According to the Detroit News, a group called “Fair Lines America Foundation” filed suit today in Federal District Court in Grand Rapids to block implementation of the Michigan Citizens Redistricting Commission, passed by Michigan voters in 2018 by a 61% — 39% margin. The Commission will be made up of three groups: four members who affiliate with Republicans, four Democrats, and five who affiliate with no party. Elected officials, party officials and their immediate families are not eligible.
It is this last aspect that Fair Lines, a non-profit connected to the National Republican Redistricting Trust, is basing their suit on. They claim that this makes the Commission discriminatory.
Michigan currently has one of the top five Republican gerrymanders out of all the states in place, and naturally they want to keep it that way, having a gerrymandered Republican majority pick their new district lines to keep the party going. Secretary of State Jocelyn Benson, a Democrat elected in 2018 is the defendant, and Attorney General Dana Nessel, another 2018 Democrat will be conducting / overseeing the defense on behalf of the state.
In 2018 a group connected to the Michigan Chamber of Commerce sued to keep the proposal off the ballot, but the Michigan Supreme Court decided to leave it in place. Given that this was a Constitutional Amendment, and hence facially Constitutional, the Republicans are giving up on state courts and filing a Federal lawsuit instead.