1 (Slip Opinion) OCTOBER TERM, 2011

Syllabus

NOTE: Where it is feasible, a syllabus (headnote) will be released, as is being done in connection with this case, at the time the opinion is issued. The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience of the reader. See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.


## SUPREME COURT OF THE UNITED STATES

Syllabus

ARIZONA ET AL

. v . UNITED STATES

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR

THE NINTH CIRCUIT

No. 11–182. Argued April 25, 2012—Decided June 25, 2012

An Arizona statute known as S. B. 1070 was enacted in 2010 to address

pressing issues related to the large number of unlawful aliens in the State. The United States sought to enjoin the law as preempted. The District Court issued a preliminary injunction preventing four of its provisions from taking effect. Sect ion 3 makes failure to comply with federal alien-registration requirem ents a state misdemeanor; §5(C) makes it a misdemeanor for an unauthorized alien to seek or engage in work in the State; §6 authorizes state and local officers to arrest without a warrant a person “the offi cer has probable cause to believe . . . has committed any public offense that makes the person remova

ble from the United States”; and §2 (B) requires officers conducting a stop, detention, or arrest to make efforts, in some circumstances, to verify the person’s immigration status with the Federal Government. The Ninth Circuit affirmed, agreeing that the United States had es

tablished a likelihood of success on its preemption claims.

Held : 1. The Federal Government’s broad, undoubted power over immi

gration and alien status rests, in part, on its constitutional power to “establish an uniform Rule of Naturalization,” Art. I, §8, cl. 4, and on its inherent sovereign power to control and conduct foreign relations,

see Toll v. Moreno , 458 U. S. 1, 10. Federal governance is extensive and complex. Among other things, federal law specifies categories of aliens who are ineligible to be admitted to the United States, 8

U. S. C. §1182; requires aliens to register with the Federal Govern

ment and to carry proof of status, §§1304(e), 1306(a); imposes sanc

tions on employers who hire unauthorized workers, §1324a; and spec

ifies which aliens may be removed and the procedures for doing so, see §1227. Removal is a civil matter , and one of its principal features2 ARIZONA v. UNITED STATES

Syllabus

is the broad discretion exercised by immigration officials, who must decide whether to pursue removal at all. Immigration and Customs Enforcement (ICE), an agency within the Department of Homeland Security, is responsible for identi fying, apprehending, and removing illegal aliens. It also operates the Law Enforcement Support Center, which provides immigration status in formation to federal, state, and local officials around the clock. Pp. 2–7.

2. The Supremacy Clause give s Congress the power to preempt state law. A statute may contain an express preemption provision,

see, e.g., Chamber of Commerce of United States of America v. Whit

ing , 563 U. S. ___, ___, but state law must also give way to federal law in at least two other circumstances. First, States are precluded from regulating conduct in a fi eld that Congress has determined must be regulated by its exclusive governance. See Gade v. National Solid Wastes Management Assn., 505 U. S. 88, 115. Intent can be in

ferred from a framework of regulati on “so pervasive . . . that Con

gress left no room for the States to supplement it” or where a “federal interest is so dominant that the federal system will be assumed to preclude enforcement of state laws on the same subject.” Rice v. San

ta Fe Elevator Corp. , 331 U. S. 218, 230. Second, state laws are preempted when they conflict with federal law, including when they
stand “as an obstacle to the acco mplishment and execution of the full purposes and objectives of Congress.” Hines v. Davidowitz , 312 U. S. 52, 67. Pp. 7–8.

3. Sections 3, 5(C), and 6 of S. B. 1070 are preempted by federal law. Pp. 8–19. (a) Section 3 intrudes on the field of alien registration, a field in which Congress has left no room for States to regulate. In Hines, a state alien-registration program was struck down on the ground that Congress intended its “complete” fe deral registration plan to be a “single integrated and all-embracing system.” 312 U. S., at 74. That scheme did not allow the States to “curtail or complement” federal
law or “enforce additional or auxiliary regulations.” Id. , at 66–67. The federal registration framework remains comprehensive. Because Congress has occupied the field, ev en complementary state regulation is impermissible. Pp. 8–11. (b) Section 5(C)’s criminal penalty stands as an obstacle to the federal regulatory system. The Immigration Reform and Control Act of 1986 (IRCA), a comprehensive framework for “combating the em

ployment of illegal aliens,” Hoffman Plastic Compounds, Inc. v. NLRB , 535 U. S. 137, 147, makes it illegal for employers to knowing

ly hire, recruit, refer, or continue to employ unauthorized workers, 8

U. S. C. §§1324a(a)(1)(A), (a)(2), and requires employers to verify pro

spective employees’ employme nt authorization status,3 Cite as: 567 U. S. ____ (2012)

Syllabus

§§1324a(a)(1)(B), (b). It imposes criminal and civil penalties on em

ployers, §§1324a(e)(4), (f), but only civil penalties on aliens who seek, or engage in, unauthorized employment, e.g., §§1255(c)(2), (c)(8). IRCA’s express preemption provision, though silent about whether additional penalties may be imposed against employees, “does not bar the ordinary working of conflict pr e-emption principles” or impose a “special burden” making it more difficult to establish the preemption of laws falling outside the clause. Geier v. American Honda Motor
Co. , 529 U. S. 861, 869–872. The correct instruction to draw from the text, structure, and history of IRCA is that Congress decided it would be inappropriate to impose criminal penalties on unauthorized em

ployees. It follows that a state law to the contrary is an obstacle to the regulatory system Congress chose. Pp. 12–15. (c) By authorizing state and lo cal officers to make warrantless arrests of certain aliens suspected of being removable, §6 too creates an obstacle to federal law. As a general rule, it is not a crime for a
removable alien to remain in the United States. The federal scheme instructs when it is appropriate to arrest an alien during the removal process. The Attorney General in some circumstances will issue a warrant for trained federal immigration officers to execute. If no fed

eral warrant has been issued, thes e officers have more limited au

thority. They may arrest an alien for being “in the United States in violation of any [immigration] law or regulation,” for example, but on

ly where the alien “is likely to es cape before a warrant can be ob

tained.” §1357(a)(2). Section 6 atte mpts to provide state officers with even greater arrest authority, which they could exercise with no in

struction from the Federal Government. This is not the system Con

gress created. Federal law specifie s limited circumstances in which state officers may perform an immigration officer’s functions. This
includes instances where the Attorn ey General has granted that au

thority in a formal agreement with a state or local government. See,

e.g., §1357(g)(1). Although federal law permits state officers to “coop

erate with the Attorney General in the identification, apprehension, detention, or removal of aliens no t lawfully present in the United States,” §1357(g)(10)(B), this does not encompass the unilateral deci

sion to detain authorized by §6. Pp. 15–19.

4. It was improper to enjoin §2 (B) before the state courts had an opportunity to construe it and with out some showing that §2(B)’s en

forcement in fact conflicts with fe deral immigration law and its objec

tives. Pp. 19–24. (a) The state provision has th ree limitations: A detainee is pre

sumed not to be an illegal alien if he or she provides a valid Arizona
driver’s license or similar identifi cation; officers may not consider race, color, or national origin “except to the extent permitted by the4 ARIZONA v. UNITED STATES

Syllabus

United States [and] Arizona Consti tution[s]”; and §2(B) must be “im

plemented in a manner consistent with federal law regulating immi

gration, protecting the civil rights of all persons and respecting the privileges and immunities of United States citizens.” P. 20. (b) This Court finds unpersuasiv e the argument that, even with those limits, §2(B) must be held preempted at this stage. Pp. 20–24. (1) The mandatory nature of the status checks does not inter

fere with the federal immigration scheme. Consultation between fed

eral and state officials is an important feature of the immigration system. In fact, Congress has encouraged the sharing of information about possible immigration violations. See §§1357(g)(10)(A), 1373(c).
The federal scheme thus leaves room for a policy requiring state offi

cials to contact ICE as a routine matter. Cf. Whiting , 563 U. S., at ___. Pp. 20–21. (2) It is not clear at this stage and on this record that §2(B), in practice, will require state officers to delay the release of detainees for no reason other than to verify their immigration status. This would raise constitutional concerns. And it would disrupt the federal framework to put state officers in the position of holding aliens in custody for possible unlawful presence without federal direction and supervision. But §2(B) could be read to avoid these concerns. If the law only requires state officers to conduct a status check during the course of an authorized, lawful detention or after a detainee has been released, the provision would likely survive preemption—at least ab

sent some showing that it has othe r consequences that are adverse to federal law and its objectives. With out the benefit of a definitive in

terpretation from the state courts, it would be inappropriate to as

sume §2(B) will be construed in a way that conflicts with federal law.
Cf. Fox v. Washington , 236 U. S. 273, 277. This opinion does not foreclose other preemption and consti tutional challenges to the law as interpreted and applied after it goes into effect. Pp. 22–24.

641 F. 3d 339, affirmed in part, reversed in part, and remanded.

K ENNEDY

, J., delivered the opinion of the Court, in which R OBERTS

, C. J., and G INSBURG , B REYER

, and S OTOMAYOR

, JJ., joined. S CALIA

, J.,

T HOMAS

, J., and A LITO

, J., filed opinions concurring in part and dissent

ing in part. K AGAN

, J., took no part in the co nsideration or decision of

the case._________________

_________________ 1 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

NOTICE: This opinion is subject to formal revision before publication in the preliminary print of the United States Reports. Readers are requested tonotify the Reporter of Decisions, Supreme Court of the United States, Washington, D. C. 20543, of any typographical or other formal errors, in order that corrections may be made before the preliminary print goes to press.


## SUPREME COURT OF THE UNITED STATES

No. 11–182

ARIZONA, ET AL ., PETITIONERS v. UNITED STATES

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF

APPEALS FOR THE NINTH CIRCUIT

[June 25, 2012]

J USTICE K ENNEDY delivered the opinion of the Court.
To address pressing issues related to the large number of aliens within its borders who do not have a lawful right to be in this country, the State of Arizona in 2010 enacted a statute called the Support Our Law Enforcement and Safe Neighborhoods Act. The law is often referred to as
S. B. 1070, the version introduced in the state senate. Seealso H. 2162 (2010) (amending S. 1070). Its stated purpose is to “discourage and deter the unlawful entry andpresence of aliens and economic activity by persons unlawfully present in the United St ates.” Note following Ariz.Rev. Stat. Ann. §11–1051 (West 2012). The law’s provisions establish an official state policy of “attrition through
enforcement.” Ibid. The question before the Court is whether federal law preempts and renders invalid four separate provisions of the state law.

I
The United States filed this suit against Arizona, seeking to enjoin S. B. 1070 as preempted. Four provisions of
the law are at issue here. Two create new state offenses.Section 3 makes failure to comply with federal alienregistration requirements a state misdemeanor. Ariz.2 ARIZONA v. UNITED STATES

Opinion of the Court

Rev. Stat. Ann. §13–1509 (West Supp. 2011). Section 5, inrelevant part, makes it a misdemeanor for an unauthorized alien to seek or engage in work in the State; this provision is referred to as §5(C). See §13–2928(C). Two other provisions give specific arrest authority and investigative duties with respect to certain aliens to state and
local law enforcement officers. Section 6 authorizes officers to arrest without a warr ant a person “the officer has probable cause to believe . . . has committed any public offense that makes the person removable from the UnitedStates.” §13–3883(A)(5). Section 2(B) provides that officers who conduct a stop, detention, or arrest must in some
circumstances make efforts to verify the person’s immigration status with the Federal Government. See §11– 1051(B) (West 2012).
The United States District Court for the District of Arizona issued a preliminary injunction preventing the four provisions at issue from taking effect. 703 F. Supp. 2d 980, 1008 (2010). The Court of Appeals for the Ninth Circuit affirmed. 641 F. 3d 339, 366 (2011). It agreed that
the United States had established a likelihood of successon its preemption claims. The Court of Appeals was unanimous in its conclusion that §§3 and 5(C) were likely preempted. Judge Bea dissented from the decision to uphold the preliminary injunction against §§2(B) and 6.This Court granted certiorari to resolve important questions concerning the interaction of state and federal power with respect to the law of immigration and alien status. 565 U. S. ___ (2011).

II
A

The Government of the United States has broad, undoubted power over the subject of immigration and the
status of aliens. See Toll v. Moreno , 458 U. S. 1, 10 (1982); see generally S. Legomsky & C. Rodríguez, Immigration3 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

and Refugee Law and Policy 115–132 (5th ed. 2009). This authority rests, in part, on the National Government’s constitutional power to “estab lish an uniform Rule of Naturalization,” U. S. Const., Art. I, §8, cl. 4, and its inherent power as sovereign to co ntrol and conduct relations with foreign nations, see Toll

, supra, at 10 (citing United
States v. Curtiss-Wright Export Corp. , 299 U. S. 304, 318 (1936)). The federal power to determine immigration policy is well settled. Immigration polic y can affect trade, investment, tourism, and diplomatic relations for the entire Nation, as well as the perceptions and expectations of aliens in this country who seek the full protection of its laws. See, e.g., Brief for Argentina et al. as Amici Curiae;

see also Harisiades v. Shaughnessy , 342 U. S. 580, 588–589 (1952). Perceived mistreatment of aliens in the United States may lead to harmful reciprocal treatment
of American citizens abroad. See Brief for Madeleine K. Albright et al. as Amici Curiae 24–30. It is fundamental that foreign countries concerned about the status, safety, and security of their nationals in the
United States must be able to confer and communicate onthis subject with one national sovereign, not the 50 separate States. See Chy Lung v. Freeman , 92 U. S. 275, 279– 280 (1876); see also The Federalist No. 3, p. 39 (C. Rossiter ed. 2003) (J. Jay) (observing that federal power would be necessary in part because “bordering States . . . under theimpulse of sudden irritation, and a quick sense of apparent interest or injury” might take action that would undermine foreign relations). This Court has reaffirmed that“[o]ne of the most important and delicate of all international relationships . . . has to do with the protection of thejust rights of a country’s own nationals when those nationals are in another country.” Hines v. Davidowitz , 312
U. S. 52, 64 (1941). Federal governance of immigration and alien status is4 ARIZONA v. UNITED STATES

Opinion of the Court

extensive and complex. Congress has specified categories of aliens who may not be admitted to the United States. See 8 U. S. C. §1182. Unlawful entry and unlawful reentry into the country are federal offenses. §§1325, 1326. Once here, aliens are required to register with the Federal Government and to carry proof of status on their person. See §§1301–1306. Failure to do so is a federalmisdemeanor. §§1304(e), 1306(a). Federal law also authorizes States to deny noncitizens a range of public benefits, §1622; and it imposes sanctions on employers who hire unauthorized workers, §1324a. Congress has specified which aliens may be removed from the United States and the procedures for doing so. Aliens may be removed if they were inadmissible at the time of entry, have been convicted of certain crimes, or meet other criteria set by fe deral law. See §1227. Removal is a civil, not criminal, matter. A principal feature of the removal system is the broad discretion exercised byimmigration officials. See Brief for Former Commissioners of the United States I mmigration and Naturalization
Service as Amici Curiae 8–13 (hereinafter Brief for Former INS Commissioners). Federal officials, as an initial matter, must decide whether it makes sense to pursue removal at all. If removal proceedings commence, aliens may seek asylum and other discretionary relief allowing them to remain in the country or at least to leave without formal removal. See §1229a(c)(4); see also, e.g., §§1158(asylum), 1229b (cancellation of removal), 1229c (voluntary departure).Discretion in the enforcement of immigration law embraces immediate human concerns. Unauthorized workers trying to support their families, for example, likelypose less danger than alien smugglers or aliens who commit a serious crime. The equities of an individual case may turn on many factors, including whether the alien has children born in the United States, long ties to the5 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

community, or a record of dist inguished military service. Some discretionary decisions involve policy choices that bear on this Nation’s international relations. Returning an alien to his own country may be deemed inappropriate
even where he has committed a removable offense or fails to meet the criteria for admission. The foreign state may be mired in civil war, complicit in political persecution, or enduring conditions that create a real risk that the alien or his family will be harmed upon return. The dynamicnature of relations with other countries requires the Executive Branch to ensure that enforcement policies are consistent with this Nation’s fo reign policy with respect to

these and other realities. Agencies in the Department of Homeland Security play a major role in enforcing the country’s immigration laws.United States Customs and Border Protection (CBP) is responsible for determining the admissibility of aliens and securing the country’s borders. See Dept. of Homeland Security, Office of Immigrat ion Statistics, Immigration Enforcement Actions: 2010, p. 1 (2011). In 2010, CBP’s Border Patrol apprehended almost half a million people.

Id. , at 3. Immigration and Customs Enforcement (ICE), a second agency, “conducts crimi nal investigations involving the enforcement of immigration-related statutes.” Id. , at

2. ICE also operates the Law Enforcement Support Center. LESC, as the Center is known, provides immigration status information to federal, state, and local officialsaround the clock. See App. 91. ICE officers are responsible “for the identification, apprehension, and removal ofillegal aliens from the United States.” Immigration Enforcement Actions, supra, at 2. Hundreds of thousands of aliens are removed by the Federal Government every year.
See id., at 4 (reporting there were 387,242 removals, and 476,405 returns without a removal order, in 2010).6 ARIZONA v. UNITED STATES

Opinion of the Court

B
The pervasiveness of federal regulation does not diminish the importance of immigration policy to the States.Arizona bears many of the consequences of unlawful immigration. Hundreds of thousands of deportable aliens are apprehended in Arizona each year. Dept. of Homeland Security, Office of Immigration Statistics, 2010 Yearbookof Immigration Statistics 93 (2011) (Table 35). Unauthorized aliens who remain in the State comprise, by one estimate, almost six percent of the population. See Passel& Cohn, Pew Hispanic Center, U. S. Unauthorized Immigration Flows Are Down Sharply Since Mid-Decade 3 (2010). And in the State’s most populous county, these aliens are reported to be resp onsible for a disproportionate share of serious crime. See, e.g., Camarota & Vaughan, Center for Immigration Studies, Immigration and Crime:Assessing a Conflicted Situation 16 (2009) (Table 3) (estimating that unauthorized aliens comprise 8.9% of the population and are responsible for 21.8% of the felonies in Maricopa County, which includes Phoenix).Statistics alone do not capture the full extent of Arizona’s concerns. Accounts in the record suggest there is an “epidemic of crime, safety risk s, serious property damage, and environmental problems” associated with the influx of illegal migration across priv ate land near the Mexican border. Brief for Petitioners 6. Phoenix is a major city of the United States, yet signs along an interstate highway 30 miles to the south warn the public to stay away. One reads, “DANGER—PUBLIC WARNING—TRAVEL NOT RECOMMENDED / Active Drug and Human Smuggling Area / Visitors May Encounter Armed Criminals and Smuggling Vehicles Traveling at High Rates of Speed.” App. 170; see also Brief for Petitioners 5–6. The problems posed to the State by illegal immigration must not be

underestimated. These concerns are the background for the formal legal7 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

analysis that follows. The issue is whether, under preemption principles, federal law permits Arizona to implement the state-law provisions in dispute.

III

Federalism, central to the co nstitutional design, adoptsthe principle that both the National and State Governments have elements of sovereignty the other is bound to respect. See Gregory v. Ashcroft , 501 U. S. 452, 457 (1991); U. S. Term Limits, Inc. v. Thornton , 514 U. S. 779, 838 (1995) (K ENNEDY

, J., concurring). From the existence of two sovereigns follows the possibility that laws can be in conflict or at cross-purposes. The Supremacy Clauseprovides a clear rule that federal law “shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.” Art. VI, cl. 2. Under this principle, Congress has the power to preempt state law. See Crosby v. National For

eign Trade Council , 530 U. S. 363, 372 (2000); Gibbons

v. Ogden , 9 Wheat. 1, 210–211 (1824). There is no doubt that Congress may withdraw specified powers from the States by enacting a statute containing an express preemption provision. See, e.g., Chamber of Commerce of United States of America v. Whiting , 563 U. S. ___, ___ (2011) (slip op., at 4). State law must also give way to federal law in at least two other circumstances. First, the States are precluded from regulating conduct in a field that Congress, actingwithin its proper authority, has determined must be regulated by its exclusive governance. See Gade v. National Solid Wastes Management Assn., 505 U. S. 88, 115 (1992). The intent to displace state law altogether 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 intere st . . . so dominant that the8 ARIZONA v. UNITED STATES

Opinion of the Court

federal system will be assumed to preclude enforcement of state laws on the same subject.” Rice v. Santa Fe Elevator Corp. , 331 U. S. 218, 230 (1947); see English v. General
Elec. Co. , 496 U. S. 72, 79 (1990). Second, state laws are preempted when they conflict
with federal law. Crosby, supra, at 372. This includes cases where “compliance with both federal and state regulations is a physical impossibility,” Florida Lime & Avocado Growers, Inc. v. Paul , 373 U. S. 132, 142–143 (1963), and those instances where the challenged state law“stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress,”

Hines , 312 U. S., at 67; see also Crosby

, supra , at 373 (“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”). In preemption analysis, courts should assume that “the historic police powers of the States” are not superseded“unless that was the clear and manifest purpose of Congress.” Rice

, supra, at 230; see Wyeth v. Levine , 555 U. S. 555, 565 (2009). The four challenged provisions of the state law each must be examined under these preemption principles.

IV
A
Section 3

Section 3 of S. B. 1070 creates a new state misdemeanor. It forbids the “willful failure to complete or carry an alien registration document . . . in violation of 8 United States Code section 1304(e) or 1306(a).” Ariz. Rev. Stat. Ann. §11–1509(A) (West Supp. 2011). In effect, §3 adds a state-law penalty for conduct proscribed by federal law.
The United States contends that this state enforcement mechanism intrudes on the field of alien registration, a field in which Congress has left no room for States toCite as: 567 U. S. ____ (2012) 9

Opinion of the Court

regulate. See Brief for United States 27, 31.
The Court discussed federal alien-registration requirements in Hines v. Davidowitz , 312 U. S. 52. In 1940, as international conflict spread, Congress added to federalimmigration law a “complete system for alien registration.” Id. , at 70. The new federal law struck a careful balance. It punished an alien’s willful failure to register but did not require aliens to carry identification cards.There were also limits on the sharing of registration records and fingerprints. The Court found that Congress intended the federal plan for registration to be a “single integrated and all-embracing system.” Id. , at 74. Because this “complete scheme . . . fo r the registration of aliens” touched on foreign relations, it did not allow the States to “curtail or complement” federal law or to “enforce additional or auxiliary regulations.” Id. , at 66–67. As a consequence, the Court ruled that Pennsylvania could not enforce its own alien-registration program. See id. , at 59, 74.The present regime of federal regulation is not identical to the statutory fr amework considered in Hines , but it remains comprehensive. Federal law now includes a requirement that aliens carry proof of registration. 8

U. S. C. §1304(e). Other aspects, however, have stayed the same. Aliens who remain in the country for more than 30 days must apply for registrati on and be fingerprinted. Compare §1302(a) with id. , §452(a) (1940 ed.). Detailed information is required, and any change of address has to be reported to the Fede ral Government. Compare §§1304(a), 1305(a) (2006 ed.), with id. , §§455(a), 456 (1940 ed.). The statute continues to provide penalties for the willful failure to register. Compare §1306(a) (2006 ed.),

with id. , §457 (1940 ed.).The framework enacted by Congress leads to the conclusion here, as it did in Hines

, that the Federal Government has occupied the field of alien registration. See American

Ins. Assn. v. Garamendi , 539 U. S. 396, 419, n. 11 (2003)10 ARIZONA v. UNITED STATES

Opinion of the Court

(characterizing Hines as a field preemption case); Pennsyl

vania v. Nelson , 350 U. S. 497, 504 (1956) (same); see also Dinh, Reassessing the Law of Preemption, 88 Geo. L. J.2085, 2098–2099, 2107 (2000) (same). The federal statutory directives provide a full set of standards governingalien registration, including the punishment for noncompliance. It was designed as a “ ‘harmonious whole.’ ”

Hines

, supra, at 72. Where Congress occupies an entirefield, as it has in the field of alien registration, even complementary state regulation is impermissible. Field preemption reflects a congressional decision to foreclose anystate regulation in the area, even if it is parallel to federal standards. See Silkwood v. Kerr-McGee Corp. , 464
U. S. 238, 249 (1984). Federal law makes a single sovereign responsible for maintaining a comprehensive and unified system to keep track of aliens within the Nation’s borders. If §3 of the Arizona statute were valid, ev ery State could give itself independent authority to pros ecute federal registration violations, “diminish[ing] the [Federal Government]’s control over enforcement” and “detract[ing] from the ‘integrated scheme of regulation’ created by Congress.” Wisconsin Dept. of Industry v. Gould Inc. , 475 U. S. 282, 288–289 (1986). Even if a State may make violation of federal law a crime in some instances, it cannot do so in a field (like the field of alien registration) that has been occupied by federal law. See California v. Zook , 336 U. S. 725, 730– 731, 733 (1949); see also In re Loney , 134 U. S. 372, 375– 376 (1890) (States may not impose their own punishment for perjury in federal courts).Arizona contends that §3 can survive preemption because the provision has the same aim as federal law and adopts its substantive standards. This argument not only ignores the basic premise of field preemption—that Statesmay not enter, in any respect, an area the Federal Government has reserved for itself—but also is unpersuasive11 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

on its own terms. Permitting the State to impose its own penalties for the federal offens es here would conflict with the careful framework Congress adopted. Cf. Buckman
Co. v. Plaintiffs’ Legal Comm. , 531 U. S. 341, 347–348 (2001) (States may not impose their own punishment for fraud on the Food and Drug Administration); Wisconsin Dept., supra, at 288 (States may not impose their own punishment for repeat violations of the National Labor Relations Act). Were §3 to come into force, the State would have the power to bring criminal charges againstindividuals for violating a federal law even in circumstances where federal officials in charge of the comprehensive scheme determine that prosecution would frustrate federal policies. There is a further intrusion upon the federal scheme.Even where federal authorities believe prosecution is appropriate, there is an inconsistency between §3 and federal law with respect to penalties. Under federal law, the failure to carry registrati on papers is a misdemeanor that may be punished by a fine, imprisonment, or a term of probation. See 8 U. S. C. §1304(e) (2006 ed.); 18 U. S. C. §3561. State law, by contrast, rules out probation as a possible sentence (and also eliminates the possibility of a pardon). See Ariz. Rev. Stat. Ann. §13–1509(D) (West Supp. 2011). This state framework of sanctions creates a conflict with the plan Congress put in place. See Wiscon

sin Dept.

, supra, at 286 (“[C]onflict is imminent whenever two separate remedies are brought to bear on the same activity” (internal quotation marks omitted)). These specific conflicts between state and federal law simply underscore the reason for field preemption. As it

did in Hines , the Court now concludes that, with respect to the subject of alien registration, Congress intended to preclude States from “complement[ing] the federal law, or enforc[ing] additional or auxiliary regulations.” 312 U. S., at 66–67. Section 3 is preempted by federal law.12 ARIZONA v. UNITED STATES

Opinion of the Court

B Section 5(C)
Unlike §3, which replicates federal statutory requirements, §5(C) enacts a state criminal prohibition where no federal counterpart exists. The provision makes it a statemisdemeanor for “an unauthorized alien to knowingly apply for work, solicit work in a public place or performwork as an employee or independent contractor” in Arizona. Ariz. Rev. Stat. Ann. §13–2928(C) (West Supp. 2011).Violations can be punished by a $2,500 fine and incarceration for up to six months. See §13–2928(F); see also §§13–707(A)(1) (West 2010); 13–802(A); 13–902(A)(5). The
United States contends that the provision upsets the balance struck by the Immigration Reform and Control Act of 1986 (IRCA) and must be preempted as an obstacle to the federal plan of regulation and control. When there was no comprehensive federal program regulating the employment of unauthorized aliens, this Court found that a State had authority to pass its own laws on the subject. In 1971, for example, California passed a law imposing civil penalties on the employment
of aliens who were “not entitl ed to lawful residence in the United States if such employment would have an adverse
effect on lawful resident workers.” 1971 Cal. Stats. ch. 1442, §1(a). The law was upheld against a preemption challenge in De Canas v. Bica , 424 U. S. 351 (1976). De
Canas recognized that “States possess broad authority under their police powers to regulate the employment relationship to protect workers within the State.” Id., at

356. At that point, however, the Federal Government had expressed no more than “a pe ripheral concern with [the] employment of illegal entrants.” Id. , at 360; see Whiting

, 563 U. S., at ___ (slip op., at 3). Current federal law is substantially different from the regime that prevailed when De Canas was decided. Congress enacted IRCA as a comprehensive framework forCite as: 567 U. S. ____ (2012) 13

Opinion of the Court

“combating the employment of illegal aliens.” Hoffman Plastic Compounds, Inc. v. NLRB , 535 U. S. 137, 147(2002). The law makes it illegal for employers to knowingly hire, recruit, refer, or continue to employ unauthorized workers. See 8 U. S. C. §§1324a(a)(1)(A), (a)(2). It alsorequires every employer to verify the employment authorization status of prospective employees. See §§1324a(a) (1)(B), (b); 8 CFR §274a.2(b) (2012). These requirementsare enforced through criminal penalties and an escalating series of civil penalties tied to the number of times an employer has violated the provisions. See 8 U. S. C. §§1324a(e)(4), (f); 8 CFR §274a.10. This comprehensive framework does not impose federal criminal sanctions on the employee side ( i.e., penalties on aliens who seek or engage in unauthorized work). Under federal law some civil penalties are imposed instead. Withcertain exceptions, aliens who accept unlawful employment are not eligible to hav e their status adjusted to that of a lawful permanent resident. See 8 U. S. C. §§1255(c)(2), (c)(8). Aliens also may be removed from the country for having engaged in unauthorized work. See§1227(a)(1)(C)(i); 8 CFR §214.1(e). In addition to specifying these civil consequences, federal law makes it a crime for unauthorized workers to obtain employment through fraudulent means. See 18 U. S. C. §1546(b). Congress has made clear, however, that any information employees submit to indicate their work status “may not be used” for purposes other than prosecution under specified federal criminal statutes for fraud, perjury, and related conduct. See 8 U. S. C. §§1324a(b)(5), (d)(2)(F)–(G). The legislative background of IRCA underscores the fact that Congress made a deliberate choice not to impose criminal penalties on aliens who seek, or engage in, unauthorized employment. A commission established by Congressto study immigration policy and to make recommendations concluded these penalties would be “unnecessary ­14 ARIZONA v. UNITED STATES

Opinion of the Court

and unworkable.” U. S. Immigration Policy and the National Interest: The Final Re port and Recommendations of the Select Commission on Immigration and Refugee Policy with Supplemental Views by Commissioners 65–66 (1981); see Pub. L. 95–412, §4, 92 Stat. 907. Proposals to make
unauthorized work a criminal offense were debated and discussed during the long process of drafting IRCA. See Brief for Service Employees International Union et al. as
Amici Curiae 9–12. But Congress rejected them. See, e.g., 119 Cong. Rec. 14184 (1973) (statement of Rep. Dennis).In the end, IRCA’s framework reflects a considered judgment that making criminals out of aliens engaged in

unauthorized work—aliens who already face the possibility of employer exploitation because of their removablestatus—would be inconsistent with federal policy and objectives. See, e.g., Hearings before the Subcommittee No. 1 of the House Committee on the Judiciary, 92d Cong., 1st Sess., pt. 3, pp. 919–920 (1971) (statement of Rep. Rodino, the eventual sponsor of IRCA in the House of Representatives). IRCA’s express preemption provision, which in mostinstances bars States from imposing penalties on employers of unauthorized aliens, is silent about whether additional penalties may be imposed against the employees themselves. See 8 U. S. C. §1324a(h)(2); Whiting, supra,at ___–___ (slip op., at 1–2). But the existence of an “express pre-emption provisio[n] does not bar the ordinary working of conflict pre-emption principles” or impose a “special burden” that would make it more difficult to establish the preemption of laws falling outside the clause.
Geier v. American Honda Motor Co. , 529 U. S. 861, 869– 872 (2000); see Sprietsma v. Mercury Marine , 537 U. S. 51, 65 (2002).The ordinary principles of preemption include the wellsettled proposition that a stat e law is preempted where it “stands as an obstacle to the accomplishment and exe­15 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

cution of the full purposes and objectives of Congress.”

Hines , 312 U. S., at 67. Under §5(C) of S. B. 1070, Arizona law would interfere with the careful balance struck by Congress with respect to unauthorized employment of aliens. Although §5(C) attempts to achieve one of the same goals as federal law—the deterrence of unlawfulemployment—it involves a conflict in the method of enforcement. The Court has recognized that a “[c]onflictin technique can be fully as disruptive to the system Congress enacted as conflict in overt policy.” Motor Coach Employees v. Lockridge , 403 U. S. 274, 287 (1971). The correct instruction to draw from the text, structure, and history of IRCA is that Cong ress decided it would be inappropriate to impose criminal penalties on aliens who seek or engage in unauthorized employment. It follows that a state law to the contrary is an obstacle to the regulatory system Congress chose. See Puerto Rico Dept. of Con

sumer Affairs v. ISLA Petroleum Corp. , 485 U. S. 495, 503 (1988) (“Where a comprehensiv e federal scheme intentionally leaves a portion of the regulated field without controls, then the pre-emptive inference can be drawn—not from federal inaction alone, but from inaction joined with action”). Section 5(C) is preempted by federal law.

C
Section 6
Section 6 of S. B. 1070 provides that a state officer, “without a warrant, may arrest a person if the officer has probable cause to believe . . . [the person] has committed any public offense that makes [him] removable from the United States.” Ariz. Rev. Stat. Ann. §13–3883(A)(5) (West Supp. 2011). The United States argues that arrests authorized by this statute would be an obstacle to the removal system Congress created. As a general rule, it is not a crime for a removable alien to remain present in the United States. See INS v. Lopez

-16 ARIZONA v. UNITED STATES

Opinion of the Court

Mendoza , 468 U. S. 1032, 1038 (1984). If the police stopsomeone based on nothing more than possible removability, the usual predicate for an arrest is absent. When an alien is suspected of being removable, a federal official

issues an administrative docu ment called a Notice to Ap

pear. See 8 U. S. C. §1229(a); 8 CFR §239.1(a) (2012). The form does not authorize an arrest. Instead, it gives the alien information about the proceedings, including the time and date of the removal hearing. See 8 U. S. C. §1229(a)(1). If an alien fails to appear, an in absentia order may direct removal. §1229a(5)(A).The federal statutory structure instructs when it is appropriate to arrest an alien during the removal process. For example, the Attorney General can exercise discretion
to issue a warrant for an alien’s arrest and detention “pending a decision on whether the alien is to be removedfrom the United States.” 8 U. S. C. §1226(a); see Memorandum from John Morton, Director, ICE, to All Field Office Directors et al., Exerci sing Prosecutorial DiscretionConsistent with the Civil Immigration Enforcement Priorities of the Agency for the Apprehension, Detention, and Removal of Aliens (June 17, 2011) (hereinafter 2011 ICE Memorandum) (describing facto rs informing this and related decisions). And if an a lien is ordered removed after a hearing, the Attorney General will issue a warrant. See 8 CFR §241.2(a)(1). In both instances, the warrants are executed by federal officers who have received training in the enforcement of immigration law. See §§241.2(b), 287.5(e)(3). If no federal warrant has been issued, those officers have more limited authority. See 8 U. S. C. §1357(a). They may arrest an alien for being “in the UnitedStates in violation of any [immigration] law or regulation,” for example, but only where the alien “is likely to escape before a warrant can be obtained.” §1357(a)(2). Section 6 attempts to provide state officers even greater authority to arrest aliens on the basis of possible remova­17 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

bility than Congress has given to trained federal immigration officers. Under stat e law, officers who believe an alien is removable by reason of some “public offense” would have the power to conduct an arrest on that basis regardless of whether a federal warrant has issued or the alien is likely to escape. This state authority could be exercised without any input from the Federal Government about whether an arrest is warranted in a particular case.This would allow the State to achieve its own immigration policy. The result could be unnecessary harassment of some aliens (for instance, a veteran, college student, or someone assisting with a criminal investigation) whom
federal officials determine should not be removed. This is not the system Congress created. Federal law specifies limited circumstances in which state officers mayperform the functions of an immigration officer. A principal example is when the Attorney General has granted that authority to specific o fficers in a formal agreement with a state or local government. See §1357(g)(1); see also §1103(a)(10) (authority may be extended in the event of an
“imminent mass influx of aliens off the coast of the UnitedStates”); §1252c (authority to arrest in specific circumstance after consultation with the Federal Government); §1324(c) (authority to arrest for bringing in and harboring certain aliens). Officers co vered by these agreements are subject to the Attorney Gene ral’s direction and super

vision. §1357(g)(3). There are significant complexities involved in enforcing federal immigration law, including the determination whether a person is removable. See

Padilla v. Kentucky , 559 U. S. ___, ___–___ (2010) (A LITO

, J., concurring in judgment) (slip op., at 4–7). As a result, the agreements reached with the Attorney General must
contain written certification that officers have receivedadequate training to carry out the duties of an immigration officer. See §1357(g)(2); cf. 8 CFR §§287.5(c) (arrest power contingent on training), 287.1(g) (defining the18 ARIZONA v. UNITED STATES

Opinion of the Court

training). By authorizing state officers to decide whether an alien should be detained for being removable, §6 violates the principle that the removal process is entrusted to the discretion of the Federal Government. See, e.g., Reno v. American-Arab Anti-Discrimination Comm., 525 U. S. 471,483–484 (1999); see also Brief for Former INS Commissioners 8–13. A decision on removability requires a determination whether it is appropriate to allow a foreign national to continue living in the United States. Decisions of this nature touch on foreign relations and must be made
with one voice. See Jama v. Immigration and Customs Enforcement , 543 U. S. 335, 348 (2005) (“Removal decisions, including the selection of a removed alien’s destination, may implicate [the Nation’s] relations with foreign powers and require consideration of changing political andeconomic circumstances” (internal quotation marks omitted)); see also Galvan v. Press , 347 U. S. 522, 531 (1954) (“Policies pertaining to the entry of aliens and their right to remain here are . . . entrusted exclusively to Congress . . .”); Truax v. Raich , 239 U. S. 33, 42 (1915) (“The authority to control immigration—to admit or exclude aliens—is vested solely in the Federal Government”).In defense of §6, Arizona notes a federal statute permitting state officers to “cooperate with the Attorney General in the identification, apprehension, detention, or removal of aliens not lawfully present in the United States.” 8

U. S. C. §1357(g)(10)(B). There may be some ambiguity as to what constitutes cooperatio n under the federal law; but no coherent understanding of the term would incorporate
the unilateral decision of stat e officers to arrest an alien for being removable absent any request, approval, or otherinstruction from the Federal Government. The Department of Homeland Security gives examples of what would constitute cooperation under federal law. These include situations where States participate in a joint task force19 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

with federal officers, provid e operational support in executing a warrant, or allow federal immigration officials to gain access to detainees held in state facilities. See Dept. of Homeland Security, Guidance on State and Local Governments’ Assistance in Immigration Enforcement and Related Matters 13–14 (2011), online at http:// www.dhs.gov/files/resources/immigration.shtm (all Inter

net materials as visited June 21, 2012, and available in Clerk of Court’s case file). State officials can also assist the Federal Government by responding to requests for
information about when an alien will be released from their custody. See §1357(d). But the unilateral state action to detain authorized by §6 goes far beyond these measures, defeating any need for real cooperation.Congress has put in place a system in which state officers may not make warrantless arrests of aliens based on possible removability except in specific, limited circumstances. By nonetheless authorizing state and local officers to engage in these enforce ment activities as a general matter, §6 creates an obstacle to the full purposes and objectives of Congress. See Hines , 312 U. S., at 67. Section 6 is preempted by federal law.

D Section 2(B)
Section 2(B) of S. B. 1070 requires state officers to make a “reasonable attempt . . . to determine the immigration status” of any person they stop, detain, or arrest on some other legitimate basis if “reasonable suspicion exists that the person is an alien and is unlawfully present in the United States.” Ariz. Rev. Stat. Ann. §11–1051(B) (West 2012). The law also provides that “[a]ny person who isarrested shall have the person’s immigration status determined before the person is released.” Ibid. The accepted way to perform these status checks is to contact ICE, which maintains a database of immigration records.20 ARIZONA v. UNITED STATES

Opinion of the Court

Three limits are built into the state provision. First, a detainee is presumed not to be an alien unlawfully present
in the United States if he or she provides a valid Arizona driver’s license or similar identification. Second, officers “may not consider race, color or national origin . . . exceptto the extent permitted by the United States [and] Arizona Constitution[s].” Ibid. Third, the provisions must be “implemented in a manner consistent with federal law regulating immigration, protecting the civil rights of all persons and respecting the privileges and immunities of United States citizens.” §11–1051(L) (West 2012).
The United States and its amici contend that, even with these limits, the State’s verifi cation requirements pose an obstacle to the framework Congress put in place. The first concern is the mandatory nature of the status checks. The second is the possibility of prolonged detention while the checks are being performed.

1

Consultation between federal and state officials is an important feature of the immi gration system. Congresshas made clear that no formal agreement or special training needs to be in place for state officers to “communicate with the [Federal Government] regarding the immigration status of any individual, in cluding reporting knowledge that a particular alien is not lawfully present in the United States.” 8 U. S. C. §1357(g)(10)(A). And Congress has obligated ICE to respond to any request made by state
officials for verification of a person’s citizenship or immigration status. See §1373(c); see also §1226(d)(1)(A) (requiring a system for determining whether individuals arrested for aggravated felonies are aliens). ICE’s Law Enforcement Support Center operates “24 hours a day, seven days a week, 365 days a year” and provides, among other things, “immigration status, identity information and real-time assistance to local, state and federal law21 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

enforcement agencies.” ICE, Fact Sheet: Law Enforcement Support Center (May 29, 2012), online at http:// www.ice.gov/news/library/factsheets/lesc.htm . LESC re sponded to more than one million requests for information in 2009 alone. App. 93.The United States argues that making status verification mandatory interferes with the federal immigration scheme. It is true that §2(B) does not allow state officers
to consider federal enforceme nt priorities in decidingwhether to contact ICE about someone they have detained. See Brief for United States 47–50. In other words, the officers must make an inquiry even in cases where it seems unlikely that the Attorney General would have the alien removed. This might be the case, for example, when an alien is an elderly ve teran with significant andlongstanding ties to the community. See 2011 ICE Memorandum 4–5 (mentioning these factors as relevant). Congress has done nothing to suggest it is inappropriate
to communicate with ICE in these situations, however. Indeed, it has encouraged the sharing of information about possible immigration violations. See 8 U. S. C. §1357(g) (10)(A). A federal statute regulating the public benefits provided to qualified aliens in fact instructs that “no State or local government entity may be prohibited, or in any way restricted, from sending to or receiving from [ICE] information regarding the immigration status, lawful or unlawful, of an alien in the United States.” §1644. The
federal scheme thus leaves room for a policy requiring
state officials to contact ICE as a routine matter. Cf. Whiting , 563 U. S., at ___–___ (slip op., at 23–24) (rejecting argument that federal law preempted Arizona’s requirement that employers determine whether employees were eligible to work throug h the federal E-Verify system where the Federal Government had encouraged its use). ­22 ARIZONA v. UNITED STATES

Opinion of the Court

2
Some who support the challenge to §2(B) argue that, in practice, state officers will be required to delay the release of some detainees for no reason other than to verify their immigration status. See, e.g., Brief for Former Arizona Attorney General Terry Goddard et al. as Amici Curiae 37,

n. 49. Detaining individuals solely to verify their immigration status would raise constitutional concerns. See,

e.g. , Arizona v. Johnson , 555 U. S. 323, 333 (2009); Illinois

v. Caballes , 543 U. S. 405, 407 (2005) (“A seizure that is justified solely by the interest in issuing a warning ticket to the driver can become unlawful if it is prolonged beyond the time reasonably required to complete that mission”). And it would disrupt the federal framework to put state officers in the position of holding aliens in custody for possible unlawful presence without federal direction and supervision. Cf. Part IV–C, supra (concluding that Arizona may not authorize warrantless arrests on the basis of removability). The program put in place by Congress does
not allow state or local office rs to adopt this enforcement

mechanism. But §2(B) could be read to avoid these concerns. To take one example, a person might be stopped for jaywalking in Tucson and be unable to produce identification. The first sentence of §2(B) instructs o fficers to make a “reasonable” attempt to verify his immigrat ion status with ICE if there is reasonable suspicion that his presence in the United States is unlawful. The state courts may conclude that, unless the person continues to be suspected of some crime for which he may be detained by state officers, it would not be reasonable to prolong the stop for the immigration inquiry. See Reply Brief for Petitioners 12, n. 4 (“[Section 2(B)] does not require the veri fication be completed duringthe stop or detention if that is not reasonable or practicable”); cf. Muehler v. Mena , 544 U. S. 93, 101 (2005) (finding no Fourth Amendment violation where questioning about23 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

immigration status did not prolong a stop).To take another example, a person might be held pending release on a charge of driving under the influence of alcohol. As this goes beyond a mere stop, the arrestee (unlike the jaywalker) would ap pear to be subject to the categorical requirement in the second sentence of §2(B) that “[a]ny person who is arrested shall have the person’s immigration status determined before [he] is released.” State courts may read this as an instruction to initiate a status check every time someone is arrested, or in some subset of those cases, rather than as a command to holdthe person until the check is complete no matter the circumstances. Even if the law is read as an instruction to complete a check while the person is in custody, moreover, it is not clear at this stage and on this record that the verification process would result in prolonged detention. However the law is interpre ted, if §2(B) only requires state officers to conduct a status check during the course of an authorized, lawful detention or after a detainee hasbeen released, the provision likely would survive preemption—at least absent some showing that it has otherconsequences that are adverse to federal law and its objectives. There is no need in this case to address whetherreasonable suspicion of illegal entry or another immigration crime would be a legiti mate basis for prolonging a detention, or whether this too would be preempted by federal law. See, e.g., United States v. Di Re , 332 U. S. 581, 589 (1948) (authority of state officers to make arrests for federal crimes is, absent federal statutory instruction, a matter of state law); Gonzales v. Peoria , 722 F. 2d 468, 475–476 (CA9 1983) (concluding that Arizona officers have authority to enforce the criminal provisions of federal immigration law), overruled on other grounds in HodgersDurgin v. de la Vina , 199 F. 3d 1037 (CA9 1999). The nature and timing of this case counsel caution in evaluating the validity of §2(B). The Federal Government24 ARIZONA v. UNITED STATES

Opinion of the Court

has brought suit against a sovereign State to challenge the provision even before the law has gone into effect. There is a basic uncertainty about what the law means and how it will be enforced. At this stage, without the benefit of a definitive interpretation from the state courts, it would be inappropriate to assume §2(B) will be construed in a way
that creates a conflict with federal law. Cf. Fox v. Wash

ington , 236 U. S. 273, 277 (1915) (“So far as statutes fairlymay be construed in such a way as to avoid doubtful constitutional questions they should be so construed; and it is to be presumed that state laws will be construed in that way by the state courts” (citation omitted)). As a result, the United States cannot preva il in its current challenge.
See Huron Portland Cement Co. v. Detroit , 362 U. S. 440, 446 (1960) (“To hold otherwise would be to ignore the teaching of this Court’s decisions which enjoin seeking out conflicts between state and federal regulation where none clearly exists”). This opinion does not foreclose other preemption and constitutional challenges to the law as interpreted and applied after it goes into effect.

V
Immigration policy shapes the destiny of the Nation.On May 24, 2012, at one of this Nation’s most distinguished museums of history, a dozen immigrants stood before the tattered flag that inspired Francis Scott Key to write the National Anthem. There they took the oath to become American citizens. The Smithsonian, News Release, Smithsonian Citizenship Ceremony Welcomes a Dozen New Americans (May 24, 2012), online at http://newsdesk.si.edu/releases . These naturalization ceremonies bring together men and women of different origins who now share a common destiny. They swear a common oath to renounce fidelity to foreign princes, to defend the Constitution, and to bear arms on behalf of the country when required by law. 8 CFR §337.1(a) (2012).25 Cite as: 567 U. S. ____ (2012)

Opinion of the Court

The history of the United States is in part made of the stories, talents, and lasting contributions of those who

crossed oceans and deserts to come here. The National Government has significant power to regulate immigration. With power comes responsibility, and the sound exercise of national power over immigration depends on the Nation’s meeting its responsibility to baseits laws on a political will informed by searching, thoughtful, rational civic discourse. Arizona may have understandable frustrations with the problems caused by illegal immigration while that process continues, but the State may not pursue policies that undermine federal law.

* * *
The United States has established that §§3, 5(C), and 6 of S. B. 1070 are preempted. It was improper, however, to enjoin §2(B) before the state courts had an opportunity to construe it and without some showing that enforcement of the provision in fact conflicts with federal immigration law and its objectives. The judgment of the Court of Appeals for the Ninth Circuit is affirmed in part and reversed in part. The case is remanded for further proceedings consistent with this opinion.

It is so ordered.

J USTICE K AGAN took no part in the consideration or
decision of this case._________________

_________________ Cite as: 567 U. S. ____ (2012) 1

Opinion of S CALIA

, J.



## SUPREME COURT OF THE UNITED STATES

No. 11–182

ARIZONA, ET AL ., PETITIONERS v. UNITED STATES

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF

APPEALS FOR THE NINTH CIRCUIT

[June 25, 2012]

J USTICE S CALIA , concurring in part and dissenting in
part.
The United States is an indivisible “Union of sovereign
States.” Hinderlider v. La Plata River & Cherry Creek
Ditch Co. , 304 U. S. 92, 104 (1938). Today’s opinion, approving virtually all of the Ninth Circuit’s injunction against enforcement of the four challenged provisions ofArizona’s law, deprives States of what most would consider the defining characterist ic of sovereignty: the power to exclude from the sovereign’s territory people who have no right to be there. Neithe r the Constitution itself nor even any law passed by Congress supports this result. I

dissent.

I
As a sovereign, Arizona has the inherent power to exclude persons from its territory, subject only to thoselimitations expressed in the Constitution or constitutionally imposed by Congress. That power to exclude has long been recognized as inherent in sovereignty. Emer de
Vattel’s seminal 1758 treatise on the Law of Nations

stated:

“The sovereign may forbid the entrance of his territory either to foreigners in general, or in particular cases, or to certain persons, or for certain particular purposes, according as he may think it advantageous to2 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

the state. There is nothing in all this, that does not flow from the rights of domain and sovereignty: every one is obliged to pay respect to the prohibition; and whoever dares violate it, incurs the penalty decreed to render it effectual.” The Law of Nations, bk. II, ch. VII, §94, p. 309 (B. Kapossy & R. Whatmore eds. 2008).

See also I R. Phillimore, Co mmentaries upon International Law, pt. III, ch. X, p. 233 (1854) (“It is a received maxim of International Law that, the Government of a State may prohibit the entrance of strangers into the country”). 1There is no doubt that “before the adoption of the constitution of the United States” each State had the authority to “prevent [itself] from being burdened by an influx of persons.” Mayor of New York v. Miln , 11 Pet. 102, 132– 133 (1837). And the Constitution did not strip the Statesof that authority. To the contrary, two of the Constitution’s provisions were design ed to enable the States to prevent “the intrusion of obnoxious aliens through other States.” Letter from James Madison to Edmund Randolph (Aug. 27, 1782), in 1 The Writings of James Madison 226 (1900); accord, The Federalist No. 42, pp. 269–271 (C. Rossiter ed. 1961) (J. Madison). The Articles of Confeder­

——————

1 Many of the 17th-, 18th-, and 19th-century commentators maintained that states should exclude foreigners only for good reason. Pufendorf, for example, maintained that states are generally expected to grant “permanent settlement to strangers who have been driven from their former home,” though ac knowledging that, when faced with the prospect of mass immigration, “every state may decide after its own custom what privilege should be granted in such a situation.” 2 Of the Law of Nature and Nations, bk. III, ch. III, §10, p. 366 (C. Oldfather &

W. Oldfather eds. 1934). See genera lly Cleveland, Powers Inherent in Sovereignty: Indians, Aliens, Terri tories, and the Nineteenth Century Origins of Plenary Power over Foreig n Affairs, 81 Tex. L. Rev. 1, 83–87 (2002). But the authority to exclude was universally accepted as inherent in sovereignty, whatever pr udential limitations there might be

on its exercise.3 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

ation had provided that “the free inhabitants of each ofthese States, paupers, vagabonds and fugitives from justice excepted, shall be entitled to all privileges and immunities of free citizens in the several States.” Articles of Confederation, Art. IV. This meant that an unwelcome alien could obtain all the rights of a citizen of one State simply by first becoming an inhabitant of another. To remedy this, the Constitution’s Privileges and Immunities Clause provided that “[t]he Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.” Art. IV, §2, cl. 1 (emphasis added). But if one State had particularly lax citizenship standards, it might still serve as a gateway for the entry of “obnoxious aliens” into other States. This problem was solved “by authorizing the general govern ment to establish a uniform rule of naturalization througho ut the United States.” The Federalist No. 42, supra, at 271; see Art. I, §8, cl. 4. In other words, the naturalizat ion power was given to Congress not to abrogate States’ power to exclude those they did not want, but to vindicate it.Two other provisions of the Constitution are an acknowledgment of the States’ so vereign interest in protecting their borders. Article I pr ovides that “[n]o State shall, without the Consent of the Congress, lay any Imposts or Duties on Imports or Exports, except what may be absolutely necessary for executing it’s inspection Laws .” Art. I, §10, cl. 2 (emphasis added). This assumed what everyone assumed: that the States could exclude from their territory dangerous or unwholesome goods. A later portion of the same section 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 .” Art. I, §10, cl. 3 (emphasis added). This limits the States’ sovereignty (in a way not relevant here) but leaves intact their inherent power to protect their territory. Notwithstanding “[t]he myth of an era of unrestricted4 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

immigration” in the first 100 years of the Republic, theStates enacted numerous laws restricting the immigration of certain classes of al iens, including convicted crimi

nals, indigents, persons with contagious diseases, and (in Southern States) freed blacks. Neuman, The Lost Century of American Immigration (1776–1875), 93 Colum. L. Rev.1833, 1835, 1841–1880 (1993). State laws not only provided for the removal of unwanted immigrants but also imposed penalties on unlawfully present aliens and those who aided their immigration. 2 Id., at 1883. In fact, the controversy surrounding the Alien and Sedition Acts involved a debate over whether, under the Constitution, the States had exclusive authority to enact such immigration laws. Criticism of the Sedition Act has become a prominent feature of our First Amendment jurisprudence, see, e.g., New York Times Co. v. Sullivan

, 376 U. S. 254, 273–276 (1964), but one of the Alien Acts 3 also aroused controversy at the time:

“ Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled , That it shall be lawful for the President of the United States at any time during the continuance of this act, to order all such aliens as he shall judge dangerous to the peace and safety of the United States, or shall have reasonable grounds to suspectare concerned in any treasonable or secret machinations against the government thereof, to depart out ofthe territory of the United States . . . .” An Act concerning Aliens, 1 Stat. 570, 570–571.

——————

2 E.g., Va. Code Tit. 54, ch. 198, §39 (1849) (“If a master of a vessel or other person, knowingly, import or br ing into this state, from any place
out of the United States , any person convicted of crime . . . he shall be confined in jail for three months, and be fined one hundred dollars”).

3 There were two Alien Acts, one of which dealt only with enemy aliens. An Act respecting Alien Enemies, 1 Stat. 577.5 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

The Kentucky and Virginia Resolutions, written in denunciation of these Acts, insisted that the power to exclude unwanted aliens rested solely in the States. Jefferson’s Kentucky Resolutions insisted “that alien friends are under the jurisdiction and protection of the laws of the state wherein they are [and] that no power over them has been delegated to the United States, nor prohibited tothe individual states, distinct from their power over citizens.” Kentucky Resolutions of 1798, reprinted in J. Powell, Languages of Power: A Sou rcebook of Early American Constitutional History 131 (1991). Madison’s VirginiaResolutions likewise contended that the Alien Act purported to give the President “a power nowhere delegated to the federal government.” Virginia Resolutions of 1798, reprinted in Powell, supra, at 134 (emphasis omitted). Notably, moreover, the Federalist proponents of the Act defended it primarily on the ground that “[t]he removal of aliens is the usual preliminary of hostility” and couldtherefore be justified in exercise of the Federal Government’s war powers. Massachussets Resolutions in Reply to Virginia, reprinted in Powell, supra, at 136.

In Mayor of New York v. Miln , this Court considered a New York statute that required the commander of any ship arriving in New York from abroad to disclose “the name, place of birth, and last legal settlement, age and occupation . . . of all passengers . . . with the intention of proceeding to the said city.” 11 Pet., at 130–131. After discussing the sovereign autho rity to regulate the entrance of foreigners described by De Vattel, the Court said:

“The power . . . of New York to pass this law havingundeniably existed at the formation of the constitution, the simply inquiry is, whether by that instrument it was taken from the states, and granted to congress; for if it were not, it yet remains with them.” Id., at 132.6 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

And the Court held that it remains. Id., at 139.

II

One would conclude from th e foregoing that after the adoption of the Constitution there was some doubt about the power of the Federal Gove rnment to control immigration, but no doubt about the power of the States to do so. Since the founding era (though not immediately), doubt
about the Federal Government ’s power has disappeared. Indeed, primary responsibility for immigration policy has
shifted from the States to the Federal Government. Congress exercised its power “[t]o establish an uniform Rule of Naturalization,” Art. I, §8, cl. 4, very early on, see An Act to establish an uniform Rule of Naturalization, 1 Stat.

103. But with the fleeting exception of the Alien Act, Congress did not enact any legislation regulating immigration for the better part of a century. In 1862, Congress passed “An Act to prohibit the ‘Coolie Trade’ by AmericanCitizens in American Vessels,” which prohibited “procuring [Chinese nationals] . . . to be disposed of, or sold, ortransferred, for any term of years or for any time whatever, as servants or apprentices, or to be held to service or labor.” 12 Stat. 340. Then, in 1875, Congress amended that act to bar admission to Chinese, Japanese, and other Asian immigrants who had “entered into a contract or agreement for a term of service within the United States, for lewd and immoral purposes.” An act supplementary to the acts in relation to immigration, ch. 141, 18 Stat. 477. And in 1882, Congress enacte d the first general immigration statute. See An act to regulate Immigration, 22 Stat. 214. Of course, it hardly bears mention that Federal immigration law is now extensive. I accept that as a valid exercise of federal power—not because of the Naturalization Clause (it has no necessary connection to citizenship) but because it is an inherent attribute of sovereignty no less for the United States than7 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

for the States. As this Court has said, 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.’ ” Fong Yue Ting v. United States

, 149 U. S. 698, 705 (1893) (quoting Ekiu v. United States

, 142 U. S. 651, 659 (1892)). That is why there was no needto set forth control of immigration as one of the enumerated powers of Congress, although an acknowledgment of that power (as well as of the States’ similar power, subject to federal abridgment) was contained in Art. I, §9, which provided that “[t]he Migration or Importation of such Persons as any of the States now existing shall think proper to admit, shall not be prohibited by the Congress prior to the Year one thousand eight hundred and eight . . . .” In light of the predominance of federal immigration restrictions in modern times, it is easy to lose sight of the States’ traditional role in regulating immigration—and to overlook their sovereign prerogat ive to do so. I accept as a given that State regulation is excluded by the Constitution when (1) it has been prohibited by a valid federal law, or (2) it conflicts with federal regulation—when, for example, it admits those whom federal regulation would exclude, or excludes those whom federal regulation would admit. Possibility (1) need not be considered here: there is no federal law prohibiting the St ates’ sovereign power to exclude (assuming federal authority to enact such a law). The mere existence of federal action in the immigration area—and the so-called field preemption arising from that action, upon which the Court’s opinion so heavily relies,

ante, at 9–11—cannot be regarded as such a prohibition. We are not talking here about a federal law prohibiting the States from regulating bubble-gum advertising, or
even the construction of nucle ar plants. We are talking about a federal law going to the core of state sovereignty:8 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

the power to exclude. Like elimination of the States’ other inherent sovereign power, im munity from suit, elimination of the States’ sovereign power to exclude requires that“Congress . . . unequivocally expres[s] its intent to abrogate,” Seminole Tribe of Fla. v. Florida , 517 U. S. 44, 55 (1996) (internal quotation marks and citation omitted). Implicit “field preemption” will not do. Nor can federal power over illegal immigration be deemed exclusive because of what the Court’s opinion solicitously calls “foreign countries[’] concern[s] about the status, safety, and security of their nationals in the United States,” ante , at 3. The Constitution gives all those on our shores the protections of the Bill of Rights—but just asthose rights are not expanded for foreign nationals because of their countries’ views (some countries, for example, have recently discovered the death penalty to be barbaric), neither are the fundamental sovereign powers of the States abridged to accommodate foreign countries’ views. Even in its international relations, the Federal
Government must live with the inconvenient fact that it isa Union of independent States, who have their own sovereign powers. This is not the first time it has found that a nuisance and a bother in the conduct of foreign policy. Four years ago, for example, the Government importuned us to interfere with thoroughly constitutional state judicialprocedures in the criminal trial of foreign nationals because the international community, and even an opinion of
the International Court of Jus tice, disapproved them. See

Medellín v. Texas , 552 U. S. 491 (2008). We rejected that request, as we should reject the Executive’s invocation of foreign-affairs considerations here. Though it may upset foreign powers—and even when the Federal Government desperately wants to avoid upsetting foreign powers—the States have the right to protect their borders against foreign nationals, just as they have the right to execute foreign nationals for murder.9 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

What this case comes down to, then, is whether the Arizona law conflicts with federal immigration law—

whether it excludes those wh om federal law would admit,
or admits those whom federal law would exclude. It does not purport to do so. It applies only to aliens who neither possess a privilege to be present under federal law nor have been removed pursuant to the Federal Government’s inherent authority. I proceed to consider the challenged provisions in detail.

§2(B)

“For any lawful stop, detention or arrest made by a law enforcement official . . . in the enforcement of any other law or ordinance of a county, city or town or thisstate where reasonable suspicion exists that the person is an alien and is unlawfully present in the United States, a reasonable attempt shall be made, when practicable, to determine the immigration status of the person, except if the determination may hinder or obstruct an investigation. Any person who is arrestedshall have the person’s immigration status determined before the person is released. . . .” S. B. 1070, §2(B), as amended

, Ariz. Rev. Stat. Ann. §11–1051(B) (West 2012).

The Government has conceded that “even before Section2 was enacted, state and local officers had state-law authority to inquire of DHS [t he Department of HomelandSecurity] about a suspect’s unlawful status and otherwise cooperate with federal immigration officers.” Brief for United States 47 (citing App. 62, 82); see also Brief forUnited States 48–49. That concession, in my view, obviates the need for further inquiry. The Government’s conflict-pre-emption claim calls on us “to determine whether, under the circumstances of this particular case

,[the State’s] law stands as an obstacle to the accomplishment and execution of the full purposes and objectives of10 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

Congress.” Hines v. Davidowitz , 312 U. S. 52, 67 (1941) (emphasis added). It is impossible to make such a finding without a factual record concerning the manner in which Arizona is implementing these provisions—something the Government’s pre-enforcement challenge has pretermitted. “The fact that [a law] might operate unconstitutionally
under some conceivable set of circumstances is insufficient to render it wholly invalid, since we have not recognized an ‘overbreadth’ doctrine outside the limited
context of the First Amendment.” United States v. Salerno , 481 U. S. 739, 745 (1987). And on its face, §2(B) merely tells state officials t hat they are authorized to do something that they were, by the Government’s concession, already authorized to do. The Court therefore properly rejects the Government’s challenge, recognizing that, “[a]t this stage, without the benefit of a definitive interpre tation from the state courts, it would be inappropriate to assume §2B will be construed in a way that creates a conflict with federal law.” Ante, at

23. Before reaching that co nclusion, however, the Court goes to great length to assuag e fears that “state officers will be required to delay the release of some detainees for no reason other than to verify their immigration status.” Ante, at 22. Of course, any investigatory detention, including one under §2(B), may become an “unreasonable . . . seizur[e],” U. S. Const., Amdt. IV, if it lasts too long.
See Illinois v. Caballes , 543 U. S. 405, 407 (2005). Butthat has nothing to do with this case, in which the Government claims that §2(B) is pre-empted by federal immigration law, not that anyone’s Fourth Amendment rights have been violated. And I know of no reason why a protracted detention that does not violate the Fourth
Amendment would contradict or conflict with any federal immigration law.11 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

§6

“A peace officer, without a warrant, may arrest a person if the officer has probable cause to believe . . . [t]he person to be arrested has committed any public offense that makes the person removable from the United States.” S. B. 1070, §6(A)(5), Ariz. Rev. Stat. Ann. §13–3883(A)(5) (West Supp. 2011).

This provision of S. B. 1070 expands the statutory list of offenses for which an Arizona police officer may make an arrest without a warrant. See §13–3883. If an officer has probable cause to believe that an individual is “removable”by reason of a public offense, then a warrant is not required to make an arrest. The Government’s primary contention is that §6 is pre-empted by federal immigration
law because it allows state officials to make arrests “without regard to federal priorities .” Brief for United States

53. The Court’s opinion focuses on limits that Congress has placed on federal officials’ authority to arrest removable aliens and the possibility that state officials will make arrests “to achieve [Arizona’s] own immigration policy” and “without any input from the Federal Government.” Ante, at 17. Of course on this pre-enforcement record there is no reason to assume that Arizona officials will ignore federal immigration policy (unless it be the questionable policy of not wanting to identify illegal aliens who have committed offenses that make them removable). As Arizona points out, federal law expressly provides that state officers may “cooperate with the Attorney General in the identification, apprehension, detention, or removal of aliens not lawfully present in the United States,” 8 U. S. C. §1357(g)(10)(B); and “cooperation” requires neither identical efforts nor prior federal approval. It is consistent with the Arizona statute, and with the “cooperat [ive]” system that Congress has created, for state officials to arrest a removable alien,12 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

contact federal immigration authorities, and follow their lead on what to do next. And it is an assault on logic to say that identifying a removable alien and holding him for
federal determination of whet her he should be removed “violates the principle that the removal process is entrusted to the discretion of the Federal Government,” ante, at

18. The State’s detention does not represent commencement of the removal process unless the Federal Government makes it so. But that is not the most important point. The most important point is that, as we have discussed, Arizona is

entitled to have “its own immigration policy”—including a more rigorous enforcement policy—so long as that does not conflict with federal law. The Court says, as though the point is utterly dispositive, that “it is not a crime for a removable alien to remain present in the United States,”

ante, at 15. It is not a federal crime, to be sure. But there
is no reason Arizona cannot make it a state crime for a removable alien (or any illegal alien, for that matter) to remain present in Arizona. The Court quotes 8 U. S. C. §1226(a), which provides that, “[o]n a warrant issued by the Attorney General, an alien may be arrested and detained pending a decision on
whether the alien is to be removed from the United States.” Section 1357(a)(2) also provides that a federal immigration official “shall have power without warrant . . . to arrest any alien in the United States, if he has reason to
believe that the alien so arrested is in the United States in violation of any [federal immigration] law or regulation and is likely to escape before a warrant can be obtained for his arrest.” But statutory limitations upon the actions of federal officers in enforcing the United States’ power to protect its borders do not on th eir face apply to the actions of state officers in enforcing the State’s power to protect its

borders. There is no more re ason to read these provisions as implying that state offici als are subject to similar limi­13 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

tations than there is to read them as implying that only federal officials may arrest re movable aliens. And in any

event neither implication would constitute the sort of clear
elimination of the States’ so vereign power that our cases

demand.The Court raises concerns about “unnecessary harassment of some aliens . . . wh om federal officials determine
should not be removed.” Ante, at 17. But we have no license to assume, without any support in the record, that Arizona officials would use their arrest authority under §6 to harass anyone. And it makes no difference that federal officials might “determine [that some unlawfully present aliens] should not be removed,” ibid. They may well determine not to remove from the United States aliens who have no right to be here; but unless and until these aliens have been given the right to remain, Arizona is entitled to

arrest them and at least bring them to federal officials’ attention, which is all that §6 necessarily entails. (In my view, the State can go further than this, and punish them for their unlawful entry and presence in Arizona.) The Government complains that state officials might notheed “federal priorities.” Indeed they might not, particularly if those priorities include willful blindness or deliberate inattention to the presence of removable aliens in Arizona. The State’s whole complaint—the reason this law was passed and this case has arisen—is that the
citizens of Arizona believe fede ral priorities are too lax. The State has the sovereign power to protect its borders more rigorously if it wishes, absent any valid federal prohibition. The Executive’s policy choice of lax federal enforcement does not constitute such a prohibition.

§3

“In addition to any violation of federal law, a person is guilty of willful failure to complete or carry an alien registration document if the person is in violation of 814 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

[U. S. C.] §1304(e) or §1306(a).” S. B. 1070, §3(A), as amended, Ariz. Rev. Stat. Ann. §13–1509(A).

It is beyond question that a State may make violation of
federal law a violation of state law as well. We have heldthat to be so even when the interest protected is a distinctively federal interest, such as protection of the dignity of the national flag, see Halter v. Nebraska , 205 U. S. 34 (1907), or protection of the Federal Government’s ability to recruit soldiers, Gilbert v. Minnesota , 254 U. S. 325 (1920). “[T]he State is not inhibited from making the national purposes its own purposes to the extent of exerting its police power to prevent its ow n citizens from obstructing the accomplishment of such purposes.” Id., at 331 (internal quotation marks omitted). Much more is that so when, as here, the State is protecting its own interest, the integrity of its borders. And we have said that explicitly withregard to illegal immigration: “Despite the exclusive federal control of this Nation’s borders, we cannot conclude that the States are without any power to deter the influx of persons entering the United States against federal law, and whose numbers might have a discernible impact on
traditional state concerns.” Plyler v. Doe , 457 U. S. 202, 228, n. 23 (1982). The Court’s opinion relies upon Hines v. Davidowitz

, supra. Ante , at 9–10. But that case did not, as the Court believes, establish a “field preemption” that implicitly eliminates the States’ sovereign power to exclude those
whom federal law excludes. It held that the States are not permitted to establish “additi onal or auxiliary” registration requirements for aliens. 312 U. S., at 66–67. But §3 does not establish additional or auxiliary registration requirements. It merely makes a violation of state law the

very same failure to register and failure to carry evidence of registration that are violations of federal law. Hines does not prevent the State from relying on the federal15 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

registration system as “an available aid in the enforcement of a number of statutes of the state applicable toaliens whose constitutional validity has not been questioned.” Id., at 75–76 (Stone, J., dissenting). One such statute is Arizona’s law forbidding illegal aliens to collect unemployment benefits, Ariz. Rev. Stat. Ann. §23–781(B) (West 2012). To enforce that and other laws that validly turn on alien status, Arizona has, in Justice Stone’s words, an interest in knowing “the number and whereabouts of aliens within the state” and in having “a means of their identification,” 312 U. S., at 75. And it can punish the aliens’ failure to comply with the provisions of federal law that make that knowledge and identification possible. In some areas of uniquely federal concern— e.g., fraud in a federal administrative process ( Buckman Co. v. Plaintiffs’ Legal Comm. , 531 U. S. 341 (2001)) or perjury in violation of a federally required oath ( In re Loney , 134
U. S. 372 (1890))—this Court has held that a State has no legitimate interest in enforcing a federal scheme. But the federal alien registration system is certainly not of uniquely federal interest. States, private entities, and individuals rely on the federal registration system (including theE-Verify program) on a regular basis. Arizona’s legitimate interest in protecting (among other things) its unemploymentbenefits system is an entirely adequate basis for making the violation of federal regi stration and carry requirements a violation of state law as well. The Court points out, however, ante, at 11, that in some respects the state law exceeds the punishments prescribed by federal law: It rules out probation and pardon, which
are available under federal law. The answer is that it makes no difference. Illegal immigrants who violate §3

violate Arizona law. It is one thing to say that the Supremacy Clause prevents Arizona law from excluding those whom federal law admits. It is quite something else to say that a violation of Arizona law cannot be punished16 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

more severely than a violation of federal law. Especially where (as here) the State is defending its own sovereign interests, there is no precedent for such a limitation. The sale of illegal drugs, for exam ple, ordinarily violates state law as well as federal law, and no one thinks that thestate penalties cannot exceed the federal. As I have discussed, moreover, “field pr eemption” cannot establish a prohibition of additional state penalties in the area of immigration. Finally, the Government also suggests that §3 poses an obstacle to the administration of federal immigration law,
see Brief for United States 31–33, but “there is no conflict in terms, and no possibility of such conflict, [if] the state statute makes federal law its own,” California v. Zook , 336
U. S. 725, 735 (1949). It holds no fear for me, as it does for the Court, that “[w]ere §3 to come into force, the State would have the power to bring criminal char ges against individuals forviolating a federal law even in circumstances where federal officials in charge of the comprehensive scheme determine that prosecution would frustrate federal policies.” Ante, at 11. That seems to me entirely appropriate when the State uses the federal law (as it must) as the criterion
for the exercise of its own power , and the implementation
of its own policies of excluding those who do not belong
there. What I do fear—and what Arizona and the States that support it fear—is that “federal policies” of nonen

forcement will leave the States helpless before those evil effects of illegal immigration that the Court’s opinion dutifully recites in its prologue ( ante, at 6) but leaves unremedied in its disposition.

§5(C)

“It is unlawful for a person who is unlawfully present
in the United States and who is an unauthorized alien to knowingly apply for work, solicit work in a public17 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

place or perform work as an employee or independent contractor in this state.” S. B. 1070, §5(C), as amended, Ariz. Rev. Stat. Ann. §13–2928(C).

Here, the Court rightly starts with De Canas v. Bica

, 424 U. S. 351 (1976), which involved a California law providing that “ ‘[n]o employer shall knowingly employ an
alien who is not entitled to lawful residence in the United States if such employment would have an adverse effect
on lawful resident workers.’ ” Id. , at 352 (quoting California Labor Code Ann. §2805(a)). This Court concluded that the California law was not pre-empted, as Congress had neither occupied the field of “regulation of employment ofillegal aliens” nor expressed “the clear and manifest purpose” of displacing such state regulation. Id., at 356–357 (internal quotation marks omitted). Thus, at the time
De Canas was decided, §5(C) would have been indubitably
lawful. The only relevant change is that Congress has since enacted its own restrictions on employers who hire illegal aliens, 8 U. S. C. §1324a, in legislation that also includes some civil (but no criminal) penalties on illegal aliens who accept unlawful employment. The Court concludes from this (reasonably enough) “that Congress made a deliberate choice not to impose criminal penalties on aliens who seek, or engage in, unauthorized employment,” ante , at 13. But that is not the same as a deliberate choice to prohibit the States from imposing criminal penalties. Congress’s intent with regard to exclus ion of state law need not be guessed at, but is found in the law’s express pre-emption provision, which excludes “any State or local law imposing civil or criminal sanctions (other than through licensing and similar laws) upon those who employ

, or recruit or refer for a fee for employment, unauthorized aliens,” §1324a(h)(2) (emphasis added). Common sense, reflected

in the canon expressio unius est exclusio alterius

, suggests18 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

that the specification of pre-emption for laws punishing “those who employ” implies the lack of pre-emption for other laws, including laws punishing “those who seek or accept employment.”
The Court has no credible re sponse to this. It quotesour jurisprudence to the effect that an “express preemption provisio[n] does not bar the ordinary working of conflict pre-emption principles.” Ante, at 14 (quoting Geier

v. American Honda Motor Co. , 529 U. S. 861, 869 (2000) (internal quotation marks omitted)). True enough— conflict preemption principles. It then goes on say thatsince “Congress decided it would be inappropriate to impose criminal penalties on aliens who seek or engage in unauthorized employment,” “[i]t follows that a state law tothe contrary is an obstacle to the regulatory system Congress chose.” Ante, at 15. For “ ‘[w]here a comprehensivefederal scheme intentionally leaves a portion of the regulated field without controls, then the pre-emptive inference
can be drawn.’ ” Ibid. (quoting Puerto Rico Dept. of Consumer Affairs v. ISLA Petroleum Corp. , 485 U.S. 495, 503 (1988)). All that is a classic description not of conflict pre-emption but of field pre-emption, which (concededly) does not occur beyond the terms of an express pre-emption provision. The Court concludes that §5(C) “would interfere with the careful balance struck by Congress,” ante, at 15, (another field pre-emption notion, by the way) but that is easy to say and impossible to demonstrate. The Court reliesprimarily on the fact that “[p]roposals to make unauthorized work a criminal offense were debated and discussedduring the long process of drafting [the Immigration Reform and Control Act of 1986 (IRCA)],” “[b]ut Congress rejected them.” Ante, at 14. There is no more reason to believe that this rejection was expressive of a desire that there be no sanctions on employees, than expressive of a
desire that such sanctions be left to the States. To tell the19 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

truth, it was most likely expressive of what inaction ordinarily expresses: nothing at all. It is a “naïve assumption that the failure of a bill to make it out of committee, or to be adopted when reported to the floor, is the same as a congressional rejection of what the bill contained.” Crosby v. National Foreign Trade Council , 530 U. S. 363, 389 (2000) (S CALIA , J., concurring in judgment) (internal quotation marks and alterations omitted).

* * *

The brief for the Government in this case asserted that “the Executive Branch’s ability to exercise discretion and set priorities is particularly important because of the need
to allocate scarce enforcement resources wisely.” Brief for United States 21. Of course there is no reason why the
Federal Executive’s need to allocate its scarce enforcement resources should disable Arizona from devoting its resources to illegal immigration in Arizona that in its view the Federal Executive has given short shrift. Despite Congress’s prescription that “the immigration laws of the United States should be enforced vigorously and uniformly,” IRCA §115, 100 Stat. 3384, Arizona asserts without contradiction and with supporting citations:

“[I]n the last decade federal enforcement efforts have focused primarily on areas in California and Texas, leaving Arizona’s border to suffer from comparativeneglect. The result has been the funneling of an increasing tide of illegal border crossings into Arizona.Indeed, over the past decade, over a third of the Nation’s illegal border crossings occurred in Arizona.” Brief for Petitioners 2–3 (footnote omitted).

Must Arizona’s ability to protect its borders yield to the reality that Congress has provided inadequate funding for federal enforcement—or, even worse, to the Executive’s unwise targeting of that funding?20 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

But leave that aside. It has become clear that federal enforcement priorities—in the sense of priorities based on
the need to allocate “scarce enforcement resources”—is not the problem here. After this case was argued and while it was under consideration, the Secretary of HomelandSecurity announced a program exempting from immigration enforcement some 1.4 million illegal immigrants under the age of 30. 4 If an individual unlawfully present
in the United States

“• came to the United States under the age of sixteen;

“• has continuously resided in the United States for at least five years . . . ,

“• is currently in school, has graduated from highschool, has obtained a general education development certificate, or is an honorably discharged
veteran . . . ,
“• has not been convicted of a [serious crime]; and

“• is not above the age of thirty,” 5

then U. S. immigration officials have been directed to “defe[r] action” against such individual “for a period of two years, subject to renewal.” 6 The husbanding of scarce enforcement resources can hardly be the justification forthis, since the considerable administrative cost of conducting as many as 1.4 million background checks, and ruling on the biennial requests for dispensation that the nonen­

——————

4 Preston & Cushman, Obama to Perm it Young Migrants to Remain in U. S., N. Y. Times, June 16, 2012, p. A1.

5 Memorandum from Janet Napolitano, Secretary of Homeland Security, to David V. Aguilar, Acting Commissioner, U. S. Customs and Border Protection; Alejandro Mayork as, Director, U. S. Citizenship and Immigration Services; and John Mo rton, Director, U. S. Immigration and Customs Enforcement, p. 1 (June 15, 2012), online at http://www.dhs.gov (all Internet materi als as visited June 22, 2012, and
available in Clerk of Court’s case file).

6 Id., at 2.21 Cite as: 567 U. S. ____ (2012)

Opinion of S CALIA

, J.

forcement program envisions, will necessarily be deducted from immigration enforcement. The President said at a news conference that the new program is “the right thingto do” in light of Congress’s failure to pass the Administration’s proposed revision of the Immigration Act. 7 Perhaps it is, though Arizona may not think so. But to say, as the Court does, that Arizona contradicts federal law by enforcing applications of the Immigr ation Act that the President declines to enforce boggles the mind.The Court opinion’s looming specter of inutterable horror—“[i]f §3 of the Arizona statute were valid, every State could give itself independent authority to prosecute federal registration violations,” ante, at 10—seems to me not so horrible and even less looming. But there has come to pass, and is with us today, the specter that Arizona andthe States that support it predicted: A Federal Government that does not want to enforce the immigration laws as written, and leaves the States’ borders unprotected against immigrants whom those laws would exclude. So the issue is a stark one. Are the sovereign States at the mercy of the Federal Executive’s refusal to enforce the Nation’s immigration laws? A good way of answering that question is to ask: Would the States conceivably have entered into the Union if the
Constitution itself contained the Court’s holding? Today’s judgment surely fails that test. At the Constitutional Convention of 1787, the delegates contended with “the jealousy of the states with re gard to their sovereignty.” 1 Records of the Federal Convention 19 (M. Farrand ed.1911) (statement of Edmund Randolph). Through ratification of the fundamental charter that the Convention produced, the States ceded much of their sovereignty to the
Federal Government. But much of it remained jealously

——————

7 Remarks by the President on Immigr ation (June 15, 2012), online at http://www.whitehouse.gov

.22 ARIZONA v. UNITED STATES

Opinion of S CALIA

, J.

guarded—as reflected in the innumerable proposals that never left Independence Hall. Now, imagine a provision—perhaps inserted right after Art. I, §8, cl. 4, the Naturalization Clause—which included among the enumeratedpowers of Congress “To establish Limitations upon Immigration that will be exclusiv e and that will be enforced only to the extent the President deems appropriate.” The delegates to the Grand Conven tion would have rushed to

the exits. As is often the case, discussion of the dry legalities that are the proper object of our attention suppresses the very human realities that gave rise to the suit. Arizona bears the brunt of the country’s illegal immigration problem. Its
citizens feel themselves under siege by large numbers of illegal immigrants who invade their property, strain their social services, and even place their lives in jeopardy. Federal officials have been unable to remedy the problem, and indeed have recently show n that they are unwilling to do so. Thousands of Arizona’s estimated 400,000 illegal immigrants—including not just children but men andwomen under 30—are now assured immunity from enforcement, and will be able to compete openly with Ari

zona citizens for employment. Arizona has moved to protect its sovereignty—not in contradiction of federal law, but in complete compliance with it. The laws under challenge here do not extend or revise federal immigration res trictions, but merely enforce those restrictions more effectively . If securing its territory
in this fashion is not within the power of Arizona, we should cease referring to it as a sovereign State. I dissent._________________

_________________ 1 Cite as: 567 U. S. ____ (2012)

Opinion of T HOMAS

, J.



## SUPREME COURT OF THE UNITED STATES

No. 11–182

ARIZONA, ET AL ., PETITIONERS v. UNITED STATES

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF

APPEALS FOR THE NINTH CIRCUIT

[June 25, 2012]

J USTICE T HOMAS , concurring in part and dissenting in
part.
I agree with J USTICE S CALIA that federal immigration law does not pre-empt any of the challenged provisions of
S. B. 1070. I reach that conclusion, however, for the sim

ple reason that there is no conflict between the “ordinary meanin[g]” of the relevant federal laws and that of the four provisions of Arizona law at issue here. Wyeth v. Levine , 555 U. S. 555, 588 (2009) (T HOMAS , J., concurring in judgment) (“Pre-emption analysis should not be a free

wheeling judicial inquiry into whether a state statute is in tension with federal objectives, but an inquiry into whether the ordinary meanings of state and federal law conflict” (brackets; internal quotation marks omitted)). Section 2(B) of S. B. 1070 provides that, when Arizona
law enforcement officers reas onably suspect that a person they have lawfully stopped, de tained, or arrested is unlaw

fully present, “a reasonable attempt shall be made, when practicable, to determine the immigration status of the person” pursuant to the verification procedure established by Congress in 8 U. S. C. §1373(c). Ariz. Rev. Stat. Ann. §11–1051(B) (West 2012). Nothing in the text of that or any other federal statute proh ibits Arizona from directing its officers to make immigration-related inquiries in these situations. To the contrary, federal law expressly states that “no State or local government entity may be prohib-2 ARIZONA v. UNITED STATES

Opinion of T HOMAS

, J.

ited, or in any way restricted, from sending to or receiving
from” federal officials “infor mation regarding the immigra

tion status” of an alien. 8 U. S. C. §1644. And, federal law imposes an affirmative obligation on federal officials to respond to a State’s immigration-related inquiries. §1373(c).
Section 6 of S. B. 1070 authorizes Arizona law enforce

ment officers to make warrantless arrests when there is probable cause to believe that an arrestee has committed a public offense that renders him removable under federal immigration law. States, as sovereigns, have inherent authority to conduct arrests fo r violations of federal law, unless and until Congress removes that authority. See
United States v. Di Re , 332 U. S. 581, 589 (1948) (holding that state law determines the validity of a warrantless
arrest for a violation of federal law “in the absence of an applicable federal statute”). Here, no federal statute purports to withdraw that authority. As J USTICE S CALIA notes, ante, at 12 (opinion concurring in part and dissent

ing in part), federal law does limit the authority of federal officials to arrest removable aliens, but those statutes do not apply to state officers. And, federal law expressly recognizes that state officers may “cooperate with the Attorney General” in the “apprehension” and “detention” of “aliens not lawfully present in the United States.” §1357(g)(10)(B). Nothing in that statute indicates that such cooperation requires a prior “request, approval, or
other instruction from the Federal Government.” Ante, at 18 (majority opinion).
Section 3 of S. B. 1070 makes it a crime under Arizona law for an unlawfully present alien to willfully fail to complete or carry an alien regi stration document in viola

tion of 8 U. S. C. §1304(e) and §1306(a). Section 3 simply incorporates federal registration standards. Unlike the Court, I would not hold that Congress pre-empted the field of enforcing those standards. “[O]ur recent cases have3 Cite as: 567 U. S. ____ (2012)

Opinion of T HOMAS

, J.

frequently rejected field pre-emption in the absence of statutory language expressly requiring it.” Camps New

found/Owatonna, Inc. v. Town of Harrison , 520 U. S. 564, 617 (1997) (T HOMAS

, J., dissenting); see, e.g., New York State Dept. of Social Servs. v. Dublino , 413 U. S. 405, 415 (1973). Here, nothing in the text of the relevant federal statutes indicates that Congress intended enforcement of its registration requirements to be exclusively the prov

ince of the Federal Government. That Congress created a “full set of standards governing alien registration,” ante, at 10 (majority opinion), merely indicates that it intended the scheme to be capable of working on its own, not that it wanted to preclude the States from enforcing the federal

standards. Hines v. Davidowitz , 312 U. S. 52 (1941), is not to the contrary. As J USTICE S CALIA explains, ante, at 14,
Hines at most holds that federa l law pre-empts the States from creating additional regi stration requirements. But here, Arizona is merely seeking to enforce the very regis

tration requirements that Congress created. Section 5(C) of S. B. 1070 prohibits unlawfully present aliens from knowingly applying for, soliciting, or perform

ing work in Arizona. Section 5(C) operates only on indi

viduals whom Congress has already declared ineligible to work in the United States. Nothing in the text of the federal immigration laws prohibits States from imposing their own criminal penalties on such individuals. Fed

eral law expressly pre-empts St ates from “imposing civil or criminal sanctions (other than through licensing and similar laws) upon those who employ , or recruit or refer for a fee for employment, unauthorized aliens.” 8 U. S. C. §1324a(h)(2) (emphasis added). But it leaves States free to impose criminal sanctions on the employees themselves. Despite the lack of any conflict between the ordinary meaning of the Arizona law and that of the federal laws at issue here, the Court holds that various provisions of the Arizona law are pre-empted because they “stan[d] as an4 ARIZONA v. UNITED STATES

Opinion of T HOMAS

, J.

obstacle to the accomplishment and execution of the full purposes and objectives of Congress.” Hines

, supra , at 67. I have explained that the “purposes and objectives” theory of implied pre-emption is inconsistent with the Constitu

tion because it invites courts to engage in freewheeling speculation about congressional purpose that roams well beyond statutory text. See Wyeth , 555 U. S., at 604 (opin

ion concurring in judgment); see also Williamson v. Mazda Motor of America, Inc. , 562 U. S. ___, ___–___ (2011) (opin

ion concurring in judgment) (slip op., at 2–3); Haywood v. Drown , 556 U. S. 729, 767 (2009) (dissenting opinion). Under the Supremacy Clause, pre-emptive effect is to be given to congressionally ena cted laws, not to judicially divined legislative purposes. See Wyeth

, supra , at 604 (T HOMAS , J., concurring in judgment). Thus, even assum

ing the existence of some tension between Arizona’s law and the supposed “purposes and objectives” of Congress, I would not hold that any of the provisions of the Arizona law at issue here are pre-empted on that basis._________________

_________________ 1 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.



## SUPREME COURT OF THE UNITED STATES

No. 11–182

ARIZONA, ET AL ., PETITIONERS v. UNITED STATES

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF

APPEALS FOR THE NINTH CIRCUIT

[June 25, 2012]

J USTICE A LITO , concurring in part and dissenting in
part.
This case concerns four provisions of Arizona’s Support Our Law Enforcement and Safe Neighborhoods Act, S. B. 1070. Section 2(B) requires Arizona law enforcement
officers to make a “reasonabl e attempt,” “when practica

ble,” to ascertain the immigration status of any person whom an officer lawfully stops, detains, or arrests “where

reasonable suspicion exists that the person is an alien and is unlawfully present in the United States.” Ariz. Rev. Stat. Ann. §11–1051(B) (West 2012). Section 3 provides that an alien who willfully fails “to complete or carry an alien registration document” in violation of 8 U. S. C. §1304(e) or §1306(a) is guilty of a misdemeanor. Ariz. Rev. Stat. Ann. §13–1509(A) (West Supp. 2011). Section 5(C)
makes it a misdemeanor for an unauthorized alien who is unlawfully present in the United States “to knowingly apply for work, solicit work in a public place or perform work as an employee or independent contractor.” Ariz. Rev. Stat. Ann. §13–2928(C). And §6 authorizes Arizona
law enforcement officers to arrest without a warrant any person who an officer has probable cause to believe “has committed any public offense that makes the person re

movable from the United States.” Ariz. Rev. Stat. Ann. §13–3883(A)(5). I agree with the Court that §2(B) is not pre-empted.2 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

That provision does not autho rize or require Arizona law
enforcement officers to do anything they are not already allowed to do under existing federal law. The United States’ argument that §2(B) is pre-empted, not by any federal statute or regulation, but simply by the Executive’s current enforcement policy is an astounding assertion of federal executive power that the Court rightly rejects. I also agree with the Court that §3 is pre-empted by
virtue of our decision in Hines v. Davidowitz , 312 U. S. 52 (1941). Our conclusion in that case that Congress had enacted an “all-embracing system” of alien registration and that States cannot “enforce additional or auxiliary regulations,” id., at 66–67, 74, forecloses Arizona’s attempt here to impose additional, state-law penalties for viola

tions of the federal registration scheme. While I agree with the Court on §2(B) and §3, I part ways on §5(C) and §6. The Court’s holding on §5(C) is

inconsistent with De Canas v. Bica , 424 U. S. 351 (1976), which held that employment regulation, even of aliens unlawfully present in the country, is an area of traditional

state concern. Because state police powers are implicated here, our precedents require us to presume that federal law does not displace state law unless Congress’ intent to do so is clear and manifest. I do not believe Congress has spoken with the requisite clarity to justify invalidation of §5(C). Nor do I believe that §6 is invalid. Like §2(B), §6 adds virtually nothing to the authority that Arizona law enforcement officers already ex ercise. And whatever little authority they have gained is consistent with federal law.

Section 2(B)

A
Although §2(B) of the Arizona law has occasioned much controversy, it adds nothing to the authority that Arizona law enforcement officers, like o fficers in all other States, already possess under federal law. For that reason, I3 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

agree with the Court that §2(B) is not pre-empted. Section 2(B) quite clearly does not expand the authority of Arizona officers to make stops or arrests. It is triggered only when a “lawful stop, detention or arrest [is] made . . .
in the enforcement of any other [state or local] law or
ordinance .” Ariz. Rev. Stat. Ann. §11–1051(B) (emphasis added). Section 2(B) thus comes into play only when an officer has reasonable suspicion or probable cause to believe that a person has committed a nonimmigration offense. Arizona officers pl ainly possessed this authority before §2(B) took effect. Section 2(B) also does not expand the authority of Ari

zona officers to inquire about the immigration status of persons who are lawfully detained. When a person is stopped or arrested and “reasonable suspicion exists that the person is an alien and is unlawfully present in the United States,” §2(B) instructs Arizona officers to make a “reasonable attempt,” “when practicable,” to ascertain that person’s immigration status. Ariz. Rev. Stat. Ann. §11– 1051(B). Even before the Ar izona Legislature enacted §2(B), federal law permitted state and local officers to make such inquiries. In 8 U. S. C. §1357(g)(10)(A), Con

gress has made clear that state and local governments need not enter into formal agreements with the Federal Government in order “to communicate with the [Federal Government] regarding the immigration status of any individual.” In addition, Congress has mandated that neither the Federal Government nor any state or local government may “prohibit, or in any way restrict, any government entity or official from sending to, or receiving from, [the Federal Government ] information regarding the citizenship or immigration status, lawful or unlawful, of any individual.” §1373(a); see also §1644 (providing that “no State or local government entity may be prohibited, or in any way restricted, from sending to or receiving from [the Federal Government ] information regarding the4 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

immigration status, lawful or unlawful, of an alien in the United States”). And while these provisions preserve the authority of state and local officers to seek immigration

status information from the Federal Government, another federal statute, §1373(c), requires that the Federal Gov

ernment respond to any such inquiries “by providing the requested verification or stat us information.” It comes as no surprise, therefore, that many States and localities permit their law enforcement o fficers to make the kinds of inquiries that §2(B) prescribes. See App. 294–298 (report

ing that officers in 59 surveyed state and local jurisdic

tions “generally” ask arrestees about their immigration status while 34 do not and that officers in 78 jurisdictions “generally” inform Immigration and Customs Enforcement (ICE) when they believe an arrestee to be an undocumented alien while only 17 do not). Congress has invited state and local governments to make immigration-related in

quiries and has even obligated the Federal Government to respond. Through §2(B), Arizona has taken Congress up

on that invitation. The United States does not deny that officers may, at
their own discretion , inquire about the immigration status of persons whom they lawfully detain. Instead, the United States argues that §2(B) is pre-empted because it impedes federal-state cooperation by mandating that officers verify the immigration status of every detained person if there is reason to believe that the person is unlawfully present in the country. The United States claims that §2(B)’s man

date runs contrary to federal law in that it “precludes officers from taking [the Fe deral Government’s] priorities
and discretion into account.” Brief for United States

50. “[B]y interposing a mandatory state law between state and local officers and their federal counterparts,” writesthe United States, §2(B) “stands as an obstacle to the accomplishment of the federal requirement of cooperation and the full effectuation of the enforcement judgment and5 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

discretion Congress has vested in the Executive Branch.”

Ibid. (internal quotation marks and citation omitted). The underlying premise of the United States’ argument seems to be that state and local officers, when left to their own devices, generally take fe deral enforcement priorities

into account. But there is no reason to think that this premise is true. And even if it were, it would not follow that §2(B)’s blanket mandate is at odds with federal law. Nothing in the relevant federal statutes requires state and
local officers to consider th e Federal Government’s priori

ties before requesting verifica tion of a person’s immigra

tion status. Neither 8 U. S. C. §1357(g)(10) nor §1373(a) conditions the right of state and local officers to communi

cate with the Federal Govern ment on their first taking account of its priorities. Nor does §1373(c) condition the Federal Government’s obligatio n to answer requests for information on the sensitivity of state and local officers to
its enforcement discretion. In fact, §1373(c) dictates that
the Federal Government “sha ll respond” to any inquiry seeking verification of immigration status, and that com

mand applies whether or not the requesting officer has bothered to consider federal priorities. Because no federal statute requires such considerat ion, §2(B) does not conflict
with federal law.In any event, it is hard to see how state and local officers could proceed in conformi ty with the Federal Govern

ment’s enforcement priorities without making an inquiry into a suspected alien’s immigration status. For example,
one of the Federal Government’s highest priorities is the apprehension and removal of aliens who have failed to comply with a final order of removal. See App. 108. How can an officer identify those persons without first in

quiring about their status? At bottom, the discretion that ultimately matters is not whether to verify a person’s immigration status but whether to act once the person’s status is known. For that reason, §2(B)’s verification6 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

requirement is not contrary to federal law because the
Federal Government retains the discretion that matters most––that is, the discretion to enforce the law in par

ticular cases. If an Arizona officer contacts the Federal Government to verify a person’s immigration status and federal records reveal that the person is in the coun

try unlawfully, the Federal Go vernment decides, presum

ably based on its enforcement priorities, whether to have the person released or transferred to federal custody.
Enforcement discretion thus lies with the Federal Gov

ernment, not with Arizona. Nothing in §2(B) suggests

otherwise. The United States’ attack on §2(B) is quite remarkable. The United States suggests that a state law may be pre

empted, not because it conflicts with a federal statute or regulation, but because it is inconsistent with a federal agency’s current enforcement priorities. Those priorities, however, are not law. They are nothing more than agency policy. I am aware of no decision of this Court recognizing that mere policy can have pre-emptive force. Cf. Barclays
Bank PLC v. Franchise Tax Bd. of Cal. , 512 U. S. 298, 330 (1994) (holding that “Executive Branch communications that express federal policy but lack the force of law cannot render unconstitutional” an “otherwise valid, congression

ally condoned” state law). If §2(B) were pre-empted at the present time because it is out of sync with the Federal Government’s current prioriti es, would it be unpre-empted
at some time in the future if the agency’s priorities changed? Like most law enforcement agencies, ICE does not set
out inflexible rules for its offi cers to follow. To the con

trary, it provides a list of factors to guide its officers’
enforcement discretion on a ca se-by-case basis. See Memo

randum from John Morton, Director, ICE, to All Field Office Directors et al., p. 4 ( June 17, 2011) (“This list is not
exhaustive and no one factor is determinative. ICE offi

-7 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

cers, agents, and attorneys sh ould always consider prose

cutorial discretion on a case-by-case basis. The decisions should be based on the totality of the circumstances, with the goal of conforming to ICE’s enforcement priorities”). Among those factors is “the agency’s civil immigration enforcement priorities,” ibid. , which change from admin

istration to administration. If accepted, the United States’ pre-emption argument would give the Executive unprece

dented power to invalidate state laws that do not meet with its approval, even if the state laws are otherwise consistent with federal statutes and duly promulgated regulations. This argument, to say the least, is fundamen

tally at odds with our federal system.

B
It has been suggested that §2(B) will cause some per

sons who are lawfully stopped to be detained in violation of their constitutional rights while a prolonged investiga

tion of their immigration status is undertaken. But noth

ing on the face of the law suggests that it will be enforced in a way that violates the Fourth Amendment or any other provision of the Constitution. The law instructs officers to make a “reasonable attempt” to investigate immigration status, and this language is best understood as incorporat

ing the Fourth Amendment’s standard of reasonableness. Indeed, the Arizona Legislature has directed that §2(B) “shall be implemented in a manner consistent with federal laws . . . protecting the civil rights of all persons and re

specting the privileges and immunities of United States citizens.” Ariz. Rev. Stat. Ann. §11–1051(L). In the situations that seem most likely to occur, en

forcement of §2(B) will present familiar Fourth Amend

ment questions. To take a common situation, suppose that a car is stopped for speeding, a nonimmigration offense. (Recall that §2(B) comes into play only where a stop or arrest is made for a nonimmigration offense.) Suppose8 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

also that the officer who makes the stop subsequently acquires reasonable suspicion to believe that the driver entered the country illegally, which is a federal crime. See 8 U. S. C. §1325(a). It is well established that state and local officers gener

ally have authority to make stops and arrests for viola

tions of federal criminal laws. See, e.g., Miller v. United
States , 357 U. S. 301, 305 (1958); United States v. Di Re

, 332 U. S. 581, 589 (1948). I see no reason why this princi

ple should not apply to immigration crimes as well. Lower courts have so held. See, e.g., Estrada v. Rhode Island

, 594 F. 3d 56, 65 (CA1 2010) (upholding the lawfulness ofa detention because the officer had an objectively reasonable belief that the arrestees “had committed immigra

tion violations”); United States v. Vasquez-Alvarez , 176
F. 3d 1294, 1296 (CA10 1999) (noting that “state law

enforcement officers have the general authority to investi

gate and make arrests for vi olations of federal immigra

tion laws”); Gonzales v. Peoria , 722 F. 2d 468, 475 (CA9 1983), overruled on other grounds, Hodgers-Durgin v. de

la Vina , 199 F. 3d 1037 (1999) (en banc) (holding that “federal law does not preclude local enforcement of the criminal provisions” of federal immigration law). And the United States, consistent with the position long taken by the Office of Legal Counsel (OLC) in the Department of Justice, does not contend otherwise. See Brief for United States 55, n. 33; see also Memorandum from OLC to the Attorney General (Apr. 3, 2002), App. 268–273; Assistance by State and Local Police in Apprehending Illegal Aliens, 20 Op. Off. Legal Counsel 26 (1996). More importantly, no federal statute casts doubt on this authority. To be sure, there are a handful of statutes that purport to authorize state and local officers to make immi

gration-related arrests in certain situations. See, e.g., 8
U. S. C. §1103(a)(10) (providing for the extension of “any” immigration enforcement authority to state and local9 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

officers in the event of an “actual or imminent mass influx of aliens arriving off the coast”); §1252c(a) (providing authority to arrest criminal aliens who had illegally reentered the country but only after consultation with the Federal Government); § 1324(c) (providing authority to make arrests for transpo rting and harboring certain aliens). But a grant of federal arrest authority in some cases does not manifest a clear congressional intent to displace the States’ police powers in all other cases. With

out more, such an inference is too weak to overcome our presumption against pre-emption where traditional state police powers are at stake. Accordingly, in our hypothet

ical case, the Arizona officer may arrest the driver for violating §1325(a) if the officer has probable cause. And if the officer has reasonable susp icion, the officer may detain the driver, to the extent permitted by the Fourth Amend

ment, while the question of ill egal entry is investigated.

We have held that a detention based on reasonable suspicion that the detainee committed a particular crime “can become unlawful if it is prolonged beyond the time reasonably required to complete that mission.” Illinois v. Caballes , 543 U. S. 405, 407 (2005). But if during the course of a stop an officer acquires suspicion that a detainee committed a different crime, the detention may be
extended for a reasonable time to verify or dispel that suspicion. Cf. Muehler v. Mena , 544 U. S. 93, 101 (2005) (holding that “no additional Fourth Amendment justifica

tion” was required because any questioning concerning immigration status did not prolong the detention). In our hypothetical case, therefore, if the officer, after initially stopping the car for speeding, has a reasonable suspicion that the driver entered the country illegally, the officer may investigate for evidence of illegal entry. But the length and nature of this investigation must remain with

in the limits set out in our Fourth Amendment cases. An investigative stop, if prolonged, can become an arrest and10 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

thus require probable cause. See Caballes

, supra , at 407. Similarly, if a person is moved from the site of the stop, probable cause will likely be required. See Hayes v. Florida

, 470 U. S. 811, 816 (1985) (holding that the line be

tween detention and arrest is crossed “when the police, without probable cause or a warrant, forcibly remove a person from his home or other place in which he is entitled to be and transport him to the police station, where he is detained, although briefly, for investigative purposes”). If properly implemented, §2(B) should not lead to fed

eral constitutional violations, but there is no denying that enforcement of §2(B) will multiply the occasions on which sensitive Fourth Amendment issues will crop up. These civil-liberty concerns, I take it, are at the heart of mostobjections to §2(B). Close and difficult questions will inevitably arise as to whether an officer had reasonable suspicion to believe that a person who is stopped for some other reason entered the country illegally, and there is a risk that citizens, lawful permanent residents, and others who are lawfully present in the country will be detained. To mitigate this risk, Arizona could issue guidance to officers detailing the circumst ances that typically give rise to reasonable suspicion of unlawful presence. And in the spirit of the federal-stat e cooperation that the United States champions, the Federa l Government could share its own guidelines. Arizona could also provide officers with a nonexclusive list containing forms of identification suffi

cient under §2(B) to dispel any suspicion of unlawful presence. If Arizona accepts licenses from most States as proof of legal status, the problem of roadside detentions will be greatly mitigated. 1

——————

1 When the Real ID Act takes effect , the Federal Government will no longer accept state forms of identi fication that fail to meet certain federal requirements. §202(a)(1), 119 Stat. 312. One requirement is that any identification be issued only on proof that the applicant is lawfully present in the United States. §202(c)(2)(B), id., at 313. I11 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

Section 3 I agree that §3 is pre-empted because, like the Court, I read the opinion in Hines to require that result. Although there is some ambiguity in Hines , the Court largely spoke in the language of field pre-emption. The Court explained that where Congress “has enacted a complete scheme of regulation and has therein provided a standard for the registration of aliens, states cannot, inconsistently with the purpose of Congress, conflict or interfere with, curtail or complement, the federal law, or enforce additional or auxiliary regulations.” 312 U. S., at 66–67. In finding the Pennsylvania alien-registration law pre-empted, the Court observed that Congress had “provided a standard for alien registration in a single integrated and all-embracing system” and that its intent was “to protect the personal liberties of law-abiding aliens through one uniform na

tional registration system.” Id., at 74. If we credit our holding in Hines that Congress has enacted “a single integrated and all-embracing system” of alien registration and that States cannot “comple ment” that system or “en

force additional or auxiliary regulations,” id., at 66–67, 74, then Arizona’s attempt to impose additional, state-law penalties for violations of federal registration require

ments must be invalidated.

Section 5(C)
While I agree that §3 is pre-empted, I disagree with the Court’s decision to strike down §5(C). I do so in large measure because the Court fails to give the same solici

tude to our decision in De Canas , 424 U. S. 351, as it is willing to give our decision in Hines . In De Canas , the Court upheld against a pre-emption challenge a state law imposing fines on employers that hired aliens who were

—————— anticipate that most, if not all, St ates will eventually issue forms of
identification that suffice to esta blish lawful presence under §2(B).12 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

unlawfully present in the United States. The Court ex

plained that the mere fact that “aliens are the subject of a state statute does not render it a regulation of immigra

tion.” 424 U. S., at 355. The Court emphasized instead that “States possess broad authority under their police powers to regulate the employment relationship to protect
workers within the State.” Id., at 356. In light of that broad authority, the Court decl ared that “[o]nly a demon

stration that complete ouster of state power . . . was ‘the clear and manifest purpose of Congress’ would justify” the conclusion that “state regulation designed to protect vital state interests must give way to paramount federal legis

lation.” Id., at 357 (some internal quotation marks omit

ted); see also Bates v. Dow Agrosciences LLC , 544 U. S. 431, 449 (2005) (“In areas of traditional state regulation, [the Court] assume[s] that a federal statute has not sup

planted state law unless Congress has made such an
intention ‘clear and manifest’ ” (some internal quotation marks omitted)). The Court now tells us that times have changed. Since
De Canas , Congress has enacted “a comprehensive frame

work for combating the employme nt of illegal aliens,” and even though aliens who seek or obtain unauthorized work are not subject to criminal sanctions, they can suffer civil penalties. Ante, at 12–13 (internal quotation marks omit

ted). Undoubtedly, federal regulation in this area is more pervasive today. But our task remains unchanged:
to determine whether the federal scheme discloses a clear and manifest congressional intent to displace state law. The Court gives short shrift to our presumption against pre-emption. Having no express statement of congres

sional intent to support its analysis, the Court infers from stale legislative history and from the comprehensiveness
of the federal scheme that “Congress made a deliberate choice not to impose criminal penalties on aliens who seek, or engage in, unauthorized employment.” Ante, at 13.13 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

Because §5(C) imposes such penalties, the Court concludes

that it stands as an obstacle to the method of enforcement chosen by Congress. Ante, at 15. The one thing that is clear from the federal scheme is that Congress chose not to impose federal criminal penal

ties on aliens who seek or obtain unauthorized work. But that does not mean that Congress also chose to pre-empt

state criminal penalties. The inference is plausible, but far from necessary. As we have said before, the “decision not to adopt a regulation” is not “the functional equivalent of a regulation prohibiting all States and their political subdivisions from adopting such a regulation.” Sprietsma

v. Mercury Marine , 537 U. S. 51, 65 (2002). With any statutory scheme, Congress chooses to do some things and not others. If that alone were enough to demonstrate pre

emptive intent, there would be little left over for the States to regulate, especially now that federal authority
reaches so far and wide. Stat es would occupy tiny islands in a sea of federal power. This explains why state laws implicating traditional state powers are not pre-empted unless there is a “clear and manifest” congressional inten

tion to do so. Not only is there little evidence that Congress intended to pre-empt state laws like §5(C), there is some evidence that Congress intended the opposite result. In making it unlawful for employers to hire unauthorized aliens, see 8

U. S. C. §1324a(a), Congress made it clear that “any State or local law imposing civil or criminal sanctions (other than through licensing and similar laws)” upon employers was pre-empted, §1324a(h)(2). Noticeably absent is any similar directive pre-empting state or local laws targeting aliens who seek or obtain unauthorized employment. Given that Congress expressl y pre-empted certain state and local laws pertaining to employers but remained silent about laws pertaining to employees, one could infer that Congress intended to preserve state and local authority to14 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

regulate the employee side of the equation. At the very least, it raises serious doubts about whether Congress intended to pre-empt such authority. The Court dismisses any inferences that might be drawn from the express pre-emption provision. See ante, at 14. But even though the existence of that provision
“does not bar the ordinary working of conflict pre-emption principles” or impose a “ ‘special burden’ ” against pre

emption, Geier v. American Honda Motor Co. , 529 U. S. 861, 869–870 (2000), it is still probative of congressional intent. And it is the intent of Congress that is the “ulti

mate touchstone.” Retail Clerks v. Schermerhorn , 375
U. S. 96, 103 (1963). The Court infers from Congre ss’ decision not to impose federal criminal penalties that Congress intended to pre

empt state criminal penalties. But given that the express pre-emption provision covers only state and local laws regulating employers , one could just as well infer that Congress did not intend to pr e-empt state or local laws

aimed at alien employees who unlawfully seek or obtain work. Surely Congress’ decisi on not to extend its express pre-emption provision to state or local laws like §5(C) is more probative of its intent on the subject of pre-emption than its decision not to impose federal criminal penalties for unauthorized work. In any event, the point I wish to emphasize is that inferences can be drawn either way. There are no necessary inferences that point decisively for or against pre-emption. Therefore, if we take seriously that state employment regulation is a traditional state concern and can be pre-empted only on a showing of “clear and manifest” congressional intent as required by De
Canas , then §5(C) must survive. “Our precedents estab

lish that a high threshold must be met if a state law is to be pre-empted for conflicting with the purposes of a fed

eral Act.” Chamber of Commerce of United States of America

v. Whiting , 563 U. S. ___, ___ (2011) (plurality opinion)15 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

(slip op., at 22) (internal quotation marks omitted). I do
not believe the United States has surmounted that barrier

here.

Section 6
I also disagree with the Court’s decision that §6 is pre

empted. This provision adds little to the authority that Arizona officers already posse ss, and whatever additional authority it confers is consiste nt with federal law. Section
6 amended an Arizona statute that authorizes warrantless arrests. See Ariz. Rev. Stat. §13–3883 (West 2010). Be

fore §6 was added, that stat ute already permitted arrests
without a warrant for feloni es, misdemeanors committed in the arresting officer’s presence, petty offenses, and certain traffic-related criminal violations. See §§13– 3883(A)(1)–(4). Largely duplicating the authority already conferred by these prior subsections, §6 added a new subsection, §13–3883(A)(5) (West Supp. 2011), that au

thorizes officers to make warrantless arrests on probable cause that the arrestee has committed a “public offense”
for which the arrestee is removable from the United States. A “public offense” is defined as conduct that is punishable by imprisonment or a fine according to the law
of the State where the conduct occurred and that would be punishable under Arizona law had the conduct occurred in Arizona. See §13–105(27). In what way, if any, does §6 enlarge the arrest authority of Arizona officers? It has been suggested that §6 confers new authority in the following three circumstances: (1) where the arrestee committed but has not been charged with committing an offense in another State; (2) where the officer has probable cause to believe the arrestee commit

ted an offense for which he was previously arrested but not prosecuted; and (3) where the arrestee committed but has already served the sentence for a removable offense. 641 F. 3d 359, 361 (CA9 2011). These are exceedingly16 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

narrow categories, in volving circum stances that will rarely arise. But such cases are possible, and therefore we must
decide whether there are circumstances under which fed

eral law precludes a state officer from making an arrest based on probable cause that the arrestee committed a
removable offense.

A
The idea that state and local officers may carry out arrests in the service of federal law is not unprecedented. As previously noted, our cases establish that state and local officers may make warrantless arrests for violations of federal law and that “in the absence of an applicable
federal statute the law of the state where an arrest with

out warrant takes place determines its validity.” Di Re

, 332 U. S., at 589; see also Miller, 357 U. S., at 305 (stating that, where a state officer makes an arrest based on fed

eral law, “the lawfulness of the arrest without warrant is to be determined by reference to state law”). Therefore, given the premise, which I understand both the United States and the Court to accept, that state and local officersdo have inherent authority to make arrests in aid of federal law, we must ask whether Congress has done anything to curtail or pre-empt that authority in this particular

case. Neither the United States nor the Court goes so far as to say that state and local office rs have no power to arrest criminal aliens based on their removability. To do so would fly in the face of 8 U. S. C. §1357(g)(10). Under §§1357(g)(1)–(9), the Federal Government may enter into formal agreements with States and municipalities underwhich their officers may perform certain duties of a federal immigration officer. But §1357(g)(10)(B) makes clear that States and municipalities need not enter into those agreements “otherwise to cooperate . . . in the identifica

tion, apprehension, detention, or removal of aliens not17 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

lawfully present in the United States.” It goes without saying that state and local officers could not provide meaningful cooperation in the apprehension, detention,
and ultimate removal of criminal aliens without some power to make arrests. Although §1357(g)(10) contemplates state and local authority to apprehend criminal aliens for the purpose of removal, the Court rejects out of hand any possibility that officers could exercise that authority without federal direction. Despite acknowledgin g that there is “ambiguity as to what constitutes cooperation,” the Court says that “no coherent understanding of the term would incorporate
the unilateral decision of stat e officers to arrest an alien for being removable absent any request, approval, or other
instruction from the Federal Government.” Ante, at 18. The Court adopts an unnecessarily stunted view of coop

eration. No one would say that a state or local officer has failed to cooperate by making an on-the-spot arrest to enforce federal law. Unsolicited aid is not necessarily uncooperative. To be sure, were an officer to persist in making an ar

rest that the officer knows is unwanted, such conduct would not count as cooperation. But nothing in the rele

vant federal statutes sugge sts that Congress does not
want aliens who have committed removable offenses to be

arrested. 2 To the contrary, §1226(c)(1) commands that the Executive “shall take into custody any alien” who is de

portable for having committed a specified offense. And §1226(c)(2) substantially limits the circumstances under

which the Executive has discretion to release aliens held in custody under paragraph (1). So if an officer arrests an alien who is removable for having committed one of the crimes listed in §1226(c)(1), the Federal Government is

——————

2 That goes for the Executive Bran ch as well, which has made the apprehension and removal of criminal aliens a priority. See App. 108.18 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

obligated to take the alien into custody. That Congress generally requires the Executive to take custody of criminal aliens casts considerable doubt on the Court’s concern that §6 is an obstacle to the Federal Gov

ernment’s exercise of discretion. The Court claims that the authority conferred by §6 “could be exercised without any input from the Federal Government about whether an arrest is warranted in a particular case” and that this
“would allow the State to achieve its own immigration policy,” resulting in the “unnecessary harassment of some
aliens . . . whom federal officials determine should not be
removed.” Ante, at 17. But §1226(c)(1) belies the Court’s fear. In many, if not most, cases involving aliens who are removable for having committed criminal offenses, Con

gress has left the Executive no discretion but to take thealien into custody. State and local officers do not frustrate the removal process by arresting criminal aliens. The Executive retains complete discretion over whetherthose aliens are ultimately removed. And once the Federal Government makes a determination that a particular

criminal alien will not be remo ved, then Arizona officers are presumably no longer authorized under §6 to arrest

the alien. To be sure, not all offenses for which officers have au

thority to arrest under §6 are covered by §1226(c)(1). As for aliens who have committed those offenses, Congress has given the Executive discretion under §1226(a) over

whether to arrest and detain them pending a decision on
removal. But the mere fact that the Executive has en

forcement discretion cannot mean that the exercise of state police powers in support of federal law is automati

cally pre-empted. If that were true, then state and local
officers could never make a rrests to enforce any federal statute because the Executive always has at least some general discretion over the enforcement of federal law as a practical matter. But even assuming that the express19 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

statutory grant of discretion in §1226(a) somehow indi

cates a congressional desire to pre-empt unilateral state and local authority to arrest criminal aliens covered by that provision, §6 is not pre- empted on its face given its substantial overlap with §1226(c)(1). It bears emphasizing that §6 does not mandate the warrantless apprehension of all aliens who have commit

ted crimes for which they are removable. Instead, it only grants state and local officers permission to make such arrests. The trouble with this premature, facial challenge is that it affords Arizona no opportunity to implement its law in a way that would avoid any potential conflicts with federal law. For exampl e, Arizona could promulgate guidelines or regulations limiting the arrest authority conferred by §6 to the crimes specified in §1226(c)(1). And to the extent §1226(c)(1) is unclear about which exact crimes are covered, 3 Arizona could go even further and identify specific crimes for which there is no doubt an alien would be removable. The point is that there are plenty of permissible applications of §6, and the Court should not invalidate the statute at this point without at least some indication that Arizona has implemented it in a manner at odds with Congress’ clear and manifest intent.
We have said that a facial c hallenge to a statute is “the most difficult challenge to mount successfully” because “the challenger must establish that no set of circumstances exists under which the [statute] would be valid.” United
States v. Salerno , 481 U. S. 739, 745 (1987); see also

Anderson v. Edwards , 514 U. S. 143, 155, n. 6 (1995) (applying the Salerno standard in a pre-emption case). As to §6, I do not believe the United States has carried that

——————

3 I readily admit that it can be difficult to determine whether a particular conviction w ill necessarily make an alien removable. See

Padilla v. Kentucky , 559 U. S. ___, ___ (2010) (A LITO

, J., concurring in judgment) (slip op., at 4).20 ARIZONA v. UNITED STATES

Opinion of A LITO

, J.

heavy burden.

B
Finally, the Court tells us that §6 conflicts with federal law because it provides state and local officers with “even greater authority to arrest aliens on the basis of possible removability than Congress has given to trained federal immigration officers.” Ante, at 16–17. The Court points to8 U. S. C. §1357(a)(2), which empowers “authorized” officers and employees of ICE to make arrests without a federal warrant if “the alien so arrested is in the United States in violation of any [immigration] law or regulation and is likely to escape before a warrant can be obtained for his arrest.” Because §6 would a llow Arizona officers to make arrests “regardless of whether a federal warrant has issued or the alien is likely to escape,” ante, at 17, the Court concludes that §6 is an obstacle to the accomplish

ment of Congress’ objectives. But §6 is an obstacle only to
the extent it conflicts with Congress’ clear and manifest intent to preclude state and local officers from making arrests except where a federal warrant has issued or the arrestee is likely to escape. By granting warrantless arrest authority to federal officers , Congress has not mani

fested an unmistakable intent to strip state and local officers of their warrantless arrest authority under state

law. Likewise, limitations on federal arrest authority do not mean that the arrest authority of state and local officers must be similarly limited. Our opinion in Miller, 357 U. S. 301, is instructive. In that case, a District of Columbia officer, accompanied by a fede ral officer, made an arrest based on a suspected federal narcotics offense. Id., at 303–304. The federal officer did not have statutory au

thorization to arrest without a warrant, but the local
officer did. Id., at 305. We held that District of Columbia
law dictated the lawfulness of the arrest. Id., at 305–306.21 Cite as: 567 U. S. ____ (2012)

Opinion of A LITO

, J.

Where a state or local officer makes a warrantless arrest to enforce federal law, we said that “the lawfulness of the

arrest without warrant is to be determined by reference to
state law.” Id., at 305. Under §6, an Arizona officer may

be authorized to make an arrest that a federal officer may not be authorized to make under §1357(a)(2). As Miller makes clear, that fact alone does not render arrests by state or local officers pursuant to §6 unlawful. Nor does it manifest a clear congressional intent to displace the exer

cise of state police powers that are brought to bear in aid
of federal law.