The law, which came into effect in 2013 and was later blocked by a federal court, has been championed by former Secretary of State of Kansas Kris Kobach, who was appointed by President Donald Trump to contribute to the study of voter fraud. Under the law, residents needed to present a document to prove their citizenship before they could register to vote.
According to the ruling, there was no evidence that the integrity of the state's electoral process had been jeopardized or that voter fraud had taken place.
'The documentary proof of citizenship (DPOC) violated ... the National Voter Registration Act", the ruling said. 'We conclude that the DPOC requirement unconstitutionally burdens the right to vote."
The court's decision is also binding in Oklahoma, New Mexico, Colorado, Wyoming, and Utah, and partially in Montana and Idaho.
The National Voter Registration Act of 1993 requires that all states allow citizens to register to vote by mail. In addition, each voter registration application must allow the applicant to declare they are US citizens under penalty of perjury for submitting a false declaration, according to the Justice Department.