LITTLE ROCK, Ark. (AP) — Supporters of an effort to make Arkansas’ GOP primaries open only to registered Republicans have filed a lawsuit over state party officials blocking that proposal.

The lawsuit filed in federal court on Monday stems from delegates at the state Republican Party convention voting to allow only registered GOP voters to participate in the party’s primary. The party’s executive committee in July nullified that proposal and several other actions by the convention, saying proper steps weren’t taken to consider them.

The lawsuit filed by about two dozen of the convention delegates asks a federal judge to order the state GOP and Secretary of State John Thurston to close the state’s primary election.

State Party Executive Director Seth Mays said the Republican Party of Arkansas will defend the party’s rules “to the fullest extent of the law.”

Thurston’s office said it was reviewing the lawsuit but declined to immediately comment.

Voters in Arkansas aren’t required to choose a party when they register, and the majority of voters don’t pick Republican or Democratic.