(Reuters) - A union that represents public workers in Wisconsin is attempting to use the U.S. Supreme Court's 2018 decision barring compulsory union fees for public employees to its advantage in a renewed challenge to the state's controversial 2011 law limiting public-sector collective bargaining.

On Friday, a three-judge panel of the 7th U.S. Circuit Court of Appeals will weigh an International Union of Operating Engineers (IUOE) local's claims that a pair of prior decisions from the appeals court upholding parts of the Wisconsin law, known as Act 10, should be overruled in light of the Supreme Court decision in Janus v. AFSCME.

Act 10, which spurred statewide protests and an unsuccessful bid to oust former Wisconsin governor Scott Walker, prohibits public employers from bargaining with unions over any issue except base wages and from deducting union dues from workers' paychecks, even when employees consent to them.

The law also made it more difficult for public-sector unions to win elections by treating non-votes of abstaining workers as votes against union representation.

The 7th Circuit in cases decided in 2013 and 2014, and the Wisconsin Supreme Court in 2014, rejected unions' constitutional challenges to those provisions. The courts said Act 10 did not force public workers to engage in speech, nor did it violate their equal protection rights by favoring workers who do not join unions over those who do.

But in Friday's case, IUOE and two of its members say Act 10 infringes on the very rights the Supreme Court in Janus held to be fundamental.

"If the Supreme Court is to be taken at its word and apply the broad First Amendment principles outlined in Janus fairly and uniformly, then Plaintiffs' challenges to Act 10 should be well taken," lawyers from Baum Sigman Auerbach Neuman wrote in the plaintiffs' June brief.

The court in Janus said because collective bargaining with the government is inherently political, requiring public employees who do not join unions to pay so-called agency fees to fund bargaining violated their free-speech rights.

U.S. District Judge J.P. Stadtmueller in Milwaukee disagreed with the IUOE in April and dismissed the case. He said the union was wrong on the merits, citing the prior 7th Circuit rulings, and also lacked standing to challenge Act 10 because the union could not demonstrate it had been injured by the law.

IUOE in its appeal says the law's harm was done to its members, and that it has representational standing to bring the challenge on their behalf.

The state countered in a July brief that unlike the mandatory fees at issue in Janus, Act 10 does not compel speech, since public employees in Wisconsin remain free to vote for union representation, vote against it, or abstain.

"In Janus there was no choice; here, choice is a feature of the challenged law," lawyers from the Wisconsin Attorney General's office wrote.

The Republican-controlled state legislature, which intervened in the case to defend Act 10 and is represented by Troutman Pepper Hamilton Sanders, made similar arguments in a separate brief filed in August.

The state is backed by the National Right to Work Legal Defense Foundation, which said in a July amicus brief that IUOE's reading of Janus was flawed. The high court decision involved the rights of individual workers, the group said, while Act 10 implicates collective bargaining and voting in union elections.

The case is International Union of Operating Engineers Local 139 v. Dale, 7th U.S. Circuit Court of Appeals, No. 20-1672.

For the plaintiffs: Brian Hlavin of Baum Sigman Auerbach Neuman

For the state: Clayton Kawski of the Wisconsin Attorney General's office

For the state legislature: Misha Tseytlin of Troutman Pepper Hamilton Sanders