Arizona's Proposition 200 required prospective voters to submit documentary proof of citizenship even when registering with the federal 'motor voter' form the National Voter Registration Act prescribes. Justice Scalia's opinion held that the Elections Clause of Article I, § 4 gives Congress broad authority to set the 'Manner' of federal elections, and the NVRA's command that states 'accept and use' the federal form preempts additional state documentation requirements at the registration stage. States retain other tools — such as separately verifying citizenship through databases — but they cannot rewrite the federal form. The case is the leading modern precedent on federal preemption in election administration.