MADISON, Wis. » Federal judges struck down Wisconsin’s Republican-drawn legislative districts as unconstitutional today, marking a victory for minority Democrats that could force the Legislature to redraw the maps.

The 2-1 ruling by a three-judge panel can be appealed to the U.S. Supreme Court. It gives hope to legislative Democrats who have been in the minority for six years and lost more ground in this month’s election. The judges didn’t order any immediate changes to district boundaries, instead saying they would accept ideas from state attorneys and the group of voters who challenged the districts on what to do next within the next 30 days.

The lawsuit focuses on Assembly districts, but since Senate districts are based on the Assembly maps it invalidates the maps for both chambers.

“The court has clearly indicated the map is unconstitutional and that Wisconsin citizens deserve a fair map,” said Sachin Ccheda, director of the Fair Elections Project, which organized the lawsuit. “We’re confident this is the first step in democracy being restored to the people of Wisconsin.”

A spokesman for the state Department of Justice, which defended the boundaries, didn’t immediately return a message seeking comment. A spokeswoman for Republican Senate Majority Leader Scott Fitzgerald referred questions to justice department. Republican Gov. Scott Walker’s spokesman, Tom Evenson, had no immediate comment, saying only that Walker’s office was reviewing the decision.

Republicans drew the maps in 2011 after they took full control of state government in the 2010 elections. Assembly Republicans didn’t lose a seat and defeated a Democratic incumbent in this month’s elections to gain their largest majority in the chamber since 1957. Senate Republicans also didn’t lose a single seat and defeated a Democratic incumbent to gain their largest majority since 1971.

A dozen voters sued in July 2015, arguing the maps unconstitutionally discriminated against Democrats by diluting their voting power. They called it the worst example of gerrymandering in modern history.

Attorneys for the state said the redrawn districts simply reflected that Wisconsin was trending Republican, and argued there is no legal way to measure gerrymandering — the process of dividing districts to gain an unfair advantage.

The ruling came from a panel of three judges — U.S. District Judge Barbara Crabb, 7th U.S. Circuit Court of Appeals Judge Kenneth Ripple and U.S. District Judge William Griesbach. Griesbach was appointed by Republican President George W. Bush, Ripple by Republican President Ronald Reagan and Crabb by Democratic President Jimmy Carter.

During a four-day trial in May, the voters’ attorneys argued that the boundaries represented the worst example of gerrymandering in modern history. They said the maps aimed to marginalize Democrats by packing them into districts that already favored them — thus leading to a lot of wasted votes that could have helped Democrats elsewhere. One effect of the redistricting, according to plaintiff attorney Gerald Hebert, was to reduce the number of swing districts from 19 to 10. The voters also noted that under the new maps in 2012, Republicans won 60 of 99 Assembly seats even though Democrats won a majority of the statewide vote.

State attorneys argued that partisanship should be expected when one party draws legislative boundaries.

The U.S. Supreme Court has yet to come up with a legal standard for deciding when redistricting becomes unconstitutional gerrymandering. Plaintiff attorneys hoped to establish a new method for measuring partisanship that could be used to challenge voting maps around the country.

They offered the judges an equation that included measuring and comparing each party’s wasted votes in an election. State lawyers argued the equation lacked any constitutional basis and there was no way a court could measure gerrymandering.

The majority of the panel — Crabb and Ripple — accepted the equation.

“We find that (the maps were) intended to burden the representational rights of Democratic voters throughout the decennial period by impeding their ability to translate their votes into legislative seats,” Ripple wrote. “We find that the discriminatory effect is not explained by the political geography of Wisconsin nor is it justified by a legitimate state interest.”

Assembly Minority Leader Peter Barca called today’s ruling a “historic victory for voters.”

“Voters should be able to choose their representatives, not the other way around,” Barca said.

Griesbach wrote in dissent that the Republicans’ maps were politically motivated but comply with traditional redistricting principles. Republicans likely would have retained control of the Assembly and Senate in the 2012 and 2014 elections without the new maps, he said.