The U.S. Supreme Court will hear arguments soon on Arizona's 2004 voter-approved requirement that residents show proof of citizenship when they register to vote.

The Arizona Republic reports that state attorneys will ask the high court on March 18 to overturn a 9th Circuit Court of Appeals ruling.

That ruling said Arizona cannot require voters to provide documents when registering with the federal form, but it can require voters registering with the state form to do so.

Among its provisions, the National Voter Registration Act creates a standard federal registration form that all states must accept. It requires applicants to sign a statement that they are citizens, but it doesn't require them to show any proof.

Arizona was the first state to require voters to show proof of citizenship.