A federal court ruled today that voting districts drawn by Wisconsin Republicans are unconstitutional. The ruling is a major victory for state Democrats who have been in the minority for six years and lost even more ground in the recent election. A three-judge panel tossed maps drawn by Republican lawmakers five years ago, saying that they violate the voting rights of Democrats.

Critics have argued that Wisconsin Assembly’s district map is unconstitutional because it was drawn in such a way that some voters’ ballots are meaningless. Some districts are carved up in such a way that they are dominated by Republicans and the plaintiffs argue that Democrats’ voting power in those districts is muted.

The court wrote: “We find that Act 43 was intended to burden the representational rights of Democratic voters throughout the decennial period by impeding their ability to translate their votes into legislative seats. Moreover, as demonstrated by the results of the 2012 and 2014 elections, among other evidence, we conclude that Act 43 has had its intended effect. Finally, we find that the discriminatory effect is not explained by the political geography of Wisconsin nor is it justified by a legitimate state interest. Consequently, Act 43 constitutes an unconstitutional political gerrymander.”

In Wisconsin’s 2012 Assembly races, for example, where Democratic candidates received 200,000 more votes overall than Republicans — 1.4 million versus 1.2 million — Republicans managed to overwhelmingly capture the Assembly, 60 seats to 39.

State Republicans drew the boundaries in 2011, insisting it was the GOP’s right and duty after winning control of state government. Democrat litigants insist Republicans unconstitutionally gerrymandered the lines to benefit the GOP.

Today’s federal court ruling can be appealed to the U.S. Supreme Court.