Federal Preemption and State Authority to Deter the Presence of Unlawfully Present Aliens: An Overview and Issues for the 119th Congress
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Federal Preemption and State Authority to
Deter the Presence of Unlawfully Present
Aliens: An Overview and Issues for the 119th
Congress
May 6, 2025
Congressional Research Service
https://crsreports.congress.gov
R48525
SUMMARY
Federal Preemption and State Authority to
Deter the Presence of Unlawfully Present
Aliens: An Overview and Issues for the 119th
Congress
R48525
May 6, 2025
Alejandra Aramayo
Legislative Attorney
The Supremacy Clause of the U.S. Constitution (Article VI, clause 2) states that the Constitution,
treaties, and federal law “shall be the supreme Law of the land.” In interpreting this clause, the Supreme Court has formulated
the doctrine of preemption, under which federal law supersedes conflicting state measures. In examining cases, the Court has
identified two general ways in which a state law must yield or is preempted by a federal law—where a federal law expressly
preempts state law or where a federal law impliedly preempts a state law. Congressional intent is the “ultimate touchstone” in
determining whether state law is expressly or impliedly preempted. The Court has further held that, in the absence of explicit
preemptive language, there are two types of implied preemption: field preemption, where Congress legislated in a particular
field or area of law “so pervasive” that it “left no room for the States to supplement it”; and conflict preemption, where it is
impossible to comply with both federal and state law or where a state law has created “an obstacle to the accomplishment of
the full purposes and objectives of Congress.”
The power to prescribe rules as to which aliens may enter the United States and which aliens may be removed resides solely
with the federal government—and primarily with Congress. Pursuant to its broad power, Congress has enacted various laws,
primarily contained in the Immigration and Nationality Act of 1952, as amended, that regulate not only the entry and removal
of aliens but also many aspects of aliens’ presence within the United States, including employment eligibility. The Supreme
Court has observed that, while Congress has established a comprehensive framework to regulate immigration, not every state
measure “which in any way deals with aliens is a regulation of immigration and thus per se preempted.”
This report examines the interplay between federal regulation of immigration and state measures that seek to deter the
presence of aliens within their jurisdictions who are believed to be in the United States unlawfully. In particular, this report
discusses how courts have resolved conflicts between state and federal law in this area. For example, in 2010, Arizona passed
a law that, among other things, gave police authority to stop anyone they suspected of being in the United States unlawfully
and to request proof of immigration status. The Arizona law also made it unlawful to work in Arizona without federal work
authorization. A group of plaintiffs sued the state, claiming that the state was barred from legislating in these areas. In 2012,
the Supreme Court held in Arizona v. United States that many aspects of the Arizona measure of were impliedly preempted
by federal immigration law. The Supreme Court most recently resolved a dispute over the preemptive effect of federal
immigration law on state measures in the Court’s 2020 decision, Kansas v. Garcia. The challengers argued that the Kansas
statutes, which made it a crime to commit identity theft or engage in fraud to obtain a benefit, were preempted as applied to
the prosecution of an unauthorized alien’s use of false documents to obtain employment. The Court rejected these arguments,
holding that Kansas’s criminal statutes were not expressly or impliedly preempted because the governing federal law did not
bar states from the entire field of employment verification and it was possible to comply with both federal and state law.
In recent years, states have enacted laws to, among other things, criminalize an alien’s presence in their jurisdictions if the
alien unlawfully entered or reentered into the United States. In legal challenges to these measures, plaintiffs raise similar
preemption arguments to those made in the Arizona case. The defendant states counter by arguing, in part, that federal law
does not preempt states’ authority to defend their borders when they have been “invaded.” This theory, informed by Justice
Scalia’s partial dissent in Arizona, rests on the notion that the sovereignty of a state includes the right to exclude people who
have no right to be in the United States. Some states argue that federal immigration cannot preempt a state law enacted
pursuant to its sovereign right protect itself against an “invasion” if, in their view, the federal government has failed to defend
the state against such invasion.
Lastly, this report discusses considerations for Congress, including describing proposals introduced by some Members of
Congress aimed at addressing conflicts over states’ ability to deter the presence of unlawfully present aliens within their
jurisdictions. In particular, there have been proposals that would constrain or enhance states’ ability to take action to deter the
presence within their jurisdictions of aliens who lack federal permission to enter or remain in the United States.
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Federal Preemption and Immigration: State Laws Deterring Unlawfully Present Aliens
Contents
Introduction ..................................................................................................................................... 1
Congressional Authority to Regulate Immigration .......................................................................... 2
The Supremacy Clause and Preemption in Immigration Cases ...................................................... 4
Express Preemption................................................................................................................... 4
Implied Preemption ................................................................................................................... 5
Field Preemption ................................................................................................................. 5
Conflict Preemption ............................................................................................................ 6
Preemption and Immigration: Select Supreme Court Decisions ..................................................... 6
Hines v. Davidowitz (1941) ....................................................................................................... 6
De Canas v. Bica (1976) ........................................................................................................... 8
Chamber of Commerce v. Whiting (2011) ................................................................................. 9
Arizona v. United States (2012)............................................................................................... 10
Kansas v. Garcia (2020) .......................................................................................................... 15
Preemption and Immigration: Select Cases Pending in Lower Courts.......................................... 17
Texas, S.B. 4 (United States v. Texas) ..................................................................................... 18
Oklahoma, H.B. 4156 (United States v. Oklahoma) ............................................................... 23
Iowa, S.F. 2340 (United States v. Iowa) .................................................................................. 24
Other Recent State Measures Addressing Unlawfully Present Aliens .................................... 27
Considerations for Congress.......................................................................................................... 28
Contacts
Author Information........................................................................................................................ 30
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Federal Preemption and Immigration: State Laws Deterring Unlawfully Present Aliens
Introduction
The Supreme Court has recognized that the power to prescribe rules as to which aliens1 may enter
the United States and which aliens may be removed resides solely with the federal government,
and primarily with Congress.2 Congress’s authority to enact laws regulating immigration derives
from its Article I constitutional powers to, among other things, “establish an uniform Rule of
Naturalization” and to regulate foreign commerce.3 More broadly, the Supreme Court has
described the immigration power as flowing from the federal government’s inherent authority
over the nation’s borders and the conduct of foreign relations.4 Pursuant to this authority,
Congress has enacted various laws regulating not just the entry and removal of aliens but also
many aspects of those persons’ continued presence in the United States.5
The Supremacy Clause of the U.S. Constitution provides, in part, that “the Laws of the United
States ... shall be the supreme Law of the Land.”6 In interpreting this clause, the Supreme Court
formulated the doctrine of federal preemption, and, under this constitutional mandate, courts are
required to determine whether a state or local law regulating in a particular issue area is
preempted by federal law. The Supreme Court has held that “[t]he passage of laws which
concerns the admissions of citizens and subjects of foreign nations ... belongs to Congress, and
not to the States.”7 Courts have generally held that state and local measures that intrude upon or
interfere with the federal government’s regulation of immigration are preempted, even when such
measures are directed at aliens who lack legal permission from the federal government to enter or
remain in the United States.8 Nevertheless, while Congress’s authority over immigration is well
established, the Supreme Court has never recognized that any state law “which in any way deals
with aliens is a regulation of immigration and thus per se preempted.”9 Therefore, in determining
whether a state or local law—which has the effect of deterring the presence of unlawfully present
1 “The term ‘alien’ means any person not a citizen or national of the United States.” See 8 U.S.C. § 1101(a)(3). Some
have criticized the statutory term as offensive, but avoiding its use in legal analysis is difficult because the term is
woven deeply into the statutory framework. Compare Trump v. Hawaii, 585 U.S. 667, 746 n.7 (2018) (Sotomayor, J.,
dissenting) (“It is important to note ... that many consider ‘using the term “alien” to refer to other human beings’ to be
‘offensive and demeaning.’ I use the term here only where necessary ‘to be consistent with the statutory language’ that
Congress has chosen and ‘to avoid any confusion in replacing a legal term of art with a more appropriate term.’”)
(quoting Flores v. U.S. Citizenship & Immigr. Servs., 718 F.3d 548, 551–52 n.1 (6th Cir. 2013), abrogated by Sanchez
v. Mayorkas, 593 U.S. 409 (2021)) with Avilez v. Garland, 69 F.4th 525, 541 (9th Cir. 2022) (Bea, J., concurring)
(“Federal courts applying federal immigration laws should not invent their own terminology to stand in place of
definitions used in the congressional statutes they are tasked with applying.”).
2 Oceanic Steam Navigation Co. v. Stranahan, 214 U.S. 320, 343 (1909) (describing the “plenary power of Congress as
to the admission of aliens” and “the complete and absolute power of Congress over” immigration); see also Galvan v.
Press, 347 U.S. 522, 531 (1954).
3 See U.S. CONST. art. I, § 8, cl. 3, 4; Toll v. Moreno, 458 U.S. 1, 10 (1982).
4 See, e.g., Arizona v. United States, 567 U.S. 387, 394 (2012) (discussing the foreign relations power); Nishimura Ekiu
v. United States, 142 U.S. 651, 659 (1892) (“It is an accepted maxim of international law that every sovereign nation
has the power, as inherent in sovereignty, and essential to self-preservation, to forbid the entrance of foreigners within
its dominions, or to admit them only in such cases and upon such conditions as it may see fit to prescribe.”).
5 See infra “Congressional Authority to Regulate Immigration.”
6 U.S. CONST. art. VI, cl. 2.
7 Chy Lung v. Freeman, 97 U.S. 275, 280 (1875).
8 See Arizona, 567 U.S. at 416 (“The National Government has significant power to regulate immigration.... Arizona
may have understandable frustrations with the problems caused by illegal immigration ... , but the State may not pursue
policies that undermine federal law.”).
9 De Canas v. Bica, 424 U.S. 351, 355 (1976).
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aliens—is valid, courts must take into consideration congressional intent in determining whether
federal law preempts state law.10
This report provides an overview of preemption as it applies to potential conflicts between federal
immigration law and state and local efforts to deter the presence of aliens believed to be in the
United States without authorization.11 The report begins by providing a brief overview of
congressional authority to regulate the entry and removal of aliens and the doctrine of
preemption. The report then examines notable Supreme Court decisions from the mid-20th
century onward that have considered preemption challenges to state laws seeking to deter the
presence of unlawfully present aliens. In particular, the report discusses the scope and
implications of the Supreme Court’s 2012 ruling in Arizona v. United States, where the Court held
that Arizona’s attempt to “discourage and deter the unlawful entry and presence of aliens” was
preempted. The report also discusses the Court’s 2020 decision in Kansas v. Garcia, where the
Court held that Kansas’s statutes that make it a crime to commit identity theft or engage in fraud
to obtain a benefit was neither expressly nor impliedly preempted.
The report then provides an overview of states’ recent efforts to criminally deter the presence of
unlawfully present aliens within their borders and the ensuing litigation following the Court’s
opinions in Arizona and Kansas. Some states have argued that neither Congress nor the executive
branch has properly addressed their immigration concerns and that they maintain sovereign
authority to exclude the presence of persons who have “invaded” their borders.12 Lastly, the
report identifies several considerations for Congress and summarizes recent proposals to enhance
or constrain states’ ability to deter the presence within their jurisdictions of aliens who lack
federal permission to enter or remain in the United States.
Congressional Authority to Regulate Immigration
As mentioned above, the Supreme Court has repeatedly recognized that the federal government
exercises “broad, undoubted power over the subject of immigration and the status of aliens.”13
10 Fidelity Fed. Sav. and Loan Ass’n v. de la Cuesta, 458 U.S. 141, 152 (1982).
11 This report solely focuses on the legal analysis of preemption challenges as they relate to conflicts between federal
law and state laws that either directly or indirectly deter the presence of unlawfully present aliens. The area of
preemption and federal immigration law is vast and, in addition to the topics covered in this report, also includes
discussions regarding whether the Immigration and Nationality Act (INA) preempts state and local restrictions on
communications with federal immigration officials. These challenges regarding what has become known as “sanctuary”
policies highlight a tension between federal agencies and states and local jurisdictions. For further discussion regarding
the interplay between federal law and “sanctuary” jurisdictions, see CRS In Focus IF11438, “Sanctuary” Jurisdictions:
Policy Overview, coordinated by Abigail F. Kolker (2025).
12 See e.g., Defendants’ Consolidated Response in Opposition to Plaintiffs’ Motions for Preliminary Injunction at 22–
31, United States v. Texas, 719 F. Supp. 3d 640 (W.D. Tex. 2024) (No. 1:24-cv-00008-DAE), Dkt. No. 25; United
States v. Texas, 97 F.4th 268, 283 (5th Cir. 2024) (“The results of the lack of funding coupled with the lack of political
will are apparent. Texas, nobly and admirably some would say, seeks to fill at least partially the gaping void.”).
Commentators have stated that Texas enacted such laws in the hopes of bringing the issue of the federal government’s
broad power over immigration back to the forefront of the Supreme Court, as the Supreme Court declined to hear this
issue in the Arizona case. See Devan Cole, Texas Immigration Controversy Rekindles Fight Over Arizona’s ‘Show Me
Your Papers’ Law, CNN (Apr. 3, 2024, 11:43 AM), https://www.cnn.com/2024/04/03/politics/texas-immigration-lawsb-4/index.html. (quoting Governor Abbott’s statement to CNN that he welcomes a decision from the Supreme Court
that could overturn Arizona v. United States).
13 Arizona, 567 U.S. at 394. Federal authority over immigration derives from multiple sources. The Constitution
provides Congress with the authority “[t]o regulate Commerce with foreign Nations” and “[t]o establish an uniform
Rule of Naturalization.” U.S. CONST., Art. I, § 8, cl. 3-4. Federal authority to regulate the admission and presence of
aliens also derives from its authority over foreign affairs. See Toll v. Moreno, 458 U.S. 1, 10 (1982). The Supreme
(continued...)
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The Court has treated this power as primarily resting with Congress, with executive authority
generally deriving from statutory delegations of authority.14 The Court has characterized
Congress’s power over immigration as “plenary”15 and has observed that “Congress may make
rules as to aliens that would be unacceptable if applied to citizens.”16
Congress has established an “extensive and complex” set of rules governing the admission and
removal of aliens along with conditions for aliens’ continued presence within the United States,
including eligibility for employment and public benefits.17 These rules are primarily contained in
the Immigration and Nationality Act of 1952, as amended (INA).18 The INA supplements these
rules through an enforcement regime that contains criminal and civil provisions, which
sometimes sanction similar conduct.19 For example, unlawful entry by an alien into the United
States is both a criminal offense20 and a ground for removal from the United States.21 At the same
time, the INA provides several avenues by which an eligible alien, even if unlawfully present
within the country, may obtain relief from removal.22 The Supreme Court has characterized this
framework as conferring “broad discretion” to immigration officials, including in deciding
“whether it makes sense to pursue removal at all.”23
Congress has also created several avenues for states and localities to assist in the enforcement of
federal immigration law. For example, the Illegal Immigration Reform and Immigrant
Responsibility Act of 1996 amended the INA to permit the delegation of certain immigration
enforcement functions to state and local officers by way of cooperative agreements, commonly
known as 287(g) agreements.24 Another provision authorizes state and local authorities, after
obtaining confirmation from federal immigration authorities, to arrest unlawfully present criminal
aliens who have reentered the United States so that those aliens may be transferred to federal
custody.25 Other provisions allow state or local police to make arrests for certain federal
Court has also characterized control over immigration as a fundamental attribute of a national sovereign. Fiallo v. Bell,
430 U.S. 787, 792 (1977).
14 Galvan v. Press, 347 U.S. 522, 530 (1954) (“Policies pertaining to the entry of aliens and their right to remain here
are peculiarly concerned with the political conduct of government. In the enforcement of these policies, the Executive
Branch of the Government must respect the procedural safeguards of due process. But that the formulation of these
policies is entrusted exclusively to Congress has become about as firmly imbedded in the legislative and judicial tissues
of our body politic as any aspect of our government.”) (internal citations omitted).
15 Kleindienst v. Mandel, 408 U.S. 753, 766 (1972); Oceanic Steam Navigation Co. v. Stranahan, 214 U.S. 320, 343
(1909) (noting the plenary power of Congress as to the admission of aliens and the complete and absolute power of
Congress over the subject of immigration).
16 Demore v. Kim, 538 U.S. 510, 522 (2003).
17 See Arizona, 567 U.S. at 395–96; see also 8 U.S.C. §§ 1324a (barring the employment of aliens who are
unauthorized to work in the United States) and 1601–46 (limiting alien eligibility for public benefits).
18 8 U.S.C. §§ 1101, et seq.
19 For a brief discussion, see CRS In Focus IF11410, Immigration-Related Criminal Offenses (2023).
20 8 U.S.C. § 1324 (providing that unlawful entry is a criminal offense).
21 8 U.S.C. §§ 1182(a)(6)(A)(i) (providing that unlawful entry is a ground for removal).
22 See, e.g., id. § 1158 (allowing eligible aliens to apply for asylum within one year of entering the United States,
regardless of immigration status, if unable or unwilling to return to his or her country because of past persecution or a
well-founded fear of future persecution on account of race, religion, nationality, political opinion, or membership in a
particular social group).
23 Arizona, 567 U.S. at 396.
24 Pub L. No. 104-208, tit. III § 133, 110 Stat. 3009-563 (1996), codified at 8 U.S.C. § 1357(g)(1).
25 8 U.S.C. § 1252c.
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immigration crimes.26 In other cases, a federal immigration statute may specify that it does not
displace state or local measures that address similar topics.27
In recent decades, many of the most prominent preemption challenges to state and local measures
have involved efforts to deter aliens believed to be unlawfully present in the United States from
residing in the state or municipality.28 Those bringing forth a suit challenging the state’s action
assert that federal immigration law preempts state regulation. To better understand these complex
and interconnected issues, a brief overview of the doctrine of preemption is necessary.
The Supremacy Clause and Preemption in
Immigration Cases
Article VI, clause 2, of the U.S. Constitution, also known as the Supremacy Clause, provides that
the Constitution, treaties, and federal laws are “the supreme Law of the Land.”29 The Supremacy
Clause is the foundation for the doctrine of federal preemption, under which federal law
supersedes conflicting state measures.30 The Supreme Court has held that when analyzing
whether a state or local measure is preempted, “[c]ongressional intent is the touchstone.”31 The
Supreme Court has identified two categories of preemption: express and implied preemption.32
Express Preemption
Express preemption occurs when Congress enacts a statute and the language of the statute
explicitly details its preemptive intent.33 When Congress includes such language, it is expressing
its intent to “withdraw specified powers from the States.”34 The Supreme Court has held that
26 See, e.g., id. §1324(c) (authorizing “officers whose duty it is to enforce criminal laws” to make arrests for violations
of the alien smuggling and harboring statute).
27 Id. § 1324a(h)(2) (preempting states from imposing additional criminal or civil penalties on employers of
unauthorized aliens “other than through licensing and similar laws”).
28 See e.g., Villas at Parkside Partners v. City of Farmers Branch, 726 F.3d 524 (5th Cir. 2013) (holding that an
ordinance that prevented rental housing to unlawfully present individuals was preempted because, among other things,
by creating criminal offense provisions it disrupted the existing federal immigration framework and covered more
unlawful conduct than the existing federal anti-harboring statute); Keller v. City of Fremont, 719 F.3d 931 (8th Cir.
2013) (holding that an ordinance that prevented rental housing to unlawfully present individuals was not preempted
because, among other things, it did not physically remove anyone from the city and immigration officials still had full
discretion in deciding when and whether to pursue removal proceedings); Lozano v. City of Hazleton, 724 F.3d 297 (3d
Cir. 2013) (holding that ordinances that prevented rental housing to unlawfully present individuals and regulated
employment of individuals without work authorization were preempted because, among other things, they applied to a
wider group of people than currently existed under federal immigration law and interfered “with the federal
government’s discretion” over the removal process).
29 U.S. CONST. art. VI, cl. 2.
30 See United States v. Texas, 97 F.4th 268, 315–16 (5th Cir. 2024) (Oldham, J., dissenting) (“States possess
sovereignty concurrent with that of the Federal Government, subject only to limitations imposed by the Supremacy
Clause.” (internal quotation marks omitted) (quoting Tafflin v. Levitt, 493 U.S. 455, 458 (1990))). For a discussion of
preemption generally, see CRS Report R45825, Federal Preemption: A Legal Primer, by Bryan L. Adkins, Alexander
H. Pepper, and Jay B. Sykes (2023).
31 Texas, 97 F.4th at 298 (5th Cir. 2024) (Oldham, J., dissenting) (citing to Cipollone v. Liggett Grp., Inc., 505 U.S.
504, 516 (1992)).
32 Gade v. Nat’l Solid Wastes Mgmt. Ass’n, 505 U.S. 88, 98 (1992).
33 Id. For a discussion regarding the language commonly used in express preemption clauses, see CRS Report R45825,
Federal Preemption: A Legal Primer, by Bryan L. Adkins, Alexander H. Pepper, and Jay B. Sykes (2023).
34 Arizona v. United States, 567 U.S. 387, 399 (2012).
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“[w]hen a federal law contains an express preemption clause, [the Court] focus[es] on the plain
wording of the clause, which necessarily contains the best evidence of Congress’s preemptive
intent” to determine whether Congress has expressed an intent to displace state authority.35 The
Court has further held that it considers in its analysis as to whether Congress intended to supplant
state authority the “statutory framework surrounding” the statute and the “structure and purpose
of the statute as a whole, as revealed not only in the text, but through the reviewing court’s
reasoned understanding of the way in which Congress intended the statute” to operate.36
Implied Preemption
The Supreme Court has recognized that implied preemption can occur in one of two ways—when
a state tries to regulate conduct in a field that Congress dominantly regulates (known as field
preemption)37 or when compliance with both state and federal law is impossible or when a state
law obstructs Congress’s objectives (known as conflict preemption).38
Field Preemption
The Supreme Court has held that states cannot regulate conduct “in a field that Congress, acting
within its proper authority, has determined must be regulated by its exclusive governance.”39 The
Court has determined that the intent behind displacing a state law can be inferred from “a
framework of regulation ‘so pervasive ... that Congress left no room for the States to supplement
it’ or where there is a ‘federal interest ... so dominant that the federal system’ precludes
enforcement of ‘state laws on the same subject.’”40 The Court has indicated a hesitancy to infer
field preemption unless a plaintiff can show that Congress clearly manifested this intention in
federal law.41 It has been observed that the Court “has never extended field preemption to any part
of the immigration laws beyond alien registration.”42 Finally, when a court analyzes field
preemption claims, “the relevant field should be defined narrowly.”43
35 Chamber of Commerce v. Whiting, 563 U.S. 582, 594 (2011) (“When a federal law contains an express preemption
clause, we focus on the plain wording of the clause, which necessarily contains the best evidence of Congress’
preemptive intent.” (internal quotation marks omitted)).
36 Medtronic, Inc. v. Lohr, 518 U.S. 470, 486 (1996) (citations and internal quotation marks omitted). In evaluating
congressional intent, the Supreme Court has held that its interpretation of a statute “does not occur in a contextual
vacuum” and that its interpretation must be “informed by two presumptions”—that states are independent sovereigns
and that courts must “start with the assumption that the historic police powers of the States were not to be superseded
by the Federal Act unless that was the clear and manifest purpose of Congress” and that an understanding of
Congress’s purpose in enacting the legislation “is the ‘ultimate touchstone’ in every preemption case.” Id. at 485–86.
37 See De Canas v. Bica, 424 U.S. 351, 356 (1976), superseded by statute, IRCA, Pub. L. No. 99-603, § 101, 100 Stat.
3359, 3360–74 (1986), as stated in Kansas v. Garcia, 589 U.S. 191 (2020); Arizona v. United States, 567 U.S. 387, 399
(2012); see also United States v. Texas, 97 F.4th 268, 278 (5th Cir. 2024) (stating that the field for field preemption
needs to be narrowly defined and that field preemption can be inferred when Congress has touched “a field in which the
federal interest is so dominant that the federal system” precludes states from enforcing its own laws in that same field
or subject).
38 Fla. Lime & Avocado Growers, Inc. v. Paul, 373 U.S. 142–43 (1963); Hines v. Davidowitz, 312 U.S. 52, 67 (1941).
39 Arizona, 567 U.S. at 399.
40 Id. (quoting Rice v. Santa Fe Elevator Corp., 331 U.S. 218, 230 (1947)).
41 See De Canas, 424 U.S. at 357; see also City of El Cenizo v. Texas, 890 F.3d 164, 176 (5th Cir. 2018).
42 Texas, 97 F.4th at 298 (5th Cir. 2024) (Oldham, J., dissenting).
43 City of El Cenizo, 890 F.3d at 177.
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Conflict Preemption
The Supreme Court has held that conflict preemption occurs where a state law “stands as an
obstacle to the accomplishment and execution of the full purposes and objectives of Congress”44
or where it is physically impossible to comply with both federal and state law.45 The Court has
described that determining what “is a sufficient obstacle is a matter of judgment, to be informed
by examining the federal statute as a whole and identifying its purpose and intended effects.”46
The Court has observed that, just because a state law may overlap with a federal law does not
automatically mean there is a case for conflict preemption.47 However, “conflict is imminent
when two separate remedies are brought to bear on the same activity.”48
Preemption and Immigration: Select Supreme Court
Decisions
Court decisions involving the relationship between state action and federal control over
immigration date as far back as the 1800s, when the Supreme Court held that states cannot tax
foreign vessels/nationals arriving into the United States.49 The following section surveys Supreme
Court decisions from mid-20th century onward that have been frequently invoked in litigation
concerning state and municipal action seeking to deter the presence of unlawfully present aliens
within their jurisdictions.
Hines v. Davidowitz (1941)
In 1939, Pennsylvania passed the Alien Registration Act, which, among other things, required all
aliens in the state over the age of 18 to register once a year and to carry and be ready to show a
registration card.50 In 1940, Congress passed the federal Alien Registration Act, which, among
other things, required aliens over the age of 14 to register with the federal government. Unlike the
Pennsylvania law, under the federal act, the individual was required to register only once and did
not have to carry or show a registration card.51 A group of plaintiffs challenged52 the validity of
the state law, and the Supreme Court determined that because Congress had created an exclusive
alien registration system through the Alien Registration Act of 1940 after Pennsylvania had, it had
to determine if the Pennsylvania law was invalid “in light of the congressional act.”53 The Court
44 Hines, 312 U.S. at 67.
45 See Arizona, 567 U.S. at 399.
46 Crosby v. Nat’l Foreign Trade Council, 530 U.S. 363, 373 (2000).
47 Kansas v. Garcia, 589 U.S. 191, 211–12 (2020).
48 Texas, 97 F.4th at 289 (internal quotation marks omitted).
49 See, e.g., New York v. Compagnie Generale Transatlantique, 107 U.S. 59 (1883). For further discussion on early
immigration jurisprudence and the interplay of federal and state immigration-related laws, see CONGRESSIONAL
RESEARCH SERVICE, UNITED STATES CONSTITUTION: ANALYSIS AND INTERPRETATION (CONSTITUTION ANNOTATED),
Immigration Jurisprudence (1837-1899), available at https://constitution.congress.gov/browse/essay/artI-S8-C18-85/ALDE_00001259/ and Immigration-Related State Laws, available at
https://constitution.congress.gov/browse/essay/artI-S8-C18-8-8-5/ALDE_00001268/ (last visited Apr. 30, 2025).
50 Hines, 312 U.S. at 59.
51 Id. at 60–61.
52 Davidowitz v. Hines, 30 F. Supp. 470, 472–73 (M.D. Pa. 1939).
53 Hines, 312 U.S. at 60.
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held that the congressional act occupied the field and that the Pennsylvania registration law had
been impliedly preempted.54
The Court began by briefly describing the Supremacy Clause and immigration preemption,
holding that when the federal government establishes, through either statute or treaty, the rules
and regulations that touch on “the rights, privileges, obligations or burdens of aliens,” that is the
“supreme law of the land.”55 The Court then focused much of its analysis on the importance of
the federal government’s “full and exclusive” role and responsibility “for the conduct of affairs
with foreign sovereignties” and that the “federal power in the field affecting foreign relations
[must] be left entirely free from local interference.”56 For example, the Court observed that one
important aspect of international affairs is being able to protect one’s own nationals when they are
in different countries.57 As a result, the Court explained that the United States has entered into
many treaties and abides by international customs and practices that are “aimed at preventing
injurious discriminations against aliens.”58 Therefore, the Court held that a state law that imposes
extraordinary or unusual burdens on aliens—who may otherwise be law-abiding—“to
indiscriminate and repeated interception and interrogation by public officials” affects all states
and provokes international affairs.59
Alien regulation, according to the Court, intimately blends and intertwines with the federal
government’s responsibilities, so when both Congress and a state act on the same subject, the
state has to yield to Congress.60 The Court held that because Congress, “in the exercise of its
superior authority in this field,” enacted a standard alien registration system, states cannot conflict
or interfere with it.61
The Court’s concluding analysis was whether the Pennsylvania law stood as an obstacle to
Congress’s objectives and purposes.62 According to the Court, “this legislation [was] in a field
which affects international relations, the one aspect of our government that ... demand[s] broad
national authority.”63 The Court agreed with the plaintiffs that the states do not have “the power to
restrict, limit, regulate, and register aliens” and that their power must be “subordinate to supreme
national law.”64 Nevertheless, the Court had to further determine if Congress acted in a way to
prevent the Pennsylvania law from being enforced.65 The Court briefly touched on Congress’s
history in providing the terms and conditions for an alien’s entry or removal and citizenship and
discussed how various bills had been introduced over the years regarding the registration of
aliens.66 Based on this analysis, the Court agreed with the plaintiffs that the Pennsylvania law was
preempted and held that because Congress “provided a standard for alien registration in a single
integrated ... system” to get necessary information from aliens, Congress likely desired uniformity
54 Id. at 72–74.
55 Id. at 62–64.
56 Id.
57 Id. at 64–65.
58 Id.
59 Id. at 65–66.
60 Id. at 66.
61 Id.
62 Id. at 67.
63 Id. at 68.
64 Id.
65 Id. at 69.
66 Id. at 69–71.
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and did so in a way “to leave them free from the possibility of inquisitorial practices and police
surveillance” that might affect international relations, among other things.67
De Canas v. Bica (1976)
In 1971, California passed a law that prohibited an employer from knowingly hiring “an alien
who is not entitled to lawful residence in the United States” if his or her employment would
adversely impact workers who are lawful residents.68 Migrant farmworkers sued their employers
(farm labor contractors) and alleged that their employers violated the California law because they
“had refused petitioners continued employment due to a surplus of labor resulting from [the farm
labor contractors’] knowing employment ... of aliens not lawfully admitted to residence in the
United States.”69 A California superior court held that the law was unconstitutional, finding that
the law “encroaches upon, and interferes with, a comprehensive regulatory scheme enacted by
Congress in the exercise of its exclusive power over immigration,” and dismissed the complaint.70
The California court of appeals affirmed the lower court’s decision, and the California Supreme
Court denied further review.71
The case was appealed to the Supreme Court, which reversed and remanded the lower courts’
decisions.72 The Court held that the California law was not preempted because “[s]tates possess
broad authority under their police powers to regulate the employment relationship to protect
workers within the State.”73 The Court further specified that it is within California’s police
powers to prevent California employers from hiring people who do not have lawful residence in
the country.74 The Court distinguished the facts in this case from Hines v. Davidowitz, observing
that the law being challenged in Hines was “in the specific field which the State [was] attempting
to regulate, while here there is no indication that Congress intended to preclude state law in the
area of employment regulation.”75
The Supreme Court held that, even though regulating immigration is a federal power, a state’s
enactment of a law “touching on aliens in general” does not mean that the state is trying to
regulate immigration and that therefore any such law should be automatically preempted.76 The
Court further held that the INA, although comprehensive, did not make references to the
employment of aliens and that therefore states were not precluded from regulating in this field.77
At the time this case was decided, Congress had not yet addressed the employment of
unauthorized aliens. Congress enacted Immigration Reform and Control Act (IRCA) in 1986,
which is incorporated into the INA and regulates the employment of aliens in the United States.78
67 Id. at 73–74.
68 De Canas v. Bica, 424 U.S. 351, 352 (1976), superseded by statute, IRCA, Pub. L. No. 99-603, § 101, 100 Stat.
3359, 3360–74 (1986), as stated in Kansas v. Garcia, 589 U.S. 191 (2020).
69 Id. at 353.
70 Id.
71 Id. at 353–54.
72 Id. at 352.
73 Id. at 353–54, 356.
74 Id.
75 Id.
76 Id. at 354–55.
77 Id. at 357–60.
78 See 8 U.S.C. § 1324a. For a more detailed review on federal regulation of alien employment and preemption, see this
(continued...)
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Chamber of Commerce v. Whiting (2011)
In 2007, Arizona passed the Legal Arizona Workers Act of 2007 (LAWA), which allowed state
courts to suspend or revoke business licenses if employers intentionally or knowingly hired aliens
who were unauthorized to work.79 LAWA also required that every employer within the state use
the federal government’s E-Verify system to confirm workers’ eligibility to work in the United
States.80 The plaintiffs, including the U.S. Chamber of Commerce and various organizations, filed
a lawsuit against the state arguing that these two aspects of LAWA were expressly and impliedly
preempted by federal law.81 Specifically, they argued that LAWA’s business license provision was
expressly and impliedly preempted by IRCA, which states that “[t]he provisions of this section
preempt any State or local law imposing civil or criminal sanctions (other than through licensing
and similar laws)” on those who employ unauthorized aliens.82 Further, they argued that the
requirement that all employers had to use E-Verify was impliedly preempted because, in their
view, Congress wanted a work authorization verification system that was not burdensome and
could “serve as an alternative to the I-9 procedures.”83 The plaintiffs contended that the
“mandatory use of E-Verify” would get in the way of that goal.84
The Supreme Court held that federal immigration law did not preempt the LAWA provisions at
issue.85 Because IRCA contains an express preemption clause, the Supreme Court first focused its
analysis on the plain wording of the clause, as it best shows Congress’s preemption intent.86 The
clause specifies that states cannot impose “civil or criminal sanctions” on employers who hire
unauthorized aliens except “through licensing and similar laws.”87 The Court held that LAWA, on
its face, imposed sanctions through licensing and therefore fell within the confines of the
authority Congress left to the states in IRCA.88 The plaintiffs argued that, although LAWA used
the term “licensing,” it was not being used in the same way as IRCA’s express preemption clause
and that this argument was further supported by the legislative history.89 The Court disagreed,
holding that LAWA’s licensing provision was not expressly preempted because the statute itself
served as Congress’s authoritative statement—not legislative history—and the plaintiffs did not
show a textual basis to limit the meaning of the phrasing in IRCA’s express preemption clause.90
CRS Legal Sidebar LSB10550, Federal Regulation of Alien Employment and Preemption over State Laws, by Hillel R.
Smith (2020).
79 Chamber of Commerce v. Whiting, 563 U.S. 582, 591 (2011).
80 Id. at 593. E-Verify is a pilot program that was established in 1997, is generally voluntary, and remains in effect
today. Its purpose is to electronically confirm employment eligibility by using an employee’s I-9 form and confirming
with the Social Security Administration and Department of Homeland Security that the employee is allowed to work in
the United States. See, e.g., 8 U.S.C. § 1324a (note); 8 U.S.C. § 1324a(b)(3); About E-Verify, E-VERIFY (Apr. 10,
2018), https://www.e-verify.gov/about-e-verify. Federal employers, including federal contractors, must use E-Verify.
For all other employers, participation in E-Verify is optional. See 8 U.S.C. § 1324a (note) (referencing Secs. 402(a),
(e)); Exec. Order No. 13,465, 73 Fed. Reg. 33285 (June 11, 2008) (amending Exec. Order 12, 989, as amended).
81 See Whiting, 563 U.S. at 593–94.
82 See id. at 594; see also 8 U.S.C. § 1324a(h)(2).
83 See Whiting, 563 U.S. at 607.
84 Id.
85 Id. at 587.
86 Id. at 594.
87 8 U.S.C. § 1324a(h)(2).
88 See Whiting, 563 U.S. at 595, 600.
89 Id. at 596–99.
90 Id. at 599.
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Next, the Court held that the licensing provision was not impliedly preempted.91 The plaintiffs
argued that since Congress meant for the federal immigration system to be exclusive, “any state
system therefore necessarily conflicts with federal law.”92 The Court rejected this argument,
holding that Congress specifically carved out an exception for states in IRCA’s express
preemption clause and that Arizona ensured that LAWA tracked IRCA in all important aspects.93
The Court determined that LAWA sought to enforce only the ban on hiring unauthorized aliens
and that “Congress did not intend to prevent the States from using appropriate tools to exercise
that authority.”94
Finally, the Court held that LAWA’s requirement for all employers to use E-Verify was also not
impliedly preempted.95 The plaintiffs argued that this requirement impeded on Congress’s goal to
use a reliable and non-burdensome way to verify work authorization.96 The Court disagreed and
held that the mandatory use of E-Verify in Arizona did not conflict with federal objectives
because the provision in immigration law concerning E-Verify included no language to limit state
action.97 The Court further held that the law limited federal action only and that the federal
government had encouraged the use of E-Verify.98 The Court determined that Arizona’s use of EVerify did not obstruct Congress’s objectives to protect employee privacy, combat counterfeit
identity documents, and ensure reliability in employment verification.99
Arizona v. United States (2012)
In 2010, Arizona passed the Support Our Law Enforcement and Safe Neighborhoods Act,
commonly referred to as S.B. 1070.100 Before the law went into effect, the United States sued
Arizona and filed a motion for preliminary injunction.101 The United States argued that several
provisions of S.B. 1070 were preempted by federal law.102 The U.S. District Court for the District
of Arizona granted a preliminary injunction to enjoin four provisions of S.B. 1070, and the U.S.
Court of Appeals for the Ninth Circuit103 affirmed. The case was appealed to the Supreme
Court.104 In a 2012 majority opinion authored by Justice Kennedy, the Court recognized that the
United States “has broad, undoubted power over the subject of immigration” and that states “may
not pursue policies that undermine federal law.”105 The four provisions of S.B. 1070 at issue were
Sections 3, 5(C), 6, and 2(B), and the majority held that three of the four provisions were
preempted by federal law.
91 Id. at 607.
92 Id. at 600.
93 Id. at 600–01.
94 Id. at 601.
95 Id. at 608.
96 Id. at 607.
97 Id. at 608.
98 Id. at 608–09.
99 Id. at 609–10.
100 Arizona v. United States, 567 U.S. 387, 392–93 (2012).
101 Id. at 393–94.
102 Id. at 393.
103 For purposes of brevity, references to a particular circuit in this report (e.g., the Ninth Circuit) refer to the U.S.
Court of Appeals for that particular circuit (e.g., the U.S. Court of Appeals for the Ninth Circuit).
104 Arizona, 567 U.S. at 394.
105 Id. Justice Kagan took no part in the consideration or decision in this case. Id. at 416.
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The Court held that Section 3 of S.B. 1070, which made it a crime to fail to carry alien
registration documents in violation of federal law, was preempted because the United States had
already occupied the field of alien registration and that any state law that complements federal
law in this regard cannot stand, even if it is parallel.106 Additionally, according to the Court,
Section 3’s penalties were greater than and different from those imposed by federal law and
created a conflict with what Congress had already put in place regarding alien registration.107
The Court also held that Section 5(C), which made it a crime to work in Arizona without work
authorization, was preempted because Congress had already established parameters for work
authorization and chose to impose civil and criminal penalties on employers of unauthorized
aliens but only civil penalties on aliens who worked unlawfully in the United States.108 In the
Court’s view, Section 5(C) was standing as an obstacle to the federal regulatory system already in
place.109
Lastly, the Court determined that Section 6, which allowed a warrantless arrest if a state police
officer had probable cause to believe that the individual arrested committed a public offense that
made him or her removable from the United States, was preempted because it would give state
officers more power than federal immigration officers to arrest and detain people on the basis of
removability.110 By giving state officers the power to decide whether aliens should be arrested and
detained for being removable, Section 6 violated the principle “that the removal process is
entrusted to the discretion of the Federal Government.”111 Federal law provides very limited
circumstances in which a federal immigration officer can arrest a person without a warrant and
when a police officer can perform the function of a federal immigration officer.112 The Court
reasoned that Section 6 encroached on the federal government’s discretion to arrest aliens for
removal proceedings and served as an obstacle to this objective.113
The Court left intact the fourth provision, Section 2(B)—which required state officers to
determine “the immigration status of any person they stop, detain, or arrest” if there was
reasonable suspicion that the person was in the country without authorization and required that
anyone arrested would have his or her immigration status determined before being released.114
The Court held that because immigration laws encourage the sharing of information between
federal and state officers, nothing in Section 2(B) clearly indicated that it would be in violation of
federal law when applied.115 Furthermore, the Court observed that Section 2(B) contained
106 Id. at 400–03.
107 Id.; id. at 402 (“Were [Section 3] to come into force, the State would have the power to bring criminal charges
against individuals for violating a federal law even in circumstances where federal officials ... determine that
prosecution would frustrate federal policies.”)
108 Id. at 403–07.
109 Id.
110 Id. at 407–10.
111 Id.
112 Id.; see also 8 U.S.C. § 1357(a)(2) (detailing how without a warrant, a federal immigration officer can arrest a
person if he or she believes that the person is “in the United States in violation of any [immigration] law or regulation”
but only where the person “is likely to escape before a warrant can be obtained”); 8 U.S.C. § 1357(g) (detailing how
police officers can perform certain functions of a federal immigration officer when they enter into formal agreements
with the federal government).
113 See Arizona, 567 U.S. at 407–10.
114 See id. at 411 (internal quotation marks omitted).
115 Id. at 411–15 (internal quotation marks omitted).
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limitations to prevent it from conflicting with federal immigration law.116 The federal government
contended that even with these limitations, the provision still created an obstacle to Congress’s
framework, specifically regarding mandatory immigration status checks and prolonged detention
while the checks were taking place.117 The Court rejected these contentions and stated that
“Congress has made clear that no formal agreement ... needs to be in place for state officers to
communicate with” federal immigration officers regarding an individual’s immigration status,
and federal law “leaves room for a policy requiring state officials to contact [U.S. Immigration
and Customs Enforcement] as a routine matter.”118 The Court also explained that at this point, it
was not clear whether Section 2(B) would lead to prolonged detention of an individual, because if
the law requires state officers to determine the immigration status during the course of a lawful
detention, the provision could survive preemption “absent some showing that it has consequences
that are adverse to federal law and its objectives.”119
Justice Scalia wrote a separate opinion, concurring in part and dissenting in part.120 He began by
arguing that the states have a “sovereign interest in protecting their borders” and that, “as a
sovereign, Arizona has the inherent power to exclude persons from its territory, subject only to
those limitations expressed in the Constitution or constitutionally imposed by Congress.”121 In
support of his assertion that, as sovereigns, states have the authority to prevent the influx of
individuals, Justice Scalia cited, among other things, the Compact Clause of the Constitution,
which provides that “[n]o State shall, without the Consent of Congress ... engage in War, unless
actually invaded, or in such imminent Danger as will not admit of delay.”122 He acknowledged
that although this clause limits a state’s sovereignty in ways not relevant to the discussion of the
case, “it leaves intact [its] inherent power to protect [its] territory.”123 Justice Scalia pointed out
that Arizona had every right to exclude people from its state who have no right to be in the United
States.124 He argued that Arizona was simply trying to enforce already existing immigration
restrictions more effectively and that, if the state cannot even do that, then it should no longer be
considered a sovereign state.125 Justice Scalia also believed that, in exercising its sovereign
authority, Arizona could impose harsher penalties than federal law could for violations of its own
law.126
With respect to S.B. 1070’s provisions at issue, Justice Scalia maintained that Section 3 “merely
ma[de] a violation of state law the very same failure to register and failure to carry evidence of
116 Id. at 411 (describing the three limits as follows: (1) a detained person is not presumed to be an alien who is
unlawfully present if he or she can show “a valid Arizona’s driver’s license or similar identification”; (2) police officers
are not allowed to consider a person’s race or national origin except as permitted under the U.S. and state constitutions;
and (3) the provision of S.B. 1070 must be implemented in a way that protects the civil rights of all people, respects
“the privileges and immunities of United States citizens,” and is consistent with federal law).
117 Id. at 411.
118 Id. at 411–13.
119 Id. at 413–14; see also id. at 414 (“There is no need in this case to address whether reasonable suspicion of illegal
entry or another immigration crime would be a legitimate basis for prolonging detention, or whether this too would be
preempted by federal law.”); cf. (“This opinion does not foreclose other preemption and constitutional challenges to the
law as interpreted and applies after it goes into effect.”).
120 Justice Scalia concurred with the majority only on Section 2(B). Id. at 416 (Scalia, J., concurring in part and
dissenting in part).
121 Id. at 417 (Scalia, J., concurring in part and dissenting in part).
122 Id. at 419, 424 (Scalia, J., concurring in part and dissenting in part); U.S. CONST. art. I, § 10, cl. 3.
123 Arizona, 567 U.S. at 419 (Scalia, J., concurring in part and dissenting in part).
124 Id. at 417 (Scalia, J., concurring in part and dissenting in part).
125 Id. at 437 (Scalia, J., concurring in part and dissenting in part).
126 Id. at 430 (Scalia, J., concurring in part and dissenting in part).
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registration that are violations of federal law [and] ... Arizona’s legitimate interest in protecting ...
its unemployment-benefits system is an entirely adequate basis” for enacting this law.127 For
Section 5, he believed that the fact that Congress chose not to impose criminal penalties for
unauthorized work does not mean the states are prohibited from imposing their own criminal
penalties.128 For Section 6, he argued that Arizona can have its own immigration policy so long as
it is not in conflict with federal law and that the executive branch’s “policy choice of lax federal
enforcement” is not a valid federal prohibition to stop Arizona from protecting its borders.129
Finally, Justice Scalia agreed with the Court’s rejection of the government’s challenge to Section
2(B).130
Justice Thomas also wrote a separate opinion, concurring in part and dissenting in part. He agreed
with Justice Scalia that none of the provisions of S.B. 1070 at issue was preempted by federal
immigration law but reached that conclusion because he determined that there was no conflict
“between the ordinary meaning of the relevant federal laws and that of the four provisions of”
S.B. 1070.131 He also disagreed with the Court’s holding that “Congress preempted the field of”
alien federal registration because “nothing in the text of the relevant federal statutes indicates that
Congress intended enforcement of its registration requirements to be exclusively the province of
the Federal Government.”132 Further, according to him, the alien registration system that Congress
created shows that it could work on its own, not that Congress “wanted to preclude the [s]tates
from enforcing the federal standards.”133 Finally, he emphasized that the “‘purposes and
objectives’ theory of implied preemption is inconsistent with the Constitution because it invites
courts to engage in freewheeling speculation about congressional purpose that roams well beyond
statutory text” and that, under the Supremacy Clause, preemption should apply to
“congressionally enacted laws, not to judicially divined legislative purposes.”134
Justice Alito wrote a separate opinion as well, concurring in part and dissenting in part. He agreed
with the majority that Section 2(B) was not preempted and that Section 3 was preempted.135
However, he further argued that Sections 5(C) and 6 were not preempted by federal law.136
According to Justice Alito, the majority’s holding regarding Section 5(C) was at odds with De
Canas v. Bica. Even though federal regulation in the employment of aliens is much more
pervasive today (due to IRCA’s passage) since De Canas, Justice Alito asserted that the Court still
had “to determine whether the federal scheme discloses a clear and manifest congressional intent
to displace state law.”137 Congress, according to Justice Alito, clearly “chose not to impose
federal criminal penalties” on aliens who work without authorization, but this “does not mean
that Congress also chose to preempt state criminal penalties.”138 Justice Alito maintained that
because an inference could be made for or against preemption, federal law had not clearly or
manifestly displaced state law in this space and therefore, Section 5(C) was not preempted by
127 Id. at 429–30 (Scalia, J., concurring in part and dissenting in part).
128 Id. at 432 (Scalia, J., concurring in part and dissenting in part).
129 Id. at 427–28 (Scalia, J., concurring in part and dissenting in part).
130 Id. at 425 (Scalia, J., concurring in part and dissenting in part).
131 Id. at 437 (Thomas, J., concurring in part and dissenting in part) (internal quotation marks omitted).
132 Id. at 438–39 (Thomas, J., concurring in part and dissenting in part).
133 Id. at 439 (Thomas, J., concurring in part and dissenting in part).
134 Id. at 440 (Thomas, J., concurring in part and dissenting in part) (internal quotation marks omitted).
135 Id. at 441 (Alito, J., concurring in part and dissenting in part).
136 Id.
137 Id. at 451 (Alito, J., concurring in part and dissenting in part).
138 Id. at 452 (Alito, J., concurring in part and dissenting in part).
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federal law.139 Justice Alito then determined that Section 6 was also not preempted because it
“adds little to the authority that Arizona officers already possess, and whatever additional
authority it confers is consistent with federal law.”140 Justice Alito further determined that there
were several ways to enforce Section 6, and the majority’s invalidation of the statute without first
seeing if Arizona implemented it in a way contrary to congressional intent had been premature.141
The Arizona opinion informed subsequent litigation in lower courts. For example, reviewing
courts applied Arizona to hold that state laws similar to S.B. 1070 were preempted.142 Yet
reviewing courts reached different conclusions about how Arizona and other Supreme Court
rulings applied to other types of immigration-related measures, such as restrictions on unlawfully
present aliens’ ability to rent housing.143 Further, according to at least one scholar, the Arizona
opinion used a methodology in its preemption analysis that had not been used before: Instead of
relying solely on specific statutes in the INA, the majority also relied on the executive branch’s
assertions regarding its enforcement priorities that existed at the time.144 Justice Alito criticized
the government’s position and explained that the enforcement priorities are policy rather than law
and posed the rhetorical question of whether a preempted state statute could be un-preempted in
the future if the executive branch were to change its enforcement priorities.145 He also argued that
the majority opinion gave “short shrift” to the Court’s presumption against preemption.146 Justice
Alito later had an opportunity to further this line of analysis when he authored the majority
opinion in Kansas v. Garcia.
139 Id. at 453 (Alito, J., concurring in part and dissenting in part).
140 Id. at 454 (Alito, J., concurring in part and dissenting in part).
141 Id. at 458 (Alito, J., concurring in part and dissenting in part).
142 See e.g., Georgia Latino All. for Hum. Rts. v. Governor of Georgia, 691 F.3d 1250 (11th Cir. 2012); Hisp. Int. Coal.
of Alabama v. Governor of Alabama, 691 F.3d 1236 (11th Cir. 2012); United States v. South Carolina, 720 F.3d 518
(4th Cir. 2013).
143 See e.g., Villas at Parkside Partners v. City of Farmers Branch, 726 F.3d 524 (5th Cir. 2013) (holding that an
ordinance that prevented rental housing to unlawfully present individuals was preempted because, among other things,
by creating criminal offense provisions it disrupted the existing federal immigration framework and covered more
unlawful conduct than the existing federal anti-harboring statute did); Keller v. City of Fremont, 719 F.3d 931 (8th Cir.
2013) (holding that an ordinance that prevented rental housing to unlawfully present individuals was not preempted
because, among other things, it did not physically remove anyone from the city and immigration officials still had full
discretion in deciding when and whether to pursue removal proceedings); Lozano v. City of Hazleton, 724 F.3d 297 (3d
Cir. 2013) (holding that ordinances that prevented rental housing to unlawfully present individuals and regulated
employment of individuals without work authorization were preempted because, among other things, they applied to a
wider group of people than currently existed under federal immigration law and interfered “with the federal
government’s discretion” over the removal process).
144 See Pratheepan Gulasekaram, Immigration Enforcement Preemption, 84 OHIO ST. L.J. 535, 537 (2023); see also
Arizona, 567 U.S. at 396 (“A principal feature of the removal system is the broad discretion exercised by immigration
officials.... Discretion in the enforcement of immigration law embraces immediate human concerns.”); see id. at 402
(stating that if Section 3 of S.B. 1070 were in effect, Arizona could “bring criminal charges against individuals for
violating a federal law in circumstances where federal officials in charge of the comprehensive scheme determine that
prosecution would frustrate federal policies”); id. at 409 (“By authorizing state officers to decide whether an alien
should be detained for being removable, [Section 6 of S.B. 1070] violates the principle that the removal process is
entrusted to the discretion of the Federal Government.”). Contra Gulasekaram, supra note 14, at 554–55 (“In [De
Canas v. Bica] ... federal enforcement practices seemed to play little ... role, at least in so far as explicit references to
presidential priorities or practices.... [T]he background statutory scheme was not designed for any federal enforcement
of unauthorized employment; thus the President could not help define the limits of federal workplace enforcement
policy.”).
145 See Arizona, 567 U.S. at 445 (Alito, J., concurring in part and dissenting in part).
146 Id. at 451.
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Kansas v. Garcia (2020)
In 2017, the Kansas Supreme Court in three separate cases reversed the convictions of three
unlawfully present aliens for state identity theft and false information. The state court held that a
provision in IRCA expressly preempted the state statutes at issue insofar as they related to those
prosecutions.147 The state identity theft statute criminalized “the ‘using’ of ‘any personal
identifying information’ belonging to another person with the intent to ‘defraud that person or
anyone else’” to receive a benefit.148 The state false information statute criminalized “‘making,
generating, distributing or drawing’ a ‘written instrument’ with knowledge that it ‘falsely states or
represents some material matter’ and ‘with intent to defraud, obstruct the detection of a theft or
felony offense or induce official action.’”149 The respondents had used stolen Social Security
numbers on their I-9 and W-4 forms when they were applying for jobs and had been convicted of
either or both of these state statutes.150 IRCA makes it unlawful to hire unauthorized aliens and
states that the I-9 form “and any information contained in or appended ... may not be used for
purposes other than for enforcement of” certain sections of the INA.151 The respondents argued
that the Kansas statutes had to defer to federal law when it came to using the information on the I9 for something other than securing employment (i.e., their prosecutions).152
The cases were appealed to the U.S. Supreme Court, where the issue before the Court was
whether the Kansas statutes were expressly or impliedly preempted by IRCA.153 In 2020, Justice
Alito, writing for the majority, reversed the judgments of the Kansas Supreme Court and held that
the statutes were not preempted.154 All nine justices155 first rejected the argument that the state’s
statutes were expressly preempted by IRCA because the language in 8 U.S.C. § 1324a(b)(5),
which generally limits use of the I-9, could not be read so broadly as to prevent any entity or
person from ever using any information on an I-9—including things like a telephone number or
an email address—outside of the narrow situations listed in the statute.156
The Court then considered whether the statutes were impliedly preempted. The Court first held
that the statutes were not field preempted because IRCA did not bar states from the entire field of
employment verification.157 Further, the Court explained that the federal employment verification
system under IRCA is meant to prevent unauthorized aliens from being hired, whereas the
purpose of using tax-withholding forms is to enforce tax laws.158 The Court held that using
someone else’s “Social Security number on tax forms” creates harm—related to wages and
certain benefits such as disability or retirement—that is unrelated to immigration law.159 Next, the
147 Kansas v. Garcia, 589 U.S. 191, 201 (2020).
148 Id. at 198.
149 Id.
150 Id. at 198–200. The Form W-4 is used so an employer can determine the right amount of federal income tax to
withhold from an employee’s pay. See About Form W-4, Employee’s Withholding Certificate, Internal Revenue
Service, https://www.irs.gov/forms-pubs/about-form-w-4 (last visited Apr. 30, 2025).
151 8 U.S.C. § 1324a(b)(5).
152 Kansas, 589 U.S. at 203.
153 Id.
154 Id. at 195.
155 See id. at 207; see also id. at 213 (Thomas, J., concurring; Gorsuch, J., concurring), 215 (Breyer, J., Ginsburg, J.,
Sotomayor, J., and Kagan, J. concurring in part and dissenting in part).
156 Id. at 203–07.
157 Id. at 210.
158 Id. at 208–09.
159 Id. at 209.
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Court held that the statutes were not conflict preempted because it is possible to comply with the
state statutes and IRCA and that the fact that there is overlap between state and federal statutes
does not necessarily mean there is conflict.160 The Court distinguished its opinion in Arizona—
where the majority held that Congress made a concerted effort not to prosecute people working in
the United States without authorization—and held that IRCA made no concerted effort not to
criminalize conduct relating to the use of false identity documents on tax forms.161 The Court
further explained that the Kansas statutes did not frustrate federal interests and that the federal
government fully supported Kansas’s decision to prosecute the respondents.162 Lastly, the Court
determined that a disruption in federal priorities by state prosecutions does not signal the
existence of preemption, because the Supremacy Clause prioritizes “‘the Laws of the United
States’” and “not the criminal law enforcement priorities or preferences of federal officers.”163
Justice Thomas, joined by Justice Gorsuch, wrote a separate concurring opinion, reiterating the
view that the Court should explicitly abandon the “purposes and objectives preemption
jurisprudence.”164 This jurisprudence, according to Justice Thomas, “rests on judicial guesswork
about ‘broad federal policy objectives, legislative history, or generalized notions of congressional
purposes that are not contained within the text of federal law.’”165 Instead, Justice Thomas
asserted that a proper interpretation of the Supremacy Clause requires ascertaining “whether the
ordinary meaning of federal and state law ‘directly conflict’” and that preemption exists only if
there is a logical contradiction between federal and state law.166
Justice Breyer, joined by Justices Ginsburg, Sotomayor, and Kagan, filed a separate opinion,
concurring in part and dissenting in part.167 Justice Breyer explained that he agreed that IRCA
does not expressly preempt the Kansas statutes but disagreed with the majority’s opinion over
implied preemption.168 According to Justice Breyer, IRCA, through its comprehensive scheme,
clearly and manifestly showed that “Congress has occupied at least the narrow field of policing
fraud committed to demonstrate federal work authorization.”169 Justice Breyer characterized the
statute as containing very detailed requirements to fight employment of unauthorized aliens,
including two “calibrated sets of sanctions for noncompliance”: one for employers and one for
employees.170 Justice Breyer further explained that for employers, IRCA imposes federal
penalties for hiring unauthorized aliens,171 and for employees, IRCA imposes federal penalties
only “for anyone [who commits] fraud ‘for the purpose of satisfying’ [IRCA’s] requirements.”172
Further, according to Justice Breyer, even though IRCA’s goal is to combat the employment of
160 Id. at 211.
161 Id. at 212.
162 Id.
163 Id.
164 Id. at 213–15 (Thomas, J., concurring; Gorsuch, J., concurring). Justice Thomas first brought up the argument that
the Court should explicitly abandon this jurisprudence in Wyeth v. Levine. See 555 U.S. 555, 604 (2009) (Thomas, J.,
concurring). He brought it up again in Arizona v. United States. See 567 U.S. 387, 440 (2012) (Thomas, J., concurring
in part and dissenting in part).
165 Kansas, 589 U.S. at 214 (Thomas, J., concurring; Gorsuch, J., concurring).
166 Id.
167 Id. at 215 (Breyer, J., Ginsburg, J., Sotomayor, J., and Kagan, J., concurring in part and dissenting in part).
168 Id.
169 Id.
170 Id. at 216 (Breyer, J., Ginsburg, J., Sotomayor, J., and Kagan, J., concurring in part and dissenting in part).
171 Id. (citing 8 U.S.C. § 1324a).
172 Id. at 217 (Breyer, J., Ginsburg, J., Sotomayor, J., and Kagan, J., concurring in part and dissenting in part) (quoting
18 U.S.C. § 1546(b)).
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unauthorized aliens, it does not pursue this goal by any and all means, because the statute
generally imposes criminal penalties on the employers only and not on the unauthorized alien
employees themselves who merely seek such employment.173 Lastly, Justice Breyer asserted that
IRCA clearly allows only the federal government to punish conduct related to fraudulently
demonstrating federal work authorization and not the states, such as Kansas.174 According to him,
among other things, Kansas prosecuted an unauthorized alien “for misrepresenting ... federal
work-authorization status for the purpose of obtaining employment ... and fell squarely within the
field that ... [IRCA] preempts.”175
Legal scholars have noted that in the Kansas decision, Justice Alito was able to continue the
discussion he began in his concurring and dissenting opinion in Arizona about whether the
executive branch’s immigration policies at a particular point in time should or should not guide a
court’s preemption analysis, especially when the party bringing the lawsuit does not identify a
specific federal statute that preempts state law.176 In Arizona, Justice Alito criticized the
majority’s reliance on the executive branch’s immigration enforcement priorities and explained
that the priorities were not law and therefore should not have been relied upon in the preemption
analysis.177 Less than a decade later in Kansas, the majority (which Justice Alito authored) held
that “[t]he Supremacy Clause gives priority to ‘the laws of the United States,’ not the criminal
law enforcement priorities or preferences of federal officers.”178 In Kansas, Justice Alito seemed
to repudiate the reliance on the executive branch’s immigration policies or priorities as a basis for
the preemption analysis (which was present in Arizona) and “normalize the presence of states in
immigration enforcement matters.”179 As the executive branch’s immigration priorities
continually change with different Administrations, states that have been dissatisfied with the
federal government’s handling of immigration enforcement have recently relied on Justice
Scalia’s partial dissent in Arizona—where he explained that states have a “sovereign interest in
protecting their borders”—to pass legislation that seeks to deter the presence of unlawfully
present aliens and normalize a state’s involvement in immigration enforcement matters.180
Preemption and Immigration: Select Cases Pending
in Lower Courts
New litigation has emerged in the past year or so as a result of several states passing legislation to
deter the presence of unlawfully present aliens within their borders. Specifically, several states
have recently enacted laws that criminalize the presence of individuals in their states who have
either unlawfully entered or reentered into the United States.181 In addition, this legislation allows
173 Id.
174
Id. at 218–20 (Breyer, J., Ginsburg, J., Sotomayor, J., and Kagan, J., concurring in part and dissenting in part).
175 Id. at 220 (Breyer, J., Ginsburg, J., Sotomayor, J., and Kagan, J., concurring in part and dissenting in part).
176 See Gulasekaram, supra note 144, at 539 (“The migration from Arizona to Kansas resurfaces profound separation of
powers and federalism debates raising difficult questions about the role of the President in defining federal policy vis a
vis both Congress and the states.”).
177 See Arizona, 567 U.S. at 445 (Alito, J., concurring in part and dissenting in part).
178 See Kansas, 589 U.S. at 212.
179 See Gulasekaram, supra note 144, at 567.
180 See Arizona, 567 U.S. at 417 (Scalia, J., concurring in part and dissenting in part).
181 See, e.g., United States v. Texas, 97 F.4th 268 (5th Cir. 2024).
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for state judges to order an alien’s removal.182 The plaintiffs in these cases argue that these laws
are field and conflict preempted.183
The ensuing litigation in the various states may provide an opportunity for the Supreme Court to
revisit its preemption jurisprudence. This section begins by summarizing Texas v. United States—
commonly known as the Texas S.B. 4 case. The section continues by summarizing pending
litigation in other states that enacted laws similar to Texas.
Texas, S.B. 4 (United States v. Texas)
In November 2023, Texas passed Senate Bill 4 or S.B. 4, making it a crime, among other things,
to “enter[] or attempt[] to enter this state directly from a foreign nation at any location other than
a lawful port of entry.”184 The law was set to become effective on March 5, 2024.185 Under S.B. 4,
entering the United States outside a port of entry and into Texas would be a violation of federal
law under 8 U.S.C. §§ 1325 and 1326 and a violation of Texas state law. Section 1325 generally
makes it a criminal offense to improperly enter or attempt to enter the United States, while
Section 1326 makes it a federal crime for a previously removed alien to reenter the United States
without authorization.186 Aliens who violate these federal statutes may be subject to criminal
penalties, including imprisonment, and civil fines.187
S.B. 4 has several provisions, but four of them are the subject of litigation where preemption
challenges have been raised. The first provision makes it a state crime for aliens to enter Texas
anywhere other than at lawful ports of entry.188 Under S.B. 4, a violation of this provision is a
misdemeanor and carries a fine of up to $2,000 and/or imprisonment of up to 180 days.189 The
second provision makes it a crime for aliens to reenter Texas after being removed or ordered
removed from the United States.190 A violation of this Texas provision is a misdemeanor and
carries a fine of up to $4,000 and/or imprisonment of up to one year.191 The third provision
authorizes state judges and magistrate judges to order the removal of an alien back to “the foreign
nation from which the person entered or attempted to enter.”192 This third provision applies any
time an alien is convicted of either of the first two provisions.193 Finally, the fourth provision
prevents state judges from abating prosecutions “on the basis that a federal determination
regarding the immigration status of the defendant is pending or will be initiated.”194
182 See, e.g., United States v. Iowa, 126 F.4th 1334 (8th Cir. 2025), vacated, No. 24-2265, 2025 WL 1140834, at *1
(8th Cir. Apr. 15, 2025).
183 See, e.g., United States v. Oklahoma, 739 F. Supp. 3d 985 (W.D. Okla. 2024).
184 S.B. 4, 88th Leg., 4th Spec. Sess. (Tex. 2023),
https://capitol.texas.gov/tlodocs/884/billtext/pdf/SB00004F.pdf#navpanes=0.
185 See United States v. Texas, 719 F. Supp. 3d 640, 658 (W.D. Tex. 2024).
186 For a more detailed review on the federal immigration crimes of illegal entry and reentry, see this CRS Report
R47667, Immigration Crimes: Improper Entry and Reentry, by Kelsey Y. Santamaria (2023).
187 See 8 U.S.C. §§ 1325, 1326.
188 TEX. PENAL CODE ANN. § 51.02.
189 Id. § 51.02(b); § 12.22.
190 TEX. PENAL CODE ANN. § 51.03.
191 Id. § 51.03(b); § 12.21.
192 TEX. CODE CRIM. PROC. ANN. art. 5B.002 (West 2024).
193 Id.
194 TEX. CODE CRIM. PROC. ANN. art. 5B.003 (West 2024).
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In December 2023 and January 2024, a group of plaintiffs filed two different complaints and
motions for a preliminary injunction against Texas, arguing that S.B. 4 violates the Supremacy
Clause of the U.S. Constitution because it is field and conflict preempted.195 A judge in the
District Court for the Western District of Texas consolidated the cases on January 31, 2024.196
The parties cited Arizona v. United States in their motions to the court, comparing and contrasting
S.B. 4 to Arizona’s S.B. 1070.197 The plaintiffs argued that S.B. 4 is field preempted because “it
regulates a field—entry and removal of noncitizens—that Congress has committed to the federal
government’s ‘exclusive governance.’”198 The plaintiffs emphasized that it is the United States,
and not the states, that have broad, undoubted power over immigration and that not only does
S.B. 4 regulate alien entry, reentry, and removal, it “also directly implicates the United States’
foreign relations.”199 By criminalizing actions that take place on the southern border and
regulating immigration functions, the plaintiffs argue, S.B. 4 is trampling over federal interests.200
Finally, the plaintiffs pointed out that since Arizona v. United States, lower courts “have routinely
held that state immigration crimes paralleling their federal counterparts are field preempted.”201
The plaintiffs then argued that S.B. 4 is conflict preempted because it allows the state to remove
people whose right to remain in the country could be under review by federal immigration
officials, it conflicts with the federal government’s ability to determine where aliens can be
removed to by working with foreign governments, its punishments are broader than federal law
allows, and it intrudes on the ways in which Congress has determined under what limited
circumstances state officers can help with immigration enforcement.202
Texas argued that S.B. 4 comports with federal law and can therefore not be conflict
preempted.203 Texas also argued that although S.B. 4 might be an obstacle to the executive
branch’s objectives, it is not an obstacle to Congress’s objectives and emphasized that Supremacy
Clause jurisprudence focuses on federal laws rather than executive priorities in their
implementation.204 Texas then argued that S.B. 4 is not field preempted because, among other
things, states have wide latitude in regulating misconduct of aliens and others within their
jurisdictions and that, even if the removal of aliens is exclusively a federal power, S.B. 4 does not
actually remove anyone from the United States.205 Further, even if field preemption remains a
viable argument, Texas argued, there can be no field preemption when “the federal executive
branch has abandoned the very field it now purports to occupy.”206 Finally, Texas argued that even
195 Complaint for Declaratory and Injunctive Relief, Las Americas Immigrant Advoc. Ctr. v. Texas, No. 1:23-cv-1537
(W.D. Tex. Dec. 19, 2023), Dkt. No. 1; Complaint, United States v. Texas, 719 F. Supp. 3d 640 (W.D. Tex. 2024)
(No. 1:24-cv-00008), Dkt. No. 1.
196 Order, United States v. Texas, 719 F. Supp. 3d 640 (W.D. Tex. 2024) (No. 1:24-cv-00008-DAE), Dkt. No. 45.
197 See generally United States’ Motion for Preliminary and Permanent Injunction at 14–21, 24–26, 30–31, United
States v. Texas, 719 F. Supp. 3d 640 (W.D. Tex. 2024) (No. 1:24-cv-00008-RP), Dkt. No. 14 [hereinafter Plaintiffs’
Motion]; Defendants’ Consolidated Response in Opposition to Plaintiffs’ Motions for Preliminary Injunction at 15–18,
21, 30, United States v. Texas, 719 F. Supp. 3d 640 (W.D. Tex. 2024) (No. 1:24-cv-00008-DAE), Dkt. No. 25
[hereinafter Defendants’ Response].
198 See Plaintiffs’ Motion, supra note 197, at 14.
199 Id. at 15.
200 Id. at 16–17.
201 Id. at 20.
202 See id. at 22–25.
203 See Defendants’ Response, supra note 197, at 12–13.
204 See id. at 14 (referring to the Biden Administration’s objectives as “favor[ing] open-border policies”).
205 See id. at 15–16.
206 Id. at 19–20.
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if federal immigration laws preempt S.B. 4, the federal government’s duty to protect the states
and the state’s constitutional right to defend itself are not diminished if there is an “invasion at the
border.”207 This determination, according to Texas, rebuts the plaintiffs’ preemption claims.208
According to Texas, the United States failed to protect the state and its citizens by allowing
individuals to enter Texas without authorization—including cartel members who traffic weapons,
drugs, and people—so this amounts to an “invasion at the border.”209 Texas relied at least in part
on Justice Scalia’s partial dissent in Arizona and argued that it has the same constitutional right to
defend itself from an “invasion at the border” that the United States does.210
On February 29, 2024, just days before S.B. 4 was set to become effective, the district court
granted a preliminary injunction blocking S.B. 4 from taking effect.211 The court held that S.B. 4
was field and conflict preempted.212 The court spent the majority of its analysis on field
preemption. First, the court held that the field of immigration is so deeply intertwined with the
federal government’s foreign relations and that the federal government has an interest in
admitting and removing aliens.213 Second, the court held that there is no “question that the federal
government occupies the field of immigration,” as there are countless federal immigration
statutes and treaties that support this statement, and that Congress has made it clear there is no
room for states to supplement this existing framework.214 Third, the court relied on the Supreme
Court’s analysis in Arizona v. United States and held that two sections of S.B. 4 that try to “vest a
state with the power to punish federal immigration offenses” are strikingly similar to S.B. 1070
(the law in question in Arizona) and the majority in Arizona forbade this type of concurrent
criminalization.215 Fourth, the court held that “[b]y authorizing state officials to conduct removals
... [S.B. 4] intrudes into a particularly sensitive area of foreign affairs and is field preempted.”216
The court also dispelled some of Texas’s arguments against field preemption by holding that field
preemption is not limited to alien registration; orders under S.B. 4 really are removal orders and
these types of decisions must be made by the federal government alone; state laws, like S.B. 4,
that run concurrent to federal law run the risk of preemption because Congress has stated that
“federal statutes are the sole and exclusive procedure for determining” alien admissibility and
removability; and just because Texas is unhappy with the former Biden Administration’s handling
of immigration enforcement does not mean that there can be no field preemption and that “the
federal government has abandoned the role of immigration enforcement.”217
207 See id. at 22–31 (citing to and quoting the Compact Clause and Guarantee Clause of the Constitution). The
Guarantee Clause of the Constitution states, “The United States shall guarantee every State ... a Republican form of
Government, and shall protect each of them against Invasion.” U.S. CONST. art. IV, § 4 (emphasis added).
208 See Defendants’ Response, supra note 197, at 29 (“Texas’s sovereign right of self-defense, as reserved to the States
in Article I, Section 10, Clause 3, independently forecloses Plaintiffs’ preemption claims against SB4.”).
209 See id. at 25–26.
210 See id. at 24–25.
211 United States v. Texas, 719 F. Supp. 3d 640, 682 (W.D. Tex. 2024).
212 Id. at 674.
213 Id. at 663–65; see also id. at 665 (“Texas’s own state courts acknowledge the matter of entry into the United States
is wholly preempted by federal law as are matters involving deportation.” (internal citation and quotation marks
omitted)).
214 Id. at 665–66; see id. at 666 (reaffirming the notion that Congress occupies the field of removal, as evidenced
through the INA).
215 Id. at 666–67.
216 Id. at 668.
217 Id. at 668–74.
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For conflict preemption, the district court relied again on Arizona and held that S.B. 4 gives state
officers “the power to enforce federal law without supervision” and is conflict preempted because
Congress already created a way in which the enforcement of “federal immigration law is
conducted under the watch of federal officials in a uniform way across all 50 states.”218 In
addition, the court held that S.B. 4 takes away federal immigration officers’ discretion in the
enforcement of immigration law, instructs “judges to disregard pending federal defenses,”
removes all aliens to Mexico in contradiction to federal immigration law that requires
consideration of various factors, and exceeds penalties that currently exist under federal
immigration law.219 Finally, the court addressed Texas’s “invasion” argument and held that
unlawful immigration is not considered an “invasion” under the U.S. Constitution,220 enacting
S.B. 4 Texas is not a wartime response,221 and even if Texas were at war it would have to “cede
authority to the federal government to conduct that war once the federal government has had time
to respond to the purported invasion.”222 According to the court, “Texas either is engaging in war,
in which case it must obey federal war directives once the federal military has responded, or it is
not engaging in war, in which case the [Compact Clause] does not apply.”223
Texas appealed the case and, on March 2, 2024, the Fifth Circuit stayed the district court’s
preliminary injunction.224 On March 4, 2024, the Supreme Court stayed the Fifth Circuit’s
order,225 and on March 19, 2024, the Court declined to vacate the Fifth Circuit’s stay of the
preliminary injunction.226 Also on March 19, 2024, the Fifth Circuit lifted its own administrative
hold,227 and the next day, the Fifth Circuit heard oral arguments on the stay against the district
court’s injunction.228 On March 26, 2024, in an interlocutory229 decision, the Fifth Circuit denied
Texas’s motion to stay the injunction pending appeal before the court.230 “On a motion for a stay
pending appeal,” a court considers four factors as set forth by the Supreme Court in Nken v.
Holder.231 The Fifth Circuit largely focused its analysis on the first factor—likeliness of success
on the merits—and held that Texas failed to show that it would succeed on the merits of the
plaintiffs’ preemption claims and that there is sufficient authority to support the claim that S.B. 4
218 Id. at 674.
219 Id. at 674–77.
220 Id. at 680–89.
221 Id. at 689–90; see id. at 689 (“None of [S.B. 4’s] provisions are operations of war. Rather, they are standard
operations of criminal enforcement by state civil authorities.”).
222 Id. at 690–94; see id. at 691 (“Here, the United States has had time to respond, and it has directed Texas to halt
enforcement of SB4. If the United States is truly at war, Texas may not direct its officers to disobey that command.”
(internal citation omitted)).
223 Id. at 694.
224 United States v. Texas, No. 24-50149, 2024 WL 909612 (5th Cir. Mar. 2, 2024).
225 United States v. Texas, No. 23A814, 2024 WL 909451 (Mem) (U.S. Mar. 4, 2024). On March 12, United States v.
Texas, No. 23A814, 2024 WL 1055544 (Mem) (U.S. Mar. 12, 2024), and on March 18, 2024, United States v. Texas,
No. 23A814, 2024 WL 1151565 (Mem) (U.S. Mar. 18, 2024), the Supreme Court extended its hold.
226 United States v. Texas, 144 S. Ct. 797 (2024).
227 United States v. Texas, 96 F.4th 797 (5th Cir. 2024).
228 United States v. Texas, 97 F.4th 268, 274 (5th Cir. 2024).
229 An interlocutory decision is a decision “that relates to some intermediate matter in the case; any order other than a
final order.” See Order, BLACK’S LAW DICTIONARY (12th ed. 2024).
230 United States v. Texas, 97 F.4th 268 (5th Cir. 2024).
231 Id. at 274. The four factors are “(1) whether the stay applicant has made a strong showing that he is likely to succeed
on the merits; (2) whether the applicant will be irreparably injured absent a stay; (3) whether issuance of the stay will
substantially injure other parties ... and (4) where the public interest lies.” Id. (quoting Nken v. Holder, 556 U.S. 418,
426 (2009)).
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is field or conflict preempted.232 The Fifth Circuit was also not convinced that the Compact
Clause, or Texas’s “invasion at the border” argument, could compel a different result.233
The Fifth Circuit’s opinion spanned 121 pages. For field preemption, the Fifth Circuit held that
S.B. 4’s provision on removal likely encroaches on the field of immigration removal by giving
state judges authority that is reserved only for the United States and that Texas failed to
demonstrate that it is likely to prevail on its argument that the district court erred by holding that
S.B. 4 is likely field preempted.234 The Fifth Circuit further held that giving the state this
authority precludes aliens from being able to avail themselves “of rights [they have] under federal
law.”235 For conflict preemption, the Fifth Circuit held that S.B. 4 likely conflicts with the federal
government’s exercise of discretion in deciding whether to initiate civil or criminal proceedings
when an alien is arrested, because in Texas, an alien is arrested and charged with the crime of
illegal entry (or reentry) and the federal government has no say in the matter.236 The Fifth Circuit
held that S.B. 4 also likely conflicts with federal immigration law because it authorizes state
judges to remove aliens from the United States without the federal government’s consent, takes
away “the United States’ authority to select the country to which [aliens] will be removed,” and
takes away the federal government’s discretion in deciding who it will allow to stay in the United
States.237 Finally, the Fifth Circuit briefly mentioned Texas’s “invasion at the border” argument
and held that because Texas provided no authority to support its claim, Texas failed to persuade
that it would likely prevail on the merits of this argument.238
Judge Oldham wrote a separate dissenting opinion, focusing his analysis on the section of S.B. 4
that criminalizes illegal entry, and concluded that this section is not field or conflict preempted.239
For field preemption, he argued that Congress has the exclusive power in determining who can
enter the country and under what conditions but that this section does not affect whom Congress
allows to enter the United States and says only that Texas is allowed to arrest people who “cross
the border somewhere other than a lawful port of entry.”240 Judge Oldham also argued that for
Supremacy Clause arguments, what matters is what the laws of the United States say and not
“criminal law enforcement priorities or preferences of federal officers.”241 Next, Judge Oldham
did not believe that a court should “infer that Congress has occupied a field whenever it
proscribes something” and instead reminded that just because a state and federal law overlap does
not mean preemption automatically exists.242 For conflict preemption, Judge Oldham asserted that
although federal law may allow state officials to enforce federal law only under limited
circumstances, state officials enforcing state law do “not need to rely on federal law.”243 Judge
Oldham also argued that even if this section of S.B. 4 were conflict preempted to the extent the
232 Id. at 295.
233 Id.
234 Id. at 284, 288.
235 Id. at 285.
236 Id.
237 Id. at 291.
238 Id. at 295.
239 Id. at 317–29 (Oldham, J., dissenting).
240 Id. at 320–21 (Oldham, J., dissenting).
241 Id. at 322 (Oldham, J., dissenting) (internal quotation marks omitted).
242 Id. at 323–24 (Oldham, J., dissenting).
243 Id. at 327 (Oldham, J., dissenting).
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plaintiffs argued, they needed to show that “all applications of [Section 51.02] are preempted”
and that they failed to do so.244
This lawsuit was initially filed under the Biden Administration. With the recent change in
Administration, on February 11, 2025, the Fifth Circuit directed the parties to file supplemental
briefings on whether they had changed positions on any issues on appeal.245 On March 18, 2025,
the Department of Justice filed a notice of voluntary dismissal of its case with the district court.246
On March 21, 2025, the district court ordered a status conference for April 3, 2025.247 Also on
March 21, 2025, the remaining parties submitted their supplemental briefings to the Fifth
Circuit.248 As of the date of this report, a trial on the merits is scheduled with the district court for
July 8, 2025.249
Oklahoma, H.B. 4156 (United States v. Oklahoma)
In April 2024, Oklahoma passed House Bill 4156 (H.B. 4156),250 which was set to go into effect
on July 1, 2024. Similar to Texas’s S.B. 4, H.B. 4156 created new state criminal penalties for
individuals in Oklahoma who entered or reentered the United States unlawfully and subjected
them to mandatory expulsion from Oklahoma.251 Several plaintiffs sued and sought declaratory
and injunctive relief, arguing, among other things, that the law was preempted by federal
immigration law.252 On June 28, 2024, a federal district court judge granted the plaintiffs’ motion
for preliminary injunction and held that H.B. 4156 was field and conflict preempted. The court
relied on analyses in Arizona v. United States as well as the decisions by the Fifth Circuit and
U.S. District Court Judge Ezra in the S.B. 4 litigation. First, the court held that H.B. 4156’s illegal
entry and reentry provisions were field preempted because federal immigration regulation of
entry and reentry is comprehensive enough to infer that Congress did not leave any room for the
states to supplement.253 The court applied the same logic to H.B. 4156’s expulsion provision,
finding sufficient evidence to conclude that Congress meant to occupy the entire field of
expulsion, including for decisions that remove individuals from states.254 The court added that if
244 Id. at 328 (Oldham, J., dissenting).
245 Order, United States v. Texas, No. 24-50149 (5th Cir. Feb. 11, 2025), Dkt. No. 231.
246 Notice of Voluntary Dismissal, United States v. Texas, 719 F. Supp. 3d 640 (W.D. Tex. Mar. 18, 2025) (No. 1:24-
cv-00008-DAE), Dkt. No. 79. Notwithstanding this case, on February 12, 2025, the Justice Department filed a lawsuit
against New York arguing that New York’s Green Light Law (which prohibits the Department of Motor Vehicles from
sharing information with federal immigration officials) violates the Supremacy Clause. See Complaint, United States v.
New York, No. 1:25-CV-0205 (AMN/MJK), 2025 WL 486630, (N.D.N.Y. Feb. 12, 2025), Dkt. No. 1. Among other
things, the Justice Department argues that the Green Light Law is expressly preempted by 8 U.S.C. § 1373, that it is
conflict preempted because it frustrates cooperation and sharing of information between the state and the federal
government and undermines federal immigration enforcement, and that it violates intergovernmental immunity by
attempting to directly regulate the federal government. See id. at 13–16.
247 Order Setting Status Conference, United States v. Texas, 719 F. Supp. 3d 640 (W.D. Tex. Mar. 21, 2025) (No. 1:24cv-00008-DAE), Dkt. No. 80.
248 Letter, United States v. Texas, No. 24-50149 (5th Cir. Mar. 21, 2025), Dkt. No. 250; Plaintiffs-Appellees’
Supplemental Briefing Pursuant to Court Order, No. 24-50149 (5th Cir. Mar. 21, 2025), Dkt. No. 252.
249 Order, United States v. Texas, 719 F. Supp. 3d 640 (W.D. Tex. 2024) (No. 1:24-cv-00008-DAE), Dkt. No. 72.
250 H.B. 4156, 59th Leg., 2d Reg. Sess. (Okla. 2024).
251 United States v. Oklahoma, 739 F. Supp. 3d 985, 994–95 (W.D. Okla. 2024).
252 The federal district court consolidated the cases on June 5, 2024. Order, United States v. Oklahoma, 739 F. Supp. 3d
985 (W.D. Okla. 2024) (No. 5:24-cv-00511-J), Dkt. No. 17.
253 Oklahoma, 739 F. Supp. at 997–99.
254 Id. at 999–1000.
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H.B. 4156 were permitted to stand, any state could create its own immigration policy, and this
would diminish the federal government’s ability to conduct immigration policy with one voice.255
Second, the court held H.B. 4156 was conflict preempted in two ways. H.B. 4156’s provisions on
unlawful entry and reentry and mandatory expulsion were in conflict with federal law because
federal law allows some individuals who initially unlawfully entered the United States to either
receive lawful immigration status or stay in the United States under certain conditions.256 The
court explained that even when an individual receives a removal order from the federal
government, there is at least a chance that that individual could obtain permission from the
federal government to remain in the United States.257 The court next analyzed a more glaring
conflict with H.B. 4156: The law would give state officials authority “to unilaterally arrest,
prosecute, and punish noncitizens for immigration offenses” without direction from the federal
government and in contravention to federal law under 8 U.S.C. § 1357(g).258 This, the court held,
was not Congress’s intention when it created the system of federal and state cooperation in which
state officers could perform federal functions under limited circumstances.259
Finally, the court briefly addressed the defendants’ “invasion at the border” argument and was
unpersuaded that the current situation in Oklahoma presented an exception to the Compact Clause
of the U.S. Constitution that would allow the state to defend itself from an “invasion at the
border.”260
On July 17, 2024, the case was appealed to the Tenth Circuit, and oral arguments were scheduled
for April 10, 2025.261 On March 14, 2025, the federal government, one of the plaintiffs in the
case, filed a notice of voluntary dismissal of their case with the district court.262 On March 16,
2025, the remaining plaintiffs filed a notice regarding the government’s voluntary dismissal and
requested that the district court leave the preliminary injunction in place while next steps are
decided in the case.263 Finally, on March 25, 2025, the Tenth Circuit vacated the oral arguments
scheduled for April 10, 2025, dismissed the appeal as moot, and denied the remaining plaintiffs’
motion to intervene and motion to remand.264
Iowa, S.F. 2340 (United States v. Iowa)
In April 2024, Iowa passed Senate File 2340 (S.F. 2340),265 which was set to go into effect on
July 1, 2024. Similar to Texas’s S.B. 4, Iowa’s S.F. 2340 created two new state criminal penalties
for certain immigration offenses, such as illegal reentry, and gave state judges authority to order
255 Id. at 1002.
256 Id. at 1003–04.
257 Id.
258 Id. at 1004.
259 Id.
260 Id. at 1004–05.
261 Instructions for Cases Set for Oral Argument, United States v. Oklahoma, No. 24-6144 (10th Cir. Feb. 7, 2025),
Dkt. No. 81.
262 Notice of Voluntary Dismissal, United States v. Oklahoma, 739 F. Supp. 3d 985 (W.D. Okla. Mar. 14, 2025)
(No. 5:24-cv-00511-J), Dkt. No. 50.
263 Notice Regarding Voluntary Dismissal Filed by the United States, United States v. Oklahoma, 739 F. Supp. 3d 985
(W.D. Okla. Mar. 16, 2025) (No. 5:24-cv-00511-J), Dkt. No. 51.
264 Order, United States v. Oklahoma, No. 24-6144 (10th Cir. dismissed Mar. 25, 2025), Dkt. No. 91-1.
265 S.B. 2340, 90th Gen. Assembly, Reg. Sess. (Iowa 2024).
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the removal of an alien back to the country from which he or she entered.266 Several plaintiffs
sued and sought declaratory and injunctive relief, arguing, among other things, that the law was
preempted by federal immigration law.267 On June 17, 2024, a federal district court judge granted
the plaintiffs’ motions for preliminary injunction.268 The court held that S.F. 2340 was field and
conflict preempted. Using the Fifth Circuit’s and U.S. District Court Judge Ezra’s analysis as
guidance, the court held that S.F. 2340 was field preempted because the INA established a federal
scheme to regulate immigration and set the terms and conditions by which people could be
admitted to the United States and that the Iowa law interfered with this scheme when it
criminalized behavior that the INA already prohibits.269 According to the court, Iowa could not
implement its own penalties for illegal reentry because Congress did not leave any room for this
kind of state regulation, and doing so would frustrate federal objectives.270
The court further held that S.F. 2340 was conflict preempted. The court reasoned that, under
federal law, some of the plaintiffs would not be criminally liable for federal illegal reentry
because they would be able to use their current immigration status as a legal defense.271 Under the
Iowa law, these same plaintiffs, on the other hand, would not be able to use their current
immigration status as a legal defense and could still be held criminally liable for illegal reentry.
The court stated that this is untenable.272 Finally, the court held that S.F. 2340’s provision giving
state judges authority to order the removal of aliens was also conflict preempted because
Congress had already created a very intricate system by which individuals are removed from the
United States and to what countries, and sometimes, for a variety of reasons, individuals are not
returned to the countries from which they entered.273 According to the court, the Iowa law
prevents the United States from speaking with one voice.274
On January 24, 2025, the Eighth Circuit affirmed the district court, upheld the preliminary
injunction, and held that the three relevant sections of the new Iowa law were conflict
preempted.275 For Section 2, which criminalizes illegal entry and reentry, the court held that Iowa
would be creating its own immigration policy and that this was an obstacle to the broad discretion
federal officials currently have when it comes to enforcing immigration law.276 Specifically,
Section 2, unlike the federal illegal reentry statute, does not contain any exceptions.277 Iowa asked
the court to infer the same exceptions that exist in federal law, but according to the court, Iowa is
266 United States v. Iowa, 737 F. Supp. 3d 725 (S.D. Iowa 2024), vacated, appeal dismissed, No. 24-2265, 2025 WL
1140834, at *1 (8th Cir. Apr. 15, 2025).
267 Id. at 738, 746. The plaintiffs include the federal government, a nonprofit organization, and several individuals. The
federal government filed one motion, and the nonprofit organization and individual plaintiffs filed a separate motion to
enjoin (or prevent) the state law from going into effect. Id. at 738.
268 Id. at 732–33. The district court granted both motions for a preliminary injunction in one opinion. Id.
269 Id. at 747.
270 Id.
271 Id. at 747–48.
272 Id. at 748.
273 Id.
274 Id.
275 United States v. Iowa, 126 F.4th 1334 (8th Cir. 2025), vacated, No. 24-2265, 2025 WL 1140834, at *1 (8th Cir.
Apr. 15, 2025). The same day, the Eighth Circuit issued a separate short order dismissing Iowa’s appeal as to the
nonprofit organization and individual plaintiffs because the court, in its long opinion, upheld the preliminary injunction
of S.F. 2340 and held that that appeal is now moot. See Iowa Migrant Movement for Just. v. Bird, No. 24-2263, 2025
WL 319926, at *1 (8th Cir. Jan. 24, 2025), reh’g granted, vacated, No. 24-2263, 2025 WL 1140762, at *1 (8th Cir.
Apr. 15, 2025).
276 Iowa, 126 F.4th at 1347, 1349.
277 Id. at 1346.
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asking the court “to ignore the plain text of the statute,” and “[t]he plain text of Section 2 has no
exceptions.”278 Further, according to the Eighth Circuit, Section 2 “creates a parallel scheme of
enforcement for immigration law” and complicates United States’ foreign relations.279
For Section 4, which gives state judges authority to order the removal of an alien back to the
country from which he or she entered, the court held that it would also create an obstacle to the
broad discretion immigration officials have over removal decisions.280 Similar to Section 2,
Section 4 also has no exceptions for judges to issue this order, unlike federal law, which allows
federal officials to withhold removal for those who illegally reenter if, for example, an alien
“expresses a fear of returning to the country designated in” his or her reinstated order of
removal.281 The Eighth Circuit held that Section 4 also conflicts with where an alien can be
removed to. Under federal law, if an “alien’s life or freedom would be threatened in” the country
of removal, then that alien can be removed to another country.282 In contrast, Section 4 “mandates
only one destination for an [] alien.”283 The court held that Section 4 conflicts with the principle
that the federal government is entrusted with the removal process.284 Finally, for Section 6, which
prevents a court from delaying prosecution because the federal government is still determining an
individual’s immigration status, the Eighth Circuit held that this section (like the others)
“undermines federal officials’ discretion to decide if, when, and how to address the case of an
individual alien.”285 Iowa argued that a state judge has the option to stop or suspend a prosecution
while the federal determination of an individual’s immigration status is pending, but the court
held that because this discretion would lie with the state courts and not the federal government,
“Iowa could still make its own immigration policy” and therefore this section was also conflict
preempted.286
On March 14, 2025, the federal government, one of the plaintiffs in the case, filed a notice of
voluntary dismissal of the case.287 On March 18, 2025, the remaining plaintiffs filed a motion to
amend their petition for a panel rehearing in light of the federal government’s notice of voluntary
dismissal.288 On March 24, 2025, the defendants filed a petition for a panel rehearing of the
Eighth Circuit’s opinion, and that petition is currently pending before the court.289 On April 15,
2025, the Eight Circuit vacated its prior opinion, vacated the district court’s grant of a preliminary
injunction, dismissed Iowa’s appeal as moot, and remanded “to the district court with instructions
278 Id. at 1346–47.
279 Id. at 1348.
280 Id. at 1351.
281 Id. at 1349 (internal quotation marks omitted) (quoting 8 C.F.R. § 241.8(e)).
282 Id. at 1350.
283 Id.
284 Id.
285 Id. at 1351.
286 Id.
287 Notice of Voluntary Dismissal, United States v. Iowa, 737 F. Supp. 3d 725 (S.D. Iowa Mar. 14, 2025) (No. 4:24-cv-
162-SHL-SBJ), Dkt. No. 46.
288 Motion to Amend Plaintiffs’ Petition for Panel Rehearing, Iowa Migrant Movement for Just. v. Bird, (8th Cir. Mar.
18, 2025) (No. 24-2263) [hereinafter Plaintiffs’ Amended Petition]. The remaining plaintiffs had a pending petition for
rehearing of the Eighth Circuit’s January 24, 2025, order that dismissed their appeal as moot. Petition for Panel
Rehearing and Stay of Mandate, Iowa Migrant Movement for Just. v. Bird, (8th Cir. Feb. 21, 2025) (No. 24-2263). The
circuit court found the plaintiffs’ case moot because the court had affirmed the preliminary injunction in the federal
government’s related case. Now, with the federal government’s voluntary dismissal of the case, the plaintiffs argued
that they have further reasons to show that their appeal is not moot. See Plaintiffs’ Amended Petition at 3.
289 Appellants’ Petition for Panel or En Banc Rehearing, United States v. Iowa, 126 F.4th 1334 (8th Cir. Mar. 14, 2025)
(No. 24-2265).
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to dismiss” the district court case.290 The same day, the Eight Circuit also granted the remaining
plaintiffs’ petition for rehearing and vacated its January 24, 2025, order that dismissed the
remaining plaintiffs’ appeal as moot, thereby reviving their challenge to S.F. 2340.291 This
information is current as of the date of this report.
Other Recent State Measures Addressing Unlawfully Present
Aliens
In addition to the state enactments and associated legal challenges discussed above, other states
have adopted similar measures to deter the presence of unlawfully present aliens within their
jurisdictions.
On June 18, 2024, Louisiana Governor Jeff Landry signed Senate Bill 388, which was modeled
after Texas’s S.B. 4.292 The main provisions of the Louisiana statute do not go into effect unless or
until either the Supreme Court issues a final decision upholding S.B. 4 or a constitutional
amendment is ratified that authorizes states to restrict unlawfully present aliens from entering
their jurisdictions.
In November 2024, Arizona voters agreed to Proposition 314, or the “Secure the Border Act.”293
The proposition contained components that resembled Texas’s S.B. 4. Among other things,
Proposition 314 makes it a state crime to enter Arizona from any foreign nation (e.g., Mexico)
other than through an official port of entry294 and authorizes state court judges to order the return
of an alien back to the country from which he or she entered.295 These two components cannot be
enforced until Texas’s S.B. 4, or any other similar state law, is in effect for 60 days.296 On April 2,
2025, a lawsuit was filed in Arizona state court challenging the proposition.297
On February 13, 2025, Florida Governor Ron DeSantis signed into law Senate Bill 4C (S.B. 4C),
which is similarly modeled after Texas’s S.B. 4 and went into effect immediately.298 On April 2,
2025, a group of plaintiffs sued, claiming that S.B. 4C is unconstitutional and conflicts with the
Supremacy Clause, among other things.299 On April 4, 2025, a federal district judge granted a
temporary restraining order, blocking enforcement of S.B. 4C.300
290 United States v. Iowa, No. 24-2265, 2025 WL 1140834, at *1 (8th Cir. Apr. 15, 2025).
291 Iowa Migrant Movement for Just. v. Bird, No. 24-2263, 2025 WL 1140762, at *1 (8th Cir. Apr. 15, 2025).
292 See LA. STAT. ANN. §§ 14:112.11–13 (2024).
293 Steve Nielsen & Gabriel Sandoval, Arizona Voters Approve State-Level Immigration Enforcement, FOX10 PHOENIX
(Nov. 6, 2024, 5:43 PM), https://www.fox10phoenix.com/election/arizona-voters-approve-state-level-immigrationenforcement.
294 ARIZ. REV. STAT. ANN. § 13-4295.01.
295 Id. § 13-4295.03.
296 Id. § 13-4295.04.
297 See Verified Complaint for Declaratory Judgment and Injunction, Living United for Change in Ariz. v. Arizona, No.
CV2025-011729 (Ariz. Sup. Apr. 2, 2025) (No. CV2025-011729).
298 See FLA. STAT. §§ 811.
299 See Class Action Complaint for Injunctive and Declaratory Relief, Florida Immigr. Coalition v. Uthmeier,
No. 1:25CV21524, 2025 WL 1006475, at *1 (S.D. Fla. Apr. 2, 2025).
300 See Order, Florida Immigr. Coalition v. Uthmeier, No. 1:25-cv-21524-KMW (S.D. Fla. Apr. 4, 2025), Dkt. No. 28.
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Considerations for Congress
Recent state measures seeking to deter unlawfully present aliens from entering or remaining in
their jurisdictions have prompted new legal challenges. The Supreme Court’s decision in Arizona
looms large over these suits. Whereas plaintiffs look to the majority opinion in Arizona to argue
that these state laws impermissibly conflict with the federal immigration framework, the states
contend that they retain sovereign authority to take action to prevent an “invasion” of their
borders. The Supreme Court and Congress have yet to address this issue separately or
collectively.301 From the pending litigation thus far, no federal court has determined that there is
currently an “invasion at the border.” According to Judge Ezra from the Western District of Texas,
for example, the definition of “invasion”302 has been interpreted over time to refer to “a hostile
and organized military force,” and the Compact Clause “was to be used sparingly for temporary,
exigent, and dangerous circumstances.”303 Judge Ezra rejected304 Texas’s “invasion at the border”
argument for three reasons: A surge in people illegally crossing the border does not constitute an
invasion, Texas is not at war if it enforces S.B. 4, and if Texas were at war then “it would have to
abide by federal directives in waging that war.”305 On the other hand, Judge Ho from the Fifth
Circuit, in a concurring and dissenting opinion in United States v. Abbott, argued that Texas has
the right to respond to an “invasion” under the Compact Clause of the Constitution and that
Texas’s invocation of that right is a nonjusticiable political question.306
The “invasion at the border” claim has also emerged in spaces outside of litigation.307 In
November 2022, before Texas passed S.B. 4, Texas Governor Abbott sent then-President Biden a
letter detailing how, according to the governor, the Biden Administration had failed to protect the
state from an “invasion at the border”—in violation of the Constitution—and that as a result
Texas would have to take matters into its own hands.308 In January 2024, a group of former
Federal Bureau of Investigation officials wrote a letter to Congress and warned that there is an
301 Although the courts have yet to address this issue on point, in the 1990s, several courts suggested—albeit relying on
other parts of the Constitution and not the Compact Clause—that an invasion means a military invasion or an armed
hostility. C.f., e.g., New Jersey v. United States, 91 F.3d 463, 468 (3d Cir. 1996) (suggesting an invasion under the
Invasion Clause of the Constitution refers to a military invasion); Padavan v. United States, 82 F.3d 23, 28 (2d Cir.
1996) (suggesting that an invasion under the Invasion Clause requires an armed hostility).
302 United States v. Texas, 719 F. Supp. 3d 640, 682 (W.D. Tex. 2024) (“The natural and normal meaning of ‘invade,’
as shown by the predominant dictionary definition, is to enter a country with hostile intent, typically to assault, attack,
seize, or plunder.”); see id. at 683 (“The natural and plain meaning of ‘invasion’ within the [Compact Clause] is a
narrow and time-constrained response in the face of imminent military emergency.”).
303 Id. at 680.
304 The district court in Oklahoma v. United States also rejected the “invasion at the border” argument for the same
reasons. See 739 F. Supp. 3d 985, 1004–05 (W.D. Okla. June 28, 2024).
305 Texas, 719 F. Supp. 3d at 679.
306 United States v. Abbott, 110 F.4th 700, 725 (5th Cir. 2024) (Ho, J., concurring in part and dissenting in part).
307 Republican Governors Band Together, Issue Joint Statement Supporting Texas’ Constitutional Right to SelfDefense, REPUBLICAN GOVERNORS ASSOCIATION (Jan. 25, 2024), https://www.rga.org/republican-governors-bantogether-issue-joint-statement-supporting-texas-constitutional-right-self-defense/.
308 Letter from Greg Abbott, Governor of Texas, to Joseph R. Biden, President of the United States (Nov. 16, 2022),
https://gov.texas.gov/uploads/files/press/BidenJoseph_11.16.22.pdf. Also in 2022, Senator Marshall declared that the
situation at the southern border was an invasion according to the Constitution and requested “unanimous consent to
pass his new resolution” declaring it as such. See Press Release, Roger Marshall, Senator, U.S. Senate, Sen. Marshall:
Joe Biden’s Open Borders Agenda Exposed States to Invasion (Aug. 4, 2022),
https://www.marshall.senate.gov/newsroom/press-releases/sen-marshall-joe-bidens-open-borders-agenda-exposedstates-to-invasion/.
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“invasion” of people coming from hostile nations.309 On January 20, 2025, President Trump
issued Executive Order 10888, “Guaranteeing the States Protection Against Invasion,” in which
he declared that “the current situation at the southern border qualifies as an invasion under [the
Guarantee Clause] of the Constitution.”310
Another issue Congress may want to consider is the possibility that the pending challenges to
state measures addressing the unlawfully present population may end up before the Supreme
Court. If this occurs, the Supreme Court may consider the preemptive effect of federal
immigration law, the continuing vitality of the Court’s decision in Arizona, and whether states’
invocation of sovereign authority to respond to an “invasion” alters the Court’s legal analysis.
Congress has options if it seeks to address the issues present in the pending preemption cases as
well. For example, H. Res. 1031, introduced in the 118th Congress, would have expressed that the
situation at the southern U.S. border is an invasion “to help support legal arguments of states in
federal court.”311 As another example, H. Res. 50, introduced in the 119th Congress, would
declare, among other things, that “from 2021 through 2024, the United States failed to protect the
[southern border states] against invasion pursuant to [the Guarantee Clause of the Constitution]”
and that states have “the sovereign right to exclude from [their] territory any person who does not
have the right to be here” and can defend themselves from invasion.312
Congress may also choose to enact legislation that repeals existing federal immigration statutes
upon which some states have patterned their own enforcement measures. For example, the New
Way Forward Act (H.R. 2374) in the 118th Congress would have, among other things, repealed
the illegal entry and reentry statutes under 8 U.S.C. §§ 1325 and 1326 and the statutes on
communication and coordination between federal and state or local law enforcement under 8
U.S.C. §§ 1373 and 1644.313 Alternatively, Congress may enact legislation that provides the states
with greater control over immigration regulation within their borders. For example, the State and
Immigration Enforcement Act (H.R. 218) in the 119th Congress would allow states and localities
to enact and enforce civil and “criminal penalties that penalize the same conduct that is
prohibited” in the civil and criminal provisions of immigration laws.314
309 Senator Ron Johnson (@SenRonJohnson), X (Jan. 25, 2024, 2:41 PM)
https://x.com/SenRonJohnson/status/1750604869910602022?s=20.
310 See Exec. Order No. 10,888, 90 Fed. Reg. 8,333 (Jan. 20, 2025). President Trump issued other executive orders that
also classified the situation at the border as an “invasion.” See, e.g., Exec. Order No. 10,886, 90 Fed. Reg. 8,327 (Jan.
20, 2025); Exec. Order No. 14,165, 90 Fed. Reg. 8,467 (Jan. 20, 2025); Exec. Order No. 14,159, 90 Fed. Reg. 8,443
(Jan. 20, 2025).
311 See H. Res. 1031, 118th Cong. (2023); Press Release, Daniel Webster, Representative, U.S. House of
Representatives, Webster Introduces Bill Recognizing Border Crisis as an Invasion (Mar. 1, 2024),
https://webster.house.gov/2024/3/webster-introduces-bill-recognizing-border-crisis-as-an-invasion. In February 2024,
Senators Marshall and Tuberville went to the Senate floor and demanded passage of Senator Marshall’s 2022 resolution
that would declare the situation at the southern border an invasion. See Press Release, Roger Marshall, Senator, U.S.
Senate, Senator Marshall Leads Efforts to Declare an Invasion at the Southern Border on Senate Floor (Feb. 7, 2024),
https://www.marshall.senate.gov/newsroom/press-releases/senator-marshall-leads-efforts-to-declare-an-invasion-at-thesouthern-border-on-senate-floor/. Doing so would “reaffirm states’ Constitutional right to protect themselves from an
invasion, which would immediately empower Governors to secure the southern border without interference from the
federal government.” Id.
312 See H. Res. 50, 119th Cong. (2025).
313 See New Way Forward Act, H.R. 2374, 118th Cong. (2023).
314 See State Immigration Enforcement Act, H.R. 218, 119th Cong. (2025).
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Congress may also enact legislation that further expands immigration enforcement cooperation
between the federal government and state and local governments. For example, the 287(g)
Program Protection Act (H.R. 756) in the 119th Congress would require the Department of
Homeland Security to approve 287(g) applications within 90 days and would prevent termination
or denial of any applications without a compelling reason.315 On the other hand, Congress may
constrict this kind of cooperation. For example, the PROTECT Immigration Act (S. 1336) in the
117th Congress would have rescinded state and local immigration enforcement authority under 8
U.S.C. § 1357(g).316
Author Information
Alejandra Aramayo
Legislative Attorney
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan
shared staff to congressional committees and Members of Congress. It operates solely at the behest of and
under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other
than public understanding of information that has been provided by CRS to Members of Congress in
connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not
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copy or otherwise use copyrighted material.
315 See 287(g) Program Protection Act, H.R. 756, 119th Cong. (2025). Section 1357(g) of Title 8 of the U.S. Code, or
more commonly known as the “287(g) program,” authorizes U.S. Immigration and Customs Enforcement (ICE) to
work with state and local law enforcement to perform certain immigration functions under ICE’s direction and
oversight. See 8 U.S.C. § 1357(g); see also Delegation of Immigration Authority Section 287(g) Immigration and
Nationality Act, U.S. ICE, https://www.ice.gov/identify-and-arrest/287g (last visited Apr. 30, 2025).
316 See PROTECT Immigration Act, S. 1336, 117th Cong. (2021).
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This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.