In the wake of a 2018 Supreme Court ruling that public-sector unions cannot force non-members to pay a fee for workplace representation, a new challenge to union power is taking shape.

The Supreme Court ruled in the case of Janus v. AFSCME that unions could not extract what’s called an “agency fee” from non-members who happened to work in the same place a union had “exclusive representation” rights. But one group argues that in saying it was unconstitutional to force people to fund labor unions’ speech with their own money, the high court also indicated that the legitimacy of “exclusive representation” itself could be up for debate.

"The issue with regard to exclusive representation was not presented to the court in the Janus case, but the court three separate times expressed grave concerns about the constitutionality of those provisions," said Robert Alt, chief executive of the Buckeye Institute, a free-market think tank. He says that the move by Justice Samual Alito in crafting the Janus opinion was an "invitation for litigants" to bring cases challenging exclusive representation.

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“We took that hint and have brought multiple cases in order to raise that question up to the Supreme Court," he told Fox News.

Alt and the Buckeye Institute are representing Jonathan Reisman -- an economics professor at the University of Maine who was for years active as a grievance officer with his local union -- in Reisman v. Associated Faculty of the University of Maine, a case challenging state-mandated exclusive representation schemes as unconstitutional.

Reisman lost his case in the First Circuit Court of Appeals earlier this month, but Alt said his institute intends to file a petition in early January asking the Supreme Court to hear it.

Over time, Reisman grew frustrated by the local union's association with two larger labor organizations whose political speech he didn't embrace: the Maine Education Association and the National Education Association.

While Reisman says in a profile on the Buckeye Institute's website that he was happy the Supreme Court ruled in Janus he would not have to fund union activities, he argues that is not enough. Maine has a law requiring any workplace in which 50 percent of the employees vote to be represented by a union to allow that group “exclusive representation” of all employees in that bargaining unit. This means Reisman cannot negotiate the terms of his employment for himself – the union speaks for him.

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“The union still has the ability to be my exclusive representative,” Reisman said in a video. “And I’m still associated with the positions that they take. That really is the problem.”

As an example, Reisman wrote in an op-ed for The Portland Press Herald in 2018: "Most recently, the NEA issued a ‘social justice’ grant to a now-retired University of Southern Maine professor, which was used to fund a trip to Washington promoted as a protest of the Brett Kavanaugh nomination, in violation of University of Maine System political advocacy and academic policies."

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The Buckeye Institute also represents teachers in two similar cases – a professor in Minnesota and a Spanish teacher in Ohio. Those cases are pending in lower courts.

The AFUM, the MEA and the NEA didn't respond to requests for comment.

It's unclear whether the Supreme Court will take up the Reisman case, let alone whether Reisman will prevail if it does. The top court often allows legal disputes to play out in the lower courts for years before stepping in.

But the case aims to strike a blow to the model of organized labor, since exclusive representation for employees makes a union more powerful than it otherwise might be, even if it's not collecting agency fees from nonmembers.

The New Jersey chapter of AFSCME explained how exclusive representation benefits unions in an FAQ on its website after the Janus ruling.

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"Exclusivity is how we stay out of a race to the bottom. When the union represents everyone in the unit, employers can’t pit worker against worker or union against union," it says. "However, anti-union organizations and some unions that represent few public-sector workers have suggested that ending exclusivity would be a relief to public sector unions. They fail to understand that if non-members can be treated differently from members the employer could give non-members a better deal in the short run to entice members out of the union."

The First Circuit, for its part, ruled earlier this month that exclusive representation does not violate public-sector workers' First Amendment rights because the union is the designated agent for the bargaining unit as a whole rather than each individual.

"Exclusive bargaining representation by a democratically selected union does not, without more, violate the right of free association on the part of dissenting non-union members of the bargaining unit," the court said, quoting itself in a different case from 2016.

It really turns on this issue of is it permissible … for a state by state law to appoint a group to functionally lobby on behalf of an individual against their will? ... There's no way that is permissible under the First Amendment — Robert Alt, Buckeye Institute

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The Buckeye Institute is not the only group testing the legal limits of Janus. A class-action suit filed in Illinois federal court earlier this year seeks to retroactively apply the ruling to force unions to pay back the dues it collected from non-members without their consent.

Alt says these and other cases that involve compelled speech have a strong chance of succeeding with the current composition of the Supreme Court.

"The Supreme Court has taken a renewed interest in the question of compelled speech," he told Fox News. "It really turns on this issue of, is it permissible … for a state by state law to appoint a group to functionally lobby on behalf of an individual against their will? And I think the answer to that question is abundantly clear. There’s no way that is permissible under the First Amendment."