(CNN) A federal appeals court on Wednesday affirmed a lower court's decision that a Kansas voting law, crafted by conservative hardliner and former Kansas Secretary of State Kris Kobach, is unconstitutional and violates the National Voter Registration Act.

The law, which took effect in 2013, required anyone who registers to vote in the state to provide documentation of US citizenship such as a birth certificate or a passport.

The decision is the latest in a series of defeats for the legislation, which, according to the American Civil Liberties Union, blocked more than 30,000 Kansans from registering to vote.

A federal district court had struck down the law after finding that it violated the Constitution and the National Voter Registration Act. The state then appealed to the 10th US Circuit Court of Appeals.

The three-judge panel on the appeals court wrote they were not persuaded by Kansas' argument that there was a problem of noncitizens attempting to register to vote.

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