18 Pub.L. 79-489, 60 Stat. 427 (July 5, 1946).

- 13 x

15 U.S.C. § 1116(a) (“The several courts… shall

have power to grant injunctions, according to the

principles of equity…”)

x 15 U.S.C. § 1117(a) (“plaintiff shall be entitled,

subject to the principles of equity, to recover… (1)

defendant’s profits, (2) any damages sustained by

the plaintiff, and (3) the costs of the action.”)

The Patent Act and the Trademark Act reflect

fundamentally different congressional approaches to

timeliness, and those differences explain why

Congress expressly directed equitable doctrines to be

applied in trademark law but not in patent law when

the Patent Act was enacted six years later in 1952.

In the Patent Act, Congress created a

comprehensive

and

self-contained

statutory

timeliness framework governing the creation,

duration, prosecution, challenge, and enforcement of

patent rights. Patentability itself is barred if the

inventor delays filing beyond the statutory limits set

forth in 35 U.S.C. § 102. Once an application is filed,

the applicant must respond to PTO actions within

six months under 35 U.S.C. § 133 or the application

is abandoned. If a patent issues, its term is fixed and

expires twenty years from filing under 35 U.S.C. §

154, regardless of any equitable considerations.

Administrative challenges are subject to strict

statutory deadlines, including seeking interference

under 35 U.S.C. § 135 with an issued patent no later

than one year after it issues. Enforcement is likewise

governed by statute: 35 U.S.C. § 286 limits damages

recovery to infringement occurring within six years

before suit. These provisions collectively define the

legal consequences of failing to meet the timeliness

requirements at every stage. Because Congress itself

specified the timelines modalities, and failure to

- 14 meet them results in forfeiture, expiration, or

limitation of recovery, there were no statutory gaps

requiring

equitable

doctrines

determine

timeliness or to limit remedies.

By contrast, the Trademark Act of 1946 left

major aspects of timeliness undefined by statute.

Trademark rights arise from use, and there is no

statutory analogue to 35 U.S.C. § 102 that bars

registration or enforcement based on delay in filing

after first use. Trademark rights may continue

indefinitely so long as statutory renewal filings are

made, and there is no fixed statutory term

comparable to the patent term in § 154.

Significantly, the Lanham Act contains no statutory

limitation period equivalent to 35 U.S.C. § 286

restricting recovery of damages for infringement,

and no statutory deadline for bringing infringement

actions after rights are violated. In this statutory

environment, delay does not automatically result in

forfeiture or limitation by operation of statute.

Provisions for cancellation of a registered mark

exemplify this point. Under the Lanham Act, certain

cancellation grounds are expressly perpetual and

may be asserted “at any time,” reflecting Congress’s

determination that these defects invalidate

trademark rights regardless of the passage of time.

Specifically, a registration may be cancelled at any

time if the mark has become generic (15 U.S.C. §

1064(3)); if the mark has been abandoned through

discontinued use or loss of source significance (15

U.S.C. §§ 1064(3), 1127); if the registration was

obtained fraudulently (15 U.S.C. § 1064(3)); if the

mark consists of functional matter that trademark

law cannot protect (15 U.S.C. § 1064(3)); or if the

mark was improperly registered in violation of

- 15 statutory prohibitions, including false suggestion of

connection, use of governmental insignia, or use of

the name or likeness of a living person without

consent (15 U.S.C. §§ 1052(a)–(c), 1064(3)). In

addition, certification marks remain perpetually

subject to cancellation if the registrant fails to

control their use, discriminates in certification, or

otherwise ceases to function as a legitimate certifier

(15 U.S.C. § 1064(5)). These perpetual cancellation

provisions operate without statutory time limitation

and are therefore expressly subject to equitable

defenses such as laches, estoppel, and acquiescence

in inter partes proceedings (15 U.S.C. § 1069).

Congress addressed these statutory omissions

not by imposing fixed timing rules, but by expressly

directing courts and authorizing the PTO to apply

equitable principles. The Lanham Act provides that

monetary recovery is available “subject to the

principles of equity” in 15 U.S.C. § 1117(a), that

equitable defenses such as laches and estoppel may

bar enforcement under 15 U.S.C. § 1115(b)(9), and

that equitable principles including laches may be

applied in administrative proceedings under 15

U.S.C. § 1069. These provisions expressly delegate to

adjudicators the authority to determine the legal

consequences of delay where Congress did not define

timeliness requirements by statute.

It is instructive and significant that the three

trademark statutes listed above in 15 U.S.C.

§§ 1115(b)(9), 1116(a), and 1117(a), all directed to

Article III courts, employ the imperative “shall” in

directing the court to apply principles of equity,

whereas 15 U.S.C. § 1069 on inter partes

proceedings at an agency (the PTO) employ the

permissive “may” in authorizing the PTO to consider

- 16 and apply specifically enumerated equitable

principles. Congress does not “hide elephants in

mouseholes.”19

This reflects that when Congress intends

equitable doctrines to operate in adjudication, it

provides express, tribunal-specific instructions.

Administrative tribunals such as the PTO possess no

inherent equitable authority, so §1069 affirmatively

authorizes it, in inter partes proceedings, to

“consider and apply” laches, estoppel, and

acquiescence. But Congress did not rely on courts’

inherent equitable powers either. In parallel

provisions governing infringement and remedies, it

directed Article III courts to adjudicate claims

“subject to the principles of equity” and to grant

relief “according to the principles of equity,” thereby

making equitable doctrines an integral component of

judicial decisionmaking rather than a matter left to

background discretion. Read together, these

provisions show a deliberate statutory design:

Congress specified the role of equity separately for

each tribunal and calibrated how strongly they

should apply —permissively for the PTO, and as an

obligatory governing framework for courts—

demonstrating that when Congress intends

equitable doctrines to apply in adjudication, it does

so through explicit and differentiated statutory

commands, not by implication.

The contrast between the two Acts reflects

deliberate legislative design. In the Patent Act,

Congress specified timeliness requirements and

19 Whitman v. American Trucking Assns., Inc., 531 US 457, 468

(2001).

- 17 their consequences directly, leaving no role for

equity in determining forfeiture or entitlement to

relief. In the Trademark Act, Congress instead left

critical timing issues unresolved by statute and

expressly authorized equity to govern those issues.

The presence of express equitable authority in

trademark law, and its relative absence in patent

law enacted shortly thereafter, reflects not a

difference in judicial tradition but a difference in

statutory completeness.

The Trademark Act shows that Congress knew

how to make equitable doctrines available where

needed. Where Congress intends the equitable

doctrine of prosecution laches to be specifically

available in patent cases, it knows how to provide so

expressly by law. In the Special Act of March 2, 1901,

56th Cong. 2nd Sess., 31 Stat. 1788. Ch. 821,

Congress referred the claim of William E.

Woodbridge to the Court of Claims, instructing that

“the said court shall first be satisfied that the said

Woodbridge did not forfeit, or abandon, his right to a

patent, by publication delay, laches, or otherwise;

and that the said patent was wrongly refused to be

issued by the Patent Office” (emphasis added).

This Court has repeatedly treated Congress’s

decision to include a particular mechanism in one

statute but omit it in another as evidence of

deliberate legislative choice because Congress “knew

how to do so.” Custis v. United States, 511 U.S. 485,

492 (1994) (“when Congress intended to authorize

collateral attacks on prior convictions at the time of

sentencing, it knew how to do so. Congress' omission

of similar language in § 924(e) indicates that it did

not intend to give defendants the right to challenge

the validity of prior convictions under this statute.”)

- 18 That reasoning applies here, confirming that

Congress intended that, contrary to the Trademark

Act, no equitable timeliness doctrine would be

applied under the Patent Act.

V. The Patent Act’s framework specifically

facilitates prosecuting continuing

applications over many years

Patent prosecution practice at the PTO has

long provided for multiple types of continuing patent

applications. Prior to the 1952 Patent Act, the first

edition of the PTO’s Manual of Patent Examining

Procedure (“MPEP”) dated November, 1949,

describes a divisional application as “[a] later

application for a distinct or independent invention,

carved out of a pending application,” § 201.06; a

continuation application as “a second application

for the same invention claimed in a prior application

and filed before the original becomes abandoned,”

§ 201.07; and a continuation-in-part application

as “an application filed during the lifetime of an

earlier application by the same applicant, repeating

some substantial portion or all of the earlier

application and adding matter not disclosed in the

said earlier case.” § 201.08.

This 1949 edition of the MPEP further adds in

§ 201.11 (emphasis added):

A division, continuation, or continuation-inpart is linked by co-pendency with the original

or parent application; and contains, in whole or

in part, identical disclosure in common with the

original application. Such applications are

entitled to the effective filing date of the

original application for only the common

subject

matter

disclosed.

division,

- 19 continuation, or continuation-in-part may be

filed at any time during the pendency of the

parent application. Such continuing application

may be filed, for example, after an appeal to the

Board or to the Court, provided the parent

application has not become abandoned.

The Patent Act essentially codified this proven

pro-innovation practice in §§ 101, 120 and 121,

which expressly provide for objective and necessary

circumstances where filing continuing applications

claiming priority to a single original application

spans many years. The Federal Circuit has

acknowledged that filing continuing applications

after substantial periods of prosecution of parent

applications include (i) filing a divisional application

in response to a restriction requirement—even as

late as just before issuance of the parent application;

(ii) refiling an application to present new evidence of

an invention's unexpected advantages; and (iii)

refiling an application to add subject matter to

attempt to support broader claims as the

development of an invention progresses, and for

other reasons.20

These are but some circumstance, and “[t]he

exigencies of prosecution commonly compel the

issuance

interrelated

applications

with

overlapping disclosures at widely divergent times.”21

Experimentation and development over time has

20 Symbol Techs., Inc. v. Lemelson Med., 422 F.3d 1378, 1385

(Fed. Cir. 2005) (“Symbol II”).

21 In re Sarett, 327 F.2d 1005, 1011 (CCPA 1964) (emphasis

added).

- 20 salutary effects of the scope of patent rights. Claims

in patents issued from continuing applications

appear better matched to commercial applications,

as such patents are empirically shown to have

greater private value.22 Moreover, legislative history

shows that Congress expected “several patents” to

issue from a single parent application. 23 Clearly,

Congress expressly “allow[ed] multiple links of such

‘continuation’ applications in a chain leading back to

an earlier application as long as each link meets

[§ 120’s] requirements,” 24 and large chains of

continuing applications are not uncommon. For

example, PTO data for 2025 shows that of the

applications allowed over one year, there were 6,180

having five or more parents in their chain of benefit

22 Cesare Righi, et al., “Continuing patent applications at the

USPTO,” 52 Research Policy, 104742 (2023) (Finding “that

continuing application patents have higher private value than

original patents: they are more likely to be renewed, litigated,

reassigned, used as collateral, licensed, used to protect drugs

listed in the Orange Book, or declared essential for information

and communication technology (ICT) standards; according to

most measures, they are also more valuable than their own

parents.”)

23 Senate Rep. 82-1979, “Revision of Title 35, United States

Code,” at 20 (June 27, 1952) (Recognizing that an application

can be “divided in several patents” under Section 121).

24 Immersion Corp. v. HTC Corp., 826 F.3d 1357, 1360 (Fed.

Cir. 2016); see also In re Henriksen, 399 F.2d 253, 261 (CCPA

1968) ("We hold that there is no limit to the number of prior

applications through which a chain of copendency may be

traced to obtain the benefit of the filing date of the earliest of a

chain of prior copending applications.")

- 21 claim and 832 applications were with ten or more

such parents in the chain.25

V.A

The American “Prospecting Patent

Bargain” for disclosing improvements in

Continuation-In-Part applications over

“widely divergent times”

The Patent Act in 35 U.S.C. § 101 provides for

obtaining a patent for inventions and also for “any

new and useful improvement thereof … subject to the

conditions and requirements of this title” (emphasis

added). One of the “conditions and requirements” for

obtaining the exclusive patent right is specified in

the first paragraph of 35 U.S.C. § 112, which

requires the specification to include the written

description and enablement of the invention and

“shall set forth the best mode contemplated by the

inventor of carrying out his invention” (emphasis

added). This quid pro quo is commonly referred to as

the “patent bargain.” The Supreme Court explained:

By the patent laws Congress has given to the

inventor opportunity to secure the material

rewards for his invention for a limited time, on

condition that he make full disclosure for the

benefit of the public of the manner of making

and using the invention, and that upon the

25 PTO, “Studying Applications with Large Patent Families,”

(June 2025) (Slide 8). Available at

www.uspto.gov/sites/default/files/documents/USPTO_Hour_Lar

ge_Patent_Family_Study_Final_06042025_CleanCopy_brand50

8c.pdf

- 22 expiration of the patent the public be left free to

use the invention.26

Once such disclosure is made in an original

patent application, the inventor may later file a

continuing application subject to the requirements of

§ 120, including that the invention be “disclosed in

the manner provided by the first paragraph of

section 112.” To be sure, divisional and continuation

applications must contain specifications identical to

those in the parent application, which must already

comply with the first paragraph of § 112. Had

Congress intended to limit continuing applications

only to these two types of applications, there would

have been no need to expressly repeat in § 120 the

requirement of the first paragraph of § 112.

However, this text is not surplusage.27 In including

this text in § 120, Congress specifically provided for

circumstances in which the written description,

enablement, or “best mode” disclosures may differ

from that in the parent application. It is this aspect

of § 120 that particularly creates the statutory