State immigration enforcement

1. The Federal Government’s broad, undoubted power over immigration and alien status rests, in part, on its constitutional power to “establish an uniform Rule of Naturalization,” Art. I, §8, cl. 4, and on its inherent sovereign power to control and conduct foreign relations, see Toll v. Moreno, 458 U. S. 1, 10. Federal governance is extensive and complex. 2. The Supremacy Clause gives Congress the power to preempt state law. A statute may contain an express preemption provision, see, e.g., Chamber of Commerce of United States of America v. Whiting, 563 U. S. ___, ___, but state law must also give way to federal law in at least two other circumstances. First, States are precluded from regulating conduct in a field that Congress has determined must be regulated by its exclusive governance. See Gade v. National Solid Wastes Management Assn., 505 U. S. 88, 115. 3. Sections 3, 5(C), and 6 of S. B. 1070 are preempted by federal law. 4. It was improper to enjoin §2(B) before the state courts had an opportunity to construe it and without some showing that §2(B)’s enforcement in fact conflicts with federal immigration law and its objectives. 641 F. 3d 339, affirmed in part, reversed in part, and remanded.

The Court said the federal government has broad authority over immigration and that federal law can override state rules in areas Congress has reserved. It found Sections 3, 5(C), and 6 were overridden, but Section 2(B) could not be blocked before Arizona courts interpreted it and a conflict was shown.

The case returned to the lower court for further proceedings. A future block on Section 2(B) would require Arizona courts to interpret it and a showing that its enforcement actually conflicts with federal immigration law.