Arizona v. United States
Whether key provisions of Arizona's Senate Bill 1070, which created state-level immigration enforcement mechanisms, were preempted by federal immigration law under the Supremacy Clause of the Constitution.
The Decision
5-3 decision · Opinion by Anthony Kennedy · 2012
Majority Opinion— Anthony Kennedyconcurring ↓dissent ↓
In a 5–3 decision authored by Justice Anthony Kennedy (with Justice Kagan recused), the Supreme Court struck down three of the four challenged provisions of SB 1070 as preempted by federal law, while allowing the fourth — the 'show me your papers' provision — to survive for the time being. The ruling was a significant, though not total, victory for the federal government.
The Court struck down Section 3 (making it a state crime not to carry registration papers) on the grounds of field preemption. Justice Kennedy explained that Congress had created a full and complete framework for alien registration in federal law, and that this comprehensive scheme left no room for states to impose their own criminal penalties in the same space. The Court struck down Section 5(C) (criminalizing work by unauthorized immigrants) because Congress had specifically chosen to penalize employers who hire unauthorized workers while deliberately deciding not to impose criminal penalties on the workers themselves. Arizona's law upset that carefully calibrated balance. The Court struck down Section 6 (warrantless arrest authority) because it gave state officers arrest power that went beyond what federal law contemplated and would allow the state to impose its own immigration enforcement priorities, potentially resulting in the prolonged detention of individuals the federal government might choose not to pursue.
The core principle running through the majority opinion was that immigration enforcement is not simply about catching people who have broken the law — it involves complex, interlocking federal judgments about foreign relations, humanitarian concerns, and the allocation of limited enforcement resources. When a state imposes different enforcement methods and priorities, even if the state intends to help, the result is a conflict with the federal government's calibrated approach.
However, the Court upheld Section 2(B) — the requirement that officers check immigration status during lawful stops when there is reasonable suspicion of unlawful presence. The majority reasoned that this provision, on its face, simply required officers to communicate with federal authorities, and that consultation between state and federal officers was already contemplated by existing federal law. But the Court issued a significant caveat: it was too early to tell how the provision would actually be implemented, and if it led to prolonged detentions or racial profiling, it could be challenged later through as-applied litigation. The provision survived only because the Court could not yet say it would necessarily conflict with federal law in practice.
The decision reaffirmed the federal government's dominant role in immigration policy while acknowledging a limited space for state cooperation, establishing important boundaries for state efforts to wade into immigration enforcement.
Concurring Opinions
There were no separate concurring opinions filed beyond the majority opinion itself, though the three partially dissenting justices each concurred in the judgment as it related to Section 2(B), the 'show me your papers' provision that the full Court allowed to stand.
Dissenting Opinions
Antonin Scalia
Justice Scalia argued passionately that states possess an inherent sovereign authority to exclude people from their territory and to protect their borders — a power that predates the Constitution. He contended that Arizona was exercising this fundamental sovereign right and that the federal government's decision not to enforce immigration law could not strip a state of the power to protect itself.
- Before the Constitution was ratified, each state had the undoubted power to exclude noncitizens from its borders, and nothing in the Constitution fully surrendered that power to the federal government.
- The federal government's failure to enforce its own immigration laws — and its affirmative decision to grant deferred action to certain categories of unauthorized immigrants — left Arizona with no effective federal partner, making state action essential.
- If the federal government's mere inaction or policy preferences could preempt state law, then states would be powerless to protect their own residents, a result the Framers never intended.
Clarence Thomas
Justice Thomas argued that none of the four provisions were preempted under a proper, text-based preemption analysis. He rejected what he saw as the majority's overly broad reading of implied preemption doctrine, contending that preemption should be found only where federal and state law directly conflict or where Congress has clearly and explicitly displaced state authority.
- There is no direct conflict between SB 1070's provisions and federal law because the state provisions mirror and reinforce federal requirements rather than contradicting them.
- The majority's expansive approach to implied preemption gave the federal executive branch a de facto veto over state law based on prosecutorial discretion and enforcement preferences, which is not how preemption is supposed to work.
- Courts should require clear evidence that Congress intended to preempt state law rather than inferring preemption from broad notions of federal purposes and policy objectives.
Samuel Alito
Justice Alito agreed with upholding Section 2(B) but dissented from the invalidation of Sections 3 and 5(C), arguing that these provisions did not conflict with the federal scheme. He concurred, however, that Section 6's warrantless arrest authority was properly struck down because it could lead to arrests the federal government had no interest in pursuing.
- Section 3 merely added a state penalty for conduct that was already a federal crime — failing to carry registration documents — and nothing in federal law suggested Congress wanted that requirement to go unenforced at the state level.
- Section 5(C) filled a gap rather than creating a conflict, because Congress's decision to penalize employers who hire unauthorized workers does not logically imply that Congress wanted the workers themselves to face zero legal consequences for seeking that work.
- The majority's preemption analysis was too deferential to executive branch enforcement preferences and not grounded enough in the text and structure of federal statutes.
Background & Facts
In April 2010, Arizona enacted the Support Our Law Enforcement and Safe Neighborhoods Act, widely known as SB 1070. The law was Arizona's high-profile attempt to tackle what state officials described as a crisis of illegal immigration along the southern border. Governor Jan Brewer signed the bill amid heated national debate, and it quickly became a flashpoint in the broader fight over whether states could step into immigration enforcement — traditionally considered a federal responsibility.
Four provisions of SB 1070 were at the center of the legal dispute. Section 3 made it a state crime for immigrants to fail to carry federal registration documents. Section 5(C) made it a state crime for unauthorized immigrants to seek or hold a job. Section 6 authorized Arizona police officers to arrest anyone without a warrant if the officer had probable cause to believe the person had committed a deportable offense. And Section 2(B) — often called the 'show me your papers' provision — required state law enforcement officers to check the immigration status of anyone they lawfully stopped, detained, or arrested if there was reasonable suspicion the person was in the country illegally.
Before SB 1070 could take effect, the United States government filed suit against Arizona in federal court, arguing that the law was preempted by federal immigration law. The federal government contended that immigration regulation is primarily a federal power, and that Arizona's law created an impermissible patchwork of state enforcement that would disrupt the federal government's carefully balanced approach to immigration enforcement, diplomacy, and humanitarian concerns.
The U.S. District Court for the District of Arizona agreed with the federal government and issued a preliminary injunction blocking all four provisions from taking effect. The Ninth Circuit Court of Appeals affirmed that ruling. Arizona then petitioned the Supreme Court, which agreed to hear the case given the enormous national significance of the question — whether states could enact their own immigration enforcement schemes when they believed the federal government was not doing enough.
The case drew intense public attention and dozens of amicus briefs from other states, civil rights organizations, law enforcement groups, and foreign governments. Justice Elena Kagan recused herself, likely because she had been involved with the case as U.S. Solicitor General before joining the Court, leaving eight justices to decide.
The Arguments
Arizona argued that its law merely assisted the federal government in enforcing immigration law and did not conflict with federal authority. The state contended it had sovereign authority to protect its residents from the effects of illegal immigration, especially when the federal government was failing to enforce its own laws adequately.
- States have historically held the power to protect the health, safety, and welfare of their residents, and addressing the consequences of illegal immigration falls within that police power.
- SB 1070 was designed to mirror and complement federal immigration law, not to conflict with it — the state crimes tracked federal requirements, and the status-check provision simply facilitated cooperation with federal immigration authorities.
- Congress had never explicitly barred states from enacting laws like SB 1070, and the federal government's failure to enforce its own immigration laws left Arizona with no choice but to act on its own.
The federal government argued that the Constitution gives the national government broad and exclusive authority over immigration, and that Arizona's law conflicted with the comprehensive federal scheme Congress had created. By imposing its own penalties and enforcement priorities, Arizona was interfering with the federal government's discretion over how, when, and against whom to enforce immigration law.
- The federal government has occupied the field of alien registration through a comprehensive statutory framework, leaving no room for states to impose their own criminal penalties for registration violations.
- Federal immigration enforcement involves sensitive judgments about foreign policy, humanitarian concerns, and prosecutorial discretion — state enforcement schemes like SB 1070 disrupt this careful federal balance.
- Allowing each state to create its own immigration enforcement regime would produce a chaotic patchwork of conflicting laws, undermining the uniformity that the Constitution demands in immigration policy.