Arizona v. United States

Arizona v. United States, 567 U.S. ___ ( 2012 ), a US Supreme Court case decided by a 5–3 vote (Justice Elena Kagan did not participate), held that federal law preempted crucial provisions of S.B. 1070, the Arizona “Support Our Law Enforcements and Safe Neighborhoods Act,” while leaving for further litigation the legal and constitutional status of the most controversial provision of that bill. The decision did not explicitly rule that state efforts to regulate illegal immigration were unconstitutional per se, but that Arizona's efforts were inconsistent with existing federal policy. Nevertheless, a close reading of Justice Anthony Kennedy's majority opinion suggests that the most popular state regulatory efforts are likely to be struck down on either preemption or constitutional grounds, unless there is a substantial change in federal immigration policy or the composition of the Supreme Court.


S.B. 1070 was the strongest state regulation involving illegal immigration at the time the bill was passed in 2010. The most controversial provision of the bill permitted state police officers to detain any person they suspected of being an illegal immigrant. Other controversial provisions established a state crime for failing to comply with federal registration requirements, punished illegal aliens for seeking work in Arizona, and authorized state officials to make warrantless arrests of persons they believed might be deportable under federal law. Proponents of these provisions insisted that they were necessary in light of weak federal efforts to police illegal immigration. Opponents insisted that Arizona was acting on the basis of racial stereotypes and licensing police officers to engage in racial stereotyping when determining whether a person might be subject to deportation as an illegal alien.

Unlike many civil rights and civil liberties policies, immigration reform partly cuts against the hyperpartisan trends in American politics today. Republicans tend to favor stricter state policies on illegal immigrants than Democrats. Nevertheless, Republicans in states with large Hispanic populations condemned S.B. 1070, while Democrats in states with significant numbers of illegal immigrants often praised similar measures.

The Barack Obama administration, encouraged by many pro-immigration groups, asked a lower federal court to enjoin enforcement of S.B. 1070 on the grounds that the measure was preempted by federal law and that states have no power to regulate immigration. The preemption doctrine holds that states may not act inconsistently with federal law. State laws may not require that people act inconsistently with federal law or permit actions that, while not inconsistent with federal law, might nevertheless interfere with the objections of federal law. If the federal government declares the speed limit on interstate highways shall be 60 miles per hour, states cannot mandate a 65-mile-per-hour speed limit, because they would permit people to drive faster than permitted by federal law or, in all likelihood a 55-mile-an-hour speed limit, because they would defeat the purpose of having a uniform speed limit on national highways.

Undocumented Mexican immigrants crossing the Sonoran desert on their way to work in Tucson, Arizona, January 2011.

Undocumented Mexican immigrants crossing the Sonoran desert on their way to work in Tucson, Arizona, January 2011.

The “exclusive power” doctrine mandates that Article I's grant of some powers to the federal government serves to take from or deny those powers to states. If Article I declares that the federal government shall regulate immigration, then states may not. Not all Article I powers, however, are exclusive. Both the federal and state governments, for example, may levy taxes.


Justice Kennedy's majority opinion focused on the preemption issues. He began by pointing to the three circumstances in which preemption occurs: (1) Congress may explicitly forbid certain state laws; (2) the federal regulation may be so “pervasive” as to leave “no room for States to supplement”; or (3) the matter must be regulated exclusively by Congress. The Court ruled that federal law preempted the state registration requirement because the registration framework adopted by Congress occupied the entire field of alien registration, which made “even complementary state regulation … impermissible.” S.B. 1070's effort to criminalize illegal aliens who sought work was also preempted on the ground that Congress had established a “comprehensive frame-work for combatting the employment of illegal aliens” and had self-consciously decided not to punish illegal aliens for seeking work. The Arizona provision permitting state officers to arrest aliens who they believed were deportable was similarly held to conflict with “the principle that the removal process is entrusted to the discretion of the Federal Government.”

Justice Kennedy did, however, claim that the preemption doctrine did not mandate overturning S.B. 1070's requirement that state police officers attempt to determine the immigration status of the persons they detain on other grounds when some reason exists for thinking the detainee is an illegal alien. Such persons, he pointed out, were first detained for legitimate state reasons. In such circumstances, state officials would be assisting rather than interfering or attempting to supplement federal immigration efforts. Kennedy worried that the law might be applied unconstitutionally, but he believed that was a matter for future litigation to determine.


Justice Antonin Scalia's dissent worked from a different first principle. He insisted that “as a sovereign, Arizona has the inherent power to exclude persons from its territory.” In sharp contrast to Kennedy, who maintained that immigration should primarily be a federal policy, Scalia insisted that states had traditionally regulated immigration. Hence, he thought, unless federal law either clearly prohibited the state law, or the state law was clearly inconsistent with federal law, no preemption problem existed. Since Scalia concluded that neither was the case with any provision of S.B. 1070, he would have had the Supreme Court sustain the entire law. Justices Clarence Thomas and Samuel Alito largely joined with the Scalia dissent, although Justice Alito thought that federal law preempted the state requirement of alien registration. In a vote that surprised many observers, Chief Justice John Roberts, who is normally sympathetic to state sovereignty claims, silently joined the majority opinion. The significance of that vote remains unknown.

As of 2014, Arizona v. United States is the most recent Supreme Court decision on state power to regulate illegal immigration. Given that the five-justice majority included Justice Kennedy and Chief Justice Roberts, the high probability exists that any substantial state effort to impose restrictions on illegal immigration will be held preempted by federal law. That Justice Kagan, who recused herself in Arizona, supported the Obama administration's effort to strike down S.B. 1070, strengthens the durability of this precedent. Nevertheless, the constitutional politics of immigration reform remain volatile. New federal policies more sympathetic to state regulation and the next round of judicial appointments could result in new justices more sympathetic to state regulation.

SEE ALSO Federal Powers: Immigration and Naturalization ; Federalism, Theory of ; Preemption ; Roberts, John .


Chacón, Jennifer M. “Policing Immigration after Arizona.Wake Forest Journal of Law and Policy 3, no. 2 (2013): 231–48.

Guttentag, Lucas. “Immigration Preemption and the Limits of State Power: Reflections on Arizona v. United States.Stanford Journal of Civil Rights and Civil Liberties 9, no. 2 (2013): 1–46.

Mark A. Graber
University of Maryland Carey School of Law