JUNEAU (AP) — Alaska Democrats have sued the state after Lt. Gov. Byron Mallott denied the party’s request to allow candidates not affiliated with a political party to run in the Democratic primary.

The lawsuit, filed Monday, challenges as unconstitutional a state law that requires a candidate seeking a party’s nomination to be a registered voter of that party. It says the law interferes with the party’s constitutional right to freedom of association and wants a state court judge to block enforcement of it.

Alaska Department of Law spokeswoman Cori Mills said by email that the state typically defends its laws unless they are clearly unconstitutional. The department is reviewing the complaint and would have no further comment at this time, she wrote.

The party last month adopted a rule change to allow unaffiliated candidates to run in the Democratic primary and compete for the party’s endorsement. Party leaders said this was a way to be more inclusive. The party asked state election officials to implement the change for this year’s elections. As part of the request, state party chair Casey Steinau raised constitutional questions about the candidacy law and said the party believed it to be unenforceable.

In a written response to the party’s request last week, Mallott, a Democrat who oversees elections in Alaska, said it’s up to a court to decide whether a law is ultimately constitutional. Mallott said the state intends to follow the law as it stands.

Steinau said the party already allows voters registered as nonpartisan and undeclared to participate in the Democratic primary. Allowing unaffiliated candidates into the primary would be a natural progression, she said.

The party wants to put forth the strongest candidates that share its values, Steinau said.

In running for governor in 2014, Bill Walker changed his party affiliation from Republican to undeclared in joining forces with Mallott, who gave up his gubernatorial bid to be Walker’s running mate. The ticket was supported by the Democratic Party.

The state’s lone unaffiliated state lawmaker — Rep. Dan Ortiz of Ketchikan — caucuses with House Democrats.