(AP) — The American Civil Liberties Union has notified Kansas Secretary of State Kris Kobach that it intends to file a federal lawsuit over a state law requiring new voters to provide proof of their U.S. citizenship.

The ACLU sent Kobach a notice Tuesday, telling him that Kansas is not in compliance with federal election laws because it requires new voters to provide a birth certificate, passport or other acceptable document.

Federal law requires someone to give state officials 90 days’ notice of a potential lawsuit.

The ACLU argued that states must allow people to register to vote at driver’s license offices and can’t add a proof-of-citizenship requirement.

More than 14,000 prospective Kansas voters have their registrations in “suspense” because they’ve filled out registration forms but not provided proof of citizenship.