The U.S. Supreme Court sided with tribal interests today in Arizona v. Inter Tribal Council of Arizona, a voting rights case.

By a vote of 7-2, the court held that certain provisions of Proposition 200 are pre-empted by federal law. That means the state can't ask people to prove their U.S. citizenship when they register to vote.

The Inter-Tribal Council of Arizona and the Hopi Tribe were among the plaintiffs that challenged the law. The tribes want to protect the voting rights of members who were born in the U.S. but might lack proper documentation.

The National Voter Registration Act already asks about citizenship, the Supreme Court noted. So the state's requirement conflicts with federal law.

"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," Justice Antonin Scalia wrote for the majority.

Supreme Court Decision:
Arizona v. Inter Tribal Council of Arizona (June 17, 2013)

Supreme Court Oral Argument Transcript:
Inter-Tribal Council of Arizona v. Arizona (March 18, 2013)

9th Circuit Decision:
Inter-Tribal Council of Arizona v. Arizona (April 17, 2012)

Related Stories:
Supreme Court takes up tribal challenge to Arizona voter law (3/19)
Supreme Court set to hear tribal challenge to Arizona voter law (3/12)
Editorial: Voting Rights Act necessary to prevent discrimination (3/12)
Supreme Court to review Arizona voter law that tribes oppose (10/16)