MADISON, Wis. -

A federal court says voting districts drawn by Wisconsin Republicans are unconstitutional.

Attorney General Brad Schimel said he'll appeal the ruling.

The ruling issued Monday strikes down the lines for 99 Assembly and 33 Senate districts across the state that were re-drawn by the GOP in 2011. A dozen voters sued last year, arguing that the boundaries discriminated against Democrats by diluting their voting power.

"We find that Act 43 was intended to burden the representational rights of Democratic voters," wrote the two judges in the majority, Judge Barbara Crabb and Judge Kenneth Ripple. "We find that the discriminatory effect is not explained by the political geography of Wisconsin nor is it justified by a legitimate state interest."

The decision is a major victory for Democrats who have been in the minority for six years and lost ground in this year's election.

"We've known for years that Republican politicians have abused their power to rig Wisconsin elections in their favor," Senate Minority Leader Jennifer Shilling, D-La Crosse, said. "Every voter deserves to have their voice heard and I am relieved that our judicial system is helping to hold Republicans accountable for their unconstitutional partisan power grabs."

Attorneys for the state argued that the districts reflect that Wisconsin has been trending Republican.

Judge William Griesbach dissented in the case, saying the U.S. Supreme Court would disagree with the lower court ruling, and also said the other judges had decided the case on an incorrect standard.

"I am unable to accept proof of intent to act for political purposes as a significant part of any test for whether a task constitutionally entrusted to the political branches of government is unconstitutional," Griesbach said. "If political motivation is improper, then the task of redistricting should be constitutionally assigned to some other body, a change in law we lack any authority to effect."

Attorney General Brad Schimel said in a statement Monday that he intended to appeal the ruling to the U.S. Supreme Court.

“This 2-1 decision does not affect the results of this month’s election or any prior election and legislative district boundaries remain unchanged until the court rules on any remedy," Schimel said.

Many state Republicans were deferring questions to the Wisconsin Department of Justice.

But Assembly Speaker Robin Vos issued a statement late Monday.

“There are only two things that are certain about this case: it’s unprecedented and it isn’t over," Vos said.