Arizona's law requiring concrete evidence of citizenship before someone may register to vote is pre-empted by the National Voter Registration Act, ruled the U.S. Supreme Court on Monday.

The 1993 federal law mandates that states "accept and use" a federal registration form, which only requires the registrant to attest to citizenship. Arizona required voter registration officials to reject any application, including the federal form, that did not have documentary evidence of citizenship. "We conclude that the fairest reading of the statute is that a state-imposed requirement of evidence of citizenship not required by the federal form is 'inconsistent with' the NVRA's mandate that states 'accept and use' the federal form," wrote Justice Antonin Scalia for a 7-2 majority in Arizona v. Inter Tribal Council of Arizona.