A Wisconsin circuit court judge has invalidated a controversial law designed to limit the power of public-sector unions in the state – legislation that prompted massive protests in Madison, the state capital and brought international attention to Wisconsin earlier this year.

The judge’s 33-page decision, issued Thursday, said that Republican lawmakers violated the state’s open-meeting law in their effort to push through the legislation March 9.

Dane County Circuit Court Judge Maryann Sumi stressed that her decision was based on the evidence of key procedural errors made during the bill’s passage. Those errors, she said, included failing to leave every door of the statehouse open and to provide 24-hour notice that the Legislature was in open session.

“Two days of testimony, numerous exhibits and multiple briefs have revealed nothing that would support a finding that a conflicting legislative rule was in effect at the time,” she wrote.

Wisconsin Republicans now have the options of either taking a new vote on the legislation or pushing the matter to the state Supreme Court to argue, among other things, about whether Judge Sumi operated within her judicial powers.

“There’s still a much larger separation-of-powers issue: whether one Madison judge can stand in the way of the other two democratically elected branches of government. The Supreme Court is going to have the ultimate ruling,” Senate majority leader Scott Fitzgerald (R) wrote in a statement.

The state Supreme Court is already scheduled to hear the case June 6.

As written, the legislation strips away the collective bargaining power of non-law-enforcement public workers on everything except wages. It also increases pension and health-benefit obligations. Moreover, it forces non-law-enforcement unions to hold annual elections to remain certified, and workers will no longer enjoy the ability to deduct union dues from state paychecks.

Going forward, Republicans could choose to roll the collective bargaining language into a larger state budget bill, which is scheduled for a vote in June. However, that strategy brings political risks: A recall election to remove six Republicans from office takes place the following month, on July 12. Three Democrats are also vulnerable.

“Some state senators who were involved in passing the legislation have to be wondering whether or not taking action in June is the right thing or wrong thing politically, a month before facing voters,” says Barry Burden, who teaches political science at the University of Wisconsin in Madison.

On Thursday, State and local union officials said they were pleased with Sumi’s decision but were wary of claiming it represented a complete victory.

“I’m happy in one regard, but [state Republicans] still have the majority in both houses and are bent on changing how we treat public employees in the state,” says Mike Lipp, president of Madison Teachers Inc., which has 3,600 members. “Right now they feel they have all the cards in their hands, and that’s the way they act. They’re going to push until they have it in their favor.”

For their part, Republicans have contended their March 9 meeting operated outside the open-meeting law because the Legislature was in special session, exempting it from Senate rules. They were able to vote on the bill once it was stripped of appropriations, which had prevented it from passing with a simple majority.

Opponents argue that the open-meeting law still applied, because the special committee formed to vote on the bill was made up of members from both the Assembly and Senate.