LANSING, Mich. (AP) — Voting-rights advocates and a campaign-finance ballot drive group are challenging Republican-enacted requirements that make it harder to qualify proposals for the ballot.

A lawsuit filed Thursday in the Michigan Court of Claims comes a day after Democratic Attorney General Dana Nessel said a law passed in December’s lame-duck session is unconstitutional. Her opinion is binding on state officials, but courts will have the final say.

The law says no more than 15% of petition signatures can be counted from any one of Michigan’s 14 congressional districts.

The suit was filed by the League of Women Voters of Michigan, the ballot committee Michiganders for Fair and Transparent Elections, and individual voters.

They say the law is an unconstitutional attempt by lawmakers to amend the state constitution by statute.