Arizona v. United States
The Supreme Court struck down three parts of Arizona's immigration law—making it a state crime to work without authorization, to fail to carry federal registration papers, and letting police arrest people believed removable—because federal law controls those areas.
But the Court let stand, for now, the provision requiring police to check the immigration status of people they lawfully stop when they suspect the person is in the country unlawfully, saying it was too soon to strike it down before Arizona courts had interpreted it.
“This is not the system Congress created.”
Explaining why Arizona's broader arrest authority for suspected removability conflicted with the federal removal scheme.
How it got here: The federal government sued to block Arizona's law before enforcement; a federal district court and the Ninth Circuit both blocked four provisions as likely preempted; Arizona asked the Supreme Court to review.
The Case in Depth
What happened
In 2010, Arizona passed S.B. 1070 to address the large number of people in the state without legal immigration status. The law made it a state crime to fail to carry federal registration papers or to seek work without authorization, and gave police new power to arrest people believed to be removable and to check immigration status during lawful stops. The federal government sued to block the law before it took effect, arguing it interfered with federal immigration authority.
The question before the Court
Could Arizona enforce its own tough immigration provisions—like making unauthorized work a crime and giving police new arrest powers—alongside federal immigration law?
Why it matters
The ruling limited how far states can go in writing their own immigration enforcement laws, reinforcing that immigration policy is primarily a federal responsibility. It let Arizona keep its most controversial 'status check' provision for now, but signaled that other states copying Arizona's approach to criminalizing unauthorized work or presence would likely face the same legal limits.
What changes now
The case returns to the lower courts for further proceedings. Sections 3, 5(C), and 6 remain blocked as preempted. Section 2(B) can go into effect, though the Court left open the possibility of future challenges once Arizona courts interpret the provision or once real-world enforcement reveals conflicts with federal law or constitutional problems.
What this does not decide
The Court did not decide whether Section 2(B) is constitutional in practice, including whether it might lead to unreasonably long detentions in violation of the Fourth Amendment. It also left open future legal challenges to Section 2(B) once state courts interpret it and once actual enforcement can be evaluated.
Concurrences and dissents
Dissent in part — Justice Scalia
“If securing its territory in this fashion is not within the power of Arizona, we should cease referring to it as a sovereign State.”Scalia's closing argument that Arizona retains an inherent sovereign right to protect its borders.
Justice Scalia argued Arizona, as a sovereign, retains an inherent power to exclude people from its territory that the Constitution never stripped away, and that none of the four provisions should have been preempted. He rejected the majority's field-preemption reasoning as insufficient to eliminate this core sovereign power and would have upheld Sections 3, 5(C), and 6 as consistent with federal law.
Dissent in part — Justice Thomas
Justice Thomas agreed no provision should be preempted, but for a narrower reason: preemption should turn only on whether the literal text of state and federal law conflict, not on judicially inferred congressional 'purposes and objectives.' Applying that textual approach, he found no genuine conflict between Arizona's law and the relevant federal statutes.
Dissent in part — Justice Alito
Justice Alito agreed with the majority that Sections 2(B) and 3 were properly handled, but disagreed on Sections 5(C) and 6. He argued Section 5(C) intruded on the traditional state power to regulate employment, which Congress had not clearly displaced, and that Section 6 added little to arrest authority states already possessed and did not conflict with federal law.
How the Court got there
The legal reasoning, step by step
- The Court applied two preemption principles: field preemption, where Congress has occupied an area so completely that states may not regulate it at all even in a complementary way, and obstacle preemption, where a state law conflicts with federal law by standing in the way of Congress's full purposes and objectives.
- Relying on Hines v. Davidowitz, a 1941 decision striking down a state alien-registration law, the Court found federal law creates a complete, all-embracing system for registering immigrants, so Arizona's parallel criminal registration provision (Section 3) intruded on ground Congress had reserved entirely for itself.
- For the work-authorization provision (Section 5(C)), the Court found that Congress, in writing the federal law regulating employment of unauthorized workers, deliberately chose to punish employers but not employees with criminal penalties, so a state law criminalizing work by unauthorized immigrants stood as an obstacle to that considered balance.
- For the arrest provision (Section 6), the Court found federal law carefully limits when officers may make warrantless arrests based on suspected removability, and letting state officers arrest people on broader grounds without federal input would let a state pursue its own immigration policy in conflict with the discretion Congress gave federal officials.
- For the status-check provision (Section 2(B)), the Court concluded that requiring police to verify immigration status during lawful stops does not itself conflict with federal law, since Congress has encouraged such information-sharing, and it was too soon to assume the provision would be applied in a way that created a real conflict before state courts had interpreted it.
Doctrinal impact
Cases affected by this decision
Reaffirms Hines v. Davidowitz (312 U. S. 52)
The Court relied on Hines to hold that federal law completely occupies the field of alien registration.
Distinguishes De Canas v. Bica (424 U. S. 351)
The Court said De Canas no longer controls because Congress has since enacted a comprehensive federal employment scheme.