The US Supreme Court on Thursday revived part of an Arizona voter law requiring documented proof of US citizenship to register to vote, in response to a request from the Republican National Committee and Arizona Republicans.

The justices in a 5-4 ruling agreed to reinstate a provision of the law after a federal judge blocked it in response to legal challenges by Democratic President Joe Biden's administration and advocacy groups.

The decision comes before the November 5 election in which Democratic Vice President Kamala Harris is facing off against Republican former President Donald Trump, who continues to falsely claim that his 2020 election defeat was the result of fraud.

Arizona's Republican-controlled legislature adopted new restrictions on voter registration in 2022. The law requires applicants who submit a federal registration form to provide evidence of US citizenship to vote in presidential elections or vote by mail in any federal election.

Voter registrants who use a separate, state-created form face even tighter restrictions. Without proof of US citizenship, state applications are rejected in their entirety, and officials who fail to do so face a minor felony charge under the law.

The Supreme Court's ruling revived the restriction related to the state voter registration form, but kept intact a judicial decision blocking the provision that sought to tighten limits on the federal form.

Chief Justice John Roberts joined with fellow conservative Justices Brett Kavanaugh, Clarence Thomas, Samuel Alito and Neil Gorsuch to grant Republicans' request in part, though Thomas, Alito and Gorsuch indicated they would have granted the entire request.

Liberal Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson, along with conservative Justice Amy Coney Barrett, would have denied the request in full. (Reuters)