In Arizona v. United States, 567 U.S. 387 (2012), the Supreme Court struck down three of the four challenged provisions of Arizona’s SB 1070 and let a fourth stand for the time being. By a 5–3 vote, the Court held that federal immigration law preempts state efforts to create parallel criminal penalties, expand arrest authority, or otherwise build a separate enforcement system alongside the one Congress designed. Only Section 2(B), the status-check requirement often called the “show me your papers” provision, survived the facial challenge, and even it survived only because the Court said it was too early to know how enforcement would play out.
What the Court Struck Down
Three provisions of SB 1070 fell. Each one tried to give Arizona its own enforcement tool in an area Congress had already regulated, and in each instance the Court found that the state law disrupted the federal scheme.
Section 3: State Penalties for Federal Registration Violations
Section 3 made it a state misdemeanor for a noncitizen to fail to carry a valid federal registration document.1Justia. Arizona v. United States, 567 U.S. 387 (2012) Federal law already required noncitizens eighteen and older to carry that card, with fines up to $100 or up to 30 days in jail for failing to do so,2Office of the Law Revision Counsel. 8 USC 1304 – Forms for Registration and Fingerprinting and stiffer penalties, up to $1,000 and six months, for willful failure to register at all.3Office of the Law Revision Counsel. 8 USC 1306 – Penalties
The Court held that Congress had occupied the entire field of alien registration. It leaned on Hines v. Davidowitz (1941), which had described the federal registration framework as a “comprehensive and integrated scheme” leaving no room for state supplementation.4Justia U.S. Supreme Court Center. Hines v. Davidowitz, 312 U.S. 52 (1941) Even a state law that merely duplicated a federal registration rule was impermissible, because it would let state prosecutors bring charges in situations where federal officials might deliberately choose restraint.5Legal Information Institute. Arizona v. United States
Section 5(C): Criminalizing Unauthorized Work
Section 5(C) made it a class 1 misdemeanor for an unauthorized noncitizen to apply for work, solicit work in a public place, or perform work in Arizona.6Arizona Legislature. SB 1070 Under Arizona law, that carries up to six months in jail.7Arizona Legislature. Arizona Revised Statutes 13-707 – Misdemeanors Sentencing
The Court struck this provision down under conflict preemption. When Congress passed the Immigration Reform and Control Act of 1986, it imposed civil and criminal penalties on employers who hired unauthorized workers but deliberately declined to criminalize the workers themselves. The majority wrote that “Congress decided it would be inappropriate to impose criminal penalties on aliens who seek or engage in unauthorized employment,” and that Arizona’s contrary choice was “an obstacle to the regulatory system Congress chose.”5Legal Information Institute. Arizona v. United States Unauthorized employment can carry immigration consequences like removal, but Congress had reserved that response to the civil immigration system.
Section 6: Warrantless Arrests for Suspected Removable Noncitizens
Section 6 authorized state and local police to make warrantless arrests whenever an officer had probable cause to believe a person was a noncitizen who had committed an offense making them removable, or who had previously been deported.8Arizona Legislature. SB 1070 Federal law is far more restrictive: even trained immigration officers can only make warrantless arrests for immigration violations when the person “is likely to escape before a warrant can be obtained.”9Office of the Law Revision Counsel. 8 USC 1357 – Powers of Immigration Officers and Employees
Removability is a civil determination, and the Court emphasized that the decision to pursue removal involves foreign relations, humanitarian concerns, and enforcement priorities. Those decisions, the majority wrote, “must be made with one voice.”5Legal Information Institute. Arizona v. United States Federal law does allow state officers to help identify and apprehend removable noncitizens, but only through formal 287(g) agreements under 8 U.S.C. § 1357(g), where officers receive federal training and act under federal supervision.9Office of the Law Revision Counsel. 8 USC 1357 – Powers of Immigration Officers and Employees Section 6 bypassed that structure. The Court called it “not the system Congress created.”
What Survived: Section 2(B)
Section 2(B) required officers to make a reasonable attempt to check the immigration status of anyone they lawfully stopped, detained, or arrested if the officer had reasonable suspicion the person lacked authorization to be in the country.1Justia. Arizona v. United States, 567 U.S. 387 (2012) Verification runs through the Law Enforcement Support Center, an ICE-operated service that provides around-the-clock immigration status information to law enforcement.10U.S. Immigration and Customs Enforcement. Law Enforcement Support Center
The majority allowed this provision to stand, but the ruling was narrow. The Court did not declare Section 2(B) constitutional in all applications. It held only that a facial challenge before Arizona’s state courts had interpreted the provision was premature. Federal law already contemplates information sharing between state and federal officers on immigration status, so formalizing that communication did not automatically conflict with the federal scheme. If Section 2(B) only required checks during otherwise-lawful detentions, the Court said, “the provision would likely survive preemption.”5Legal Information Institute. Arizona v. United States
The opinion openly flagged how the provision could still fail. A status check that prolonged a stop beyond what the original reason justified could violate the Fourth Amendment. An enforcement pattern producing racial profiling or civil rights violations would invite new suits. The Court expressly said its opinion “does not foreclose other preemption and constitutional challenges to the law as interpreted and applied.”5Legal Information Institute. Arizona v. United States
Those follow-on challenges arrived. In 2016, Arizona’s Attorney General issued an opinion setting constitutional limits on enforcement: officers could not use race or ethnicity to develop reasonable suspicion of unlawful presence, could not stop people solely to investigate immigration status, and could not extend a stop beyond the time needed for its original purpose just to run a status check. Those constraints narrowed the practical reach of the provision considerably.
The Preemption Reasoning
The whole case ran on the Supremacy Clause of Article VI, which makes federal law override conflicting state law.11Congress.gov. U.S. Constitution – Article VI The Court used two flavors of preemption to reach its results.
Field preemption applies when Congress has regulated so thoroughly that no room remains for states to add their own rules. That was the ground for striking Section 3, following Hines.
Conflict preemption applies more broadly. Even without full federal occupation of a field, a state law fails if it “stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress.”5Legal Information Institute. Arizona v. United States That standard defeated Sections 5(C) and 6. The point of both rulings is that Congress’s chosen approach, including the choices Congress made not to criminalize certain conduct or not to authorize certain arrests, carries preemptive weight. A state cannot rewrite those choices by adding its own penalties or powers.
The Dissents
Justice Kennedy wrote for a majority that included Chief Justice Roberts and Justices Ginsburg, Breyer, and Sotomayor. Justice Kagan was recused. Three justices dissented in part.
Justice Scalia argued that Arizona was exercising a sovereign power older than the Constitution itself: the power of a state to exclude people from its territory. He pointed to early American practice, including state laws restricting entry of convicted criminals and people carrying contagious diseases, and asked whether “the sovereign States [are] at the mercy of the Federal Executive’s refusal to enforce the Nation’s immigration laws.”5Legal Information Institute. Arizona v. United States He would have upheld all four provisions.
Justice Thomas took a textualist route to the same result. He argued that preemption should turn on whether the “ordinary meanings” of federal and state law actually conflict, not on inferences about congressional purpose. He read IRCA’s silence on employee penalties as leaving states free to act, not as a deliberate policy choice.5Legal Information Institute. Arizona v. United States
Justice Alito agreed with the majority on Sections 2(B) and 3 but dissented on Sections 5(C) and 6. On employment, he invoked De Canas v. Bica (1976), which treated employment regulation as an area of traditional state concern and required a “clear and manifest purpose of Congress” to displace state power.12Justia U.S. Supreme Court Center. De Canas v. Bica, 424 U.S. 351 (1976) Congress’s decision not to impose federal employee penalties, in his view, did not clearly bar state ones.
What the Ruling Means for State Immigration Laws
Arizona v. United States remains the framework courts apply whenever a state builds its own immigration enforcement tool. The lines the decision drew are clear enough to work with. States cannot create their own registration crimes. States cannot criminalize conduct Congress deliberately left outside the criminal system. States cannot let their officers make immigration-based arrests outside federal channels. What states can do is share information and verify status during otherwise lawful encounters, so long as they do not stand up a parallel enforcement system that operates on its own.
The decision also exposed a tension that has not gone away. The majority’s reasoning depends on the federal government having a coherent enforcement strategy that state action would disrupt. States that pass laws like SB 1070 typically do so because they believe federal enforcement is inadequate. That disagreement over federal priorities keeps producing state-level immigration legislation in both directions, from restrictionist statutes to sanctuary policies limiting cooperation with federal authorities. Whichever direction the state law runs, this case is where the preemption analysis begins.