Kansas and Arizona filed a lawsuit jointly against the federal government Wednesday over requirements needed to register to vote.

The lawsuit demands that the U.S. Elections Assistance Commission modify the federal voter registration form in both states so it would allow for proof of citizenship when people sign up to vote.

The federal form doesn’t require proof of citizenship. It only requires prospective voters to declare that they are citizens.

“A mere oath without concrete evidence of citizenship, as allowed for by the current version of the Federal Form, does not suffice to effectuate the State laws of Plaintiffs or enable Plaintiffs to obtain information Plaintiffs deem necessary to assess the eligibility of voter registration applicants and to enforce their voter qualifications,” the lawsuit reads.