LANSING, Mich. (AP) — Republicans sued Tuesday to block the creation of Michigan’s new, voter-approved redistricting commission, challenging eligibility guidelines that prohibit politicians and others from serving on the panel.

The lawsuit, filed in federal court and praised by a national GOP group whose finance chairman is former Wisconsin Gov. Scott Walker, says the provisions violate potential applicants’ rights to free speech and equal protection under the law.

The 2018 constitutional amendment requires that a commission of four self-identified Democrats, four self-identified Republicans and five unaffiliated members draw congressional and legislative lines instead of the Legislature, starting in 2021. It was a bid to curtail gerrymandering in a state where the GOP has had one of the largest partisan legislative advantages in the country after controlling the once-a-decade process in 2011.

Michigan is among five states where Republicans retained control of the state House even though Democratic candidates won more votes statewide last fall.

Those excluded from serving on the panel include people who currently are or have in the previous six years been elected partisan officials or candidates, their paid consultants or employees, legislative workers, lobbyists and their employees, or political appointees not subject to civil service classification. Also barred from the paid positions are those individuals’ parents, children and spouses.

“In excluding certain categories of citizens from eligibility based on their exercise of core First Amendment rights, including freedom of speech, right of association, and right to petition the government, the State has unconstitutionally conditioned eligibility for a value benefit on their willingness to limit their First Amendment right to petition government,” says the suit, which was brought by 15 Republicans including state Sen. Tom Barrett and various party officials with financial support from Fair Lines America, a nonprofit with ties to the National Republican Redistricting Trust, for which Walker is fundraising. They say there is no “compelling explanation” as to how limiting participation would result in a more impartial panel.

They want a judge to declare the law unconstitutional and prevent Democratic Secretary of State Jocelyn Benson from selecting commissioners, which are to be chosen randomly by September 2020 following a multi-step process.

“Voters spoke loud and clear last November that they want an independent, citizen-led commission — not partisan politicians — responsible for drawing district lines,” she said in a statement. “My office will stay focused on engaging the public and encouraging full participation in a transparent application and random selection process for this commission, which has the opportunity to map Michigan’s future.”

Voters Not Politicians, the group that spearheaded the ballot measure, criticized the suit but called it no surprise that politicians want to hold onto their power.

“Michigan is one of the most gerrymandered states in the nation, but voters pushed back by overwhelmingly supporting the new redistricting amendment so voters choose their politicians — not the other way around,” said Jamie Lyons-Eddy, the organization’s director of campaigns and programs. “We’re confident that the proposal will survive any and all legal challenges, just as it did from many of these same politicians on the way to the ballot.”

One of the people suing is Tony Daunt, a lobbyist and executive director of the conservative Michigan Freedom Fund who also sits on the state GOP committee. His group said at least half a million residents would be “disenfranchised.”

“Michigan residents’ constitutional rights do not end when their son or mother decides to take a new job or to represent their neighborhood at a local political party meeting,” Daunt said.

Michael Li, a redistricting lawyer with the Brennan Center for Justice — which opposes gerrymandering — said 13 states now have some form of a redistricting commission for congressional or legislative mapmaking, or both. Of those, 10 restrict who can serve while two others’ panels have elected officials. Just one state outside Michigan — Iowa — prohibits relatives of excluded individuals from participating, he said.

Li said he was not aware of any similar challenge having been filed previously in other states. He called the legal theory “very novel.”

“It varies from state to state, but almost every state has some form of restriction to make sure people aren’t too closely connected to the political process,” said Li, contending that Michigan’s qualification standards are not different from laws that say candidates for office have to be a minimum age to run. “There are always some people who are excluded from participating on government bodies. It doesn’t mean they can’t participate in other ways.”