The Supreme Court is set to hear arguments Monday in a case about whether states can force people to prove their U.S. citizenship before registering to vote.
At issue is the legality of Arizona's voter-approved requirement that prospective voters document their U.S. citizenship in order to use a federal registration form that doesn't require such proof.
A federal appeals court threw out that part of Arizona's Proposition 200.
Arizona officials say they should be able to pass laws to stop illegal immigrants and other noncitizens from registering.
Opponents see it as an attack on vulnerable voter groups such as minorities, immigrants and the elderly.
Alabama, Georgia, Kansas and Tennessee have similar requirements, while 12 other states are contemplating similar legislation.