Arizona v. United States

Following is the case brief for Arizona v. United States, 567 U.S. 387 (2012)

Case Summary of Arizona v. United States:

  • The State of Arizona passed a State immigration law in 2010, responding to the problem of illegal immigration in the State.
  • The United States sued in federal court to enjoin enforcement of the law.
  • The federal district court enjoined four provisions of the act that (i) made it a crime to be unlawfully present in the State; (ii) made it a crime to work, or seek work, if illegally in the U.S.; (iii) authorized warrantless arrests of people based on suspicion of being illegally in the U.S.; (iv) required State and local officers to check the citizenship of people they arrested.
  • The Ninth Circuit Court of Appeals affirmed the district court’s decision.
  • The U.S. Supreme Court affirmed the Ninth Circuit’s decision for the first three provisions as preempted by federal law, but reversed on the fourth as not in conflict with federal law.

Arizona v. United States Case Brief

Statement of the Facts:

In 2010, the State of Arizona passed a bill, commonly referred to as S.B. 1070.  The bill was meant to address the increasing problem of illegal immigrants coming into the State.  The bill had four prominent provisions, as follows:

  1. It was a state crime to fail to comply with federal alien-registration requirements.
  2. It was a state crime for an immigrant unlawfully in the country to seek or engage in work in Arizona.
  3. State and local officers had the authority to arrest people without a warrant if they had “probable cause to believe [an individual] has committed any public offense that makes the person removable from the United States.”
  4. Officers conducting a stop, detention, or arrest should make efforts to verify the person’s immigration status with the federal government.

The United States government filed suit in federal district court to enjoin Arizona from enforcing the entire S.B. 1070 law.  The government claimed that the Arizona law was preempted by federal law.

Procedural History:

  • The federal district court enjoined enforcement of the four prominent provisions noted above.
  • The Ninth Circuit affirmed the federal district court’s decision.
  • The U.S. Supreme Court granted certiorari.

Issue and Holding:

Were the four provisions of Arizona’s S.B. 1070 law preempted by federal immigration law?  Yes, with the exception of the last provision.


The decision of the Ninth Circuit Court of Appeals is affirmed in part and reversed in part.

Rule of Law or Legal Principle Applied:

A State cannot try to pass State immigration laws that are preempted by, or run in conflict with, federal immigration law because the federal government possesses the ultimate authority over immigration law and policy.


The Federal Government has “broad, undoubted power” over immigration based on the Constitution.  The Supremacy Clause gives Congress the power to preempt state law expressly, or when it is clear federal law either was intended to “occupy the field” on a particular area or it conflicts with a state law.

  1. Crime of unlawful presence. This portion of the Arizona law intrudes on the field of alien registration in which Congress left no room for the State to regulate.
  2. Crime of illegal immigrant seeking work. Congress, in focusing on punishing employers for hiring illegal immigrants, demonstrates that it chose not to focus on punishing employees, or those seeking employment.  Arizona’s law to the contrary cannot stand.
  3. Warrantless arrests on suspicion of removability. It is not a crime for a removable immigrant to remain in the U.S.  While cooperation between state and federal law enforcement is encouraged, Arizona’s law goes too far by allowing state officials to act unilaterally.
  4. Citizenship check. This provision does not run afoul of federal immigration law, because the people in question are already lawfully detained, and the citizenship check is properly limited.  The Court should not enjoin this provision until Arizona courts have an opportunity to interpret it.

Concurring and Dissenting Opinions:

Concurring in Part, Dissenting in Part (Scalia):

All four provisions are constitutional.  The Arizona law does not conflict with federal law.  Rather, it enforces federal immigration law more effectively.  States should be permitted to engage in the defining characteristic of their sovereignty, excluding people from their territory if they have no right to be there.

Concurring in Part, Dissenting in Part (Thomas):

All four provisions are constitutional.  There is simply no conflict between the ordinary meaning of federal immigration law and the Arizona statute.

Concurring in Part, Dissenting in Part (Alito):

The Court is correct that the “crime of unlawful presence,” is preempted by federal law, and that the “citizenship check” is not preempted.  However, the Court departed from DeCanas v. Bica, 424 U.S. 351 (1976), in finding that the State could not punish employees for seeking work while being illegally in the country.  Also, the Court was wrong to find the “warrantless arrest” provision unconstitutional.  The State already can arrest someone without a warrant based on probable cause that he or she committed a crime.


Arizona v. United States is a significant case because it addressed squarely what many at the time believed were draconian laws directed at a vulnerable population – illegal immigrants.  There was a particularly vociferous uproar in the public debate about allowing police to arrest people for simply suspecting that those people were undocumented.

Student Resources:

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