An Arizona law that authorizes local law enforcement to enforce immigration laws is preempted by federal law. Arizona law enforcement may inquire about a resident's legal status during lawful encounters, but the state may not implement its own immigration laws. Decided June 25, 2012 (argued April 25, 2012). Opinion of the Court: Anthony Kennedy → go there Topic: Federalism. Arizona v. United States, 567 U.S. 387 (2012), was a United States Supreme Court case involving Arizona's SB 1070, a state law intended to increase the powers of local law enforcement that wished to enforce federal immigration laws. The issue is whether the law usurps the federal government's authority to regulate immigration laws and enforcement. The Court ruled that sections 3, 5(C), and 6 of S. B. 1070 were preempted by federal law but left other parts of the law intact, including a provision that allowed law enforcement to investigate a person's immigration status. Wiki link