A U.S. elections agency must remove a proof-of-citizenship requirement from a mail-in federal voter registration form used for November’s election in Kansas, Alabama and Georgia, a federal appeals court panel in Washington ordered late Friday, reversing a lower court.

The 2-to-1 decision by the U.S. Court of Appeals for the District of Columbia Circuit came one day after civil rights groups in oral arguments said the provision could disenfranchise tens of thousands of U.S. citizens applying to vote in Kansas without required papers.

Kansas is the only state enforcing a demand to show documentation such as a birth certificate, passport or naturalization papers instead of accepting signed and sworn affirmation of citizenship to register to vote in federal races.

U.S. Appeals Court Judges Judith Rogers and Stephen Williams granted a preliminary injunction while a lawsuit by the League of Women Voters and other groups against the document requirement is pending, saying the voter groups had shown “irreparable harm” caused by the change and were likely to prevail once the case is decided.

The court set aside a June 29 decision by U.S. District Judge Richard Leon that denied an injunction and returned the case to him to decide. A hearing on the case is set for Monday.

The order was the latest victory for civil rights groups, Democratic lawyers and the Obama administration, who have asked federal appeals courts to knock down new voting laws passed in Texas, North Carolina and other states – part of their ongoing battle with conservative lawyers and Republican lawmakers over voter eligibility.