Some labor leaders said that Mr. Walker’s measure all but eviscerated many public sector unions, leaving members wondering exactly what bargaining ability they were getting for their dues, which under the law can no longer be automatically withdrawn from their paychecks. Act 10 limited bargaining rights to pay raises within the rate of inflation. And with higher contributions from workers for their health care and pensions under the law, some union members said they could no longer afford dues. One Wisconsin union said it had lost as much as 60 percent of its membership.

“We were preparing our locals for this outcome, and in all honesty, we have been moving forward under the assumption that it would be this way,” said Kim Kohlhaas, the president of AFT-Wisconsin.

With the legal challenges over, at least for now, union leaders and Democrats, who hold minorities in both of the state’s legislative chambers, said they would still pursue changes through the coming elections.

Act 10 proved divisive in the state, which decades ago became the nation’s first to give public sector unions the ability to negotiate contracts. The changes led to recall efforts against Mr. Walker and legislators in 2011 and 2012, and remain an issue in Mr. Walker’s re-election campaign this year.

“It’s been a sobering time, but we carry on and people are ready to make it right,” said Boyd McCamish, executive director of District Council 48 of the American Federation of State, County and Municipal Employees, in Milwaukee.

Mr. Walker’s opponent this fall, Mary Burke, a Democrat and former business executive, has said she favors collective bargaining. Polls have shown the race is close. “Mary supports the right of workers to collectively bargain, and believes that the concessions on health care and pension were fair, but should have been reached through the collective bargaining process,” a statement from Ms. Burke’s spokesman, Joe Zepecki, read in part.

In a pair of other rulings, the justices upheld a state law requiring that photo identification be shown at polling places, while also requiring officials to consider waiving the cost of securing documents needed to get such identification. The rulings will have no immediate effect on Wisconsin voters, however, because of a federal court decision in April that the law violates the Constitution. That decision is being reviewed by a federal appeals court in Chicago.

And in the case involving a challenge to a law establishing a domestic partnership registry system for gay couples, the justices said the law did not violate a state constitutional amendment banning same-sex marriage. But a larger question about same-sex marriages in the state is making its way through the federal court system. In June, a federal judge struck down the state’s ban, and that case, along with a similar one from Indiana, is awaiting a hearing in an appeals court.