More than four decades after the Supreme Court ruled that public sector workers could be required to pay dues to unions even if they do not join one, a 5–4 majority on the high court overturned that precedent in a closely watched case that could have major ramifications for the future of public sector unions.

"Under Illinois law, public employees are forced to subsi­dize a union, even if they choose not to join and strongly object to the positions the union takes in collective bar­gaining and related activities," Justice Samuel Alito wrote in the majority opinion. "We conclude that this arrangement violates the free speech rights of nonmem­bers by compelling them to subsidize private speech on matters of substantial public concern."

In the short-term, the ruling in Janus v. American Federation of State, County and Municipal Employees means that plaintiff Mark Janus was successful in his decade-long fight to prevent the union from taking $50 out of his paycheck every two weeks. Over the years, Janus estimates, he's contributed more than $6,000 to the union.

More broadly, Wednesday's ruling could end the automatic deduction of union dues from millions of public employees' paychecks, forcing unions like AFSCME to convince workers to voluntarily contribute dues—something workers would do, presumably, only if they have a reason to do so.

"So many of us have been forced to pay for political speech and policy positions with which we disagree, just so we can keep our jobs. This is a victory for all of us," said Janus in a statement. "The right to say 'no' to a union is just as important as the right to say 'yes.' Finally our rights have been restored."

The ruling is "a landmark victory for rights of public-sector employees," said Mark Mix, president of the National Right to Work Legal Defense Foundation, which supported Janus' lawsuit.

While today's ruling certainly shifts the balance towards worker freedom, groups like the National Right to Work Legal Defense Foundation, which represented Janus, say they are already prepared for additional rounds of litigation. In states that previously have embraced right-to-work policies, unions have often tried to make it as difficult as possible for workers to renounce their membership.

In speaking about his case, Janus has often framed the debate as one of free speech. His interest in not paying union dues was not an attempt to secure "a better deal" on his own outside the union model, he told Reason's Nick Gillespie in June. Rather, he said, "the question is my First Amendment rights to speech and freedom of association."

That was a major point of contention during oral arguments in May. As Reason's Damon Root noted at the time: "The union's position, [Justice Anthony] Kennedy told [Illinois Solicitor General David] Frederick, involved 'mandat[ing] people that object to certain union policies to pay for the implementation of those policies against their First Amendment interests.' In other words, Kennedy seemed to suggest the mandatory fees at issue here are unconstitutional."

The free speech question has divided libertarians, though. Eugene Volokh, editor of the Volokh Conspiracy blog (which is hosted by Reason.com), submitted an amicus brief to the Supreme Court arguing against the First Amendment angle to the Janus case.

Janus is the second case in recent Supreme Court history to wrestle with the underlying question of whether unions can compel the payment of dues from non-members. During 2016, the Supreme Court heard the Friedrichs v. California Teachers Association case, which similarly sought to free non-union members from paying union dues. That case ended in a 4–4 draw after Justice Antonin Scalia's sudden death left the Court with an even number of conservative and liberal members.

Justice Neil Gorsuch, appointed to the court last year to fill Scalia's spot, sided with the majority in Janus.

The Janus case, like Friedrichs before it, was aimed at overturning the 1977 Supreme Court ruling in Abood v. Detroit Board of Education, which upheld mandatory union fees.

In the majority opinion, Alito noted the importance of following precedent "unless there are strong reasons for not doing so."

"But there are very strong reasons in this case. Fundamental free speech rights are at stake," he wrote. "Abood was poorly reasoned. It has led to practical problems and abuse. It is inconsistent with other First Amendment cases and has been undermined by more recent decisions. Developments since Abood was handed down have shed new light on the issue of agency fees, and no reliance interests on the part of public-sector unions are sufficient to justify the perpetuation of the free speech violations that Abood has countenanced for the past 41 years."

Unions had argued that overturning Abood would leave them with non-dues-paying members who would essentially become "free riders" benefitting from collective bargaining activities without contributing towards the associated costs. In a dissenting opinion, Justice Elena Kagan said the free-rider issue would be "a collective action problem of nightmarish proportions" for unions.

Whether you consider them free riders or not, unions are probably right to be worried about losing dues-paying members in the aftermath of the Janus ruling. An analysis by the Illinois Economic Policy Institute, a union-backed think tank, estimates that 726,000 workers nationally would stop paying dues if they had that choice. The loss of union members and their dues could be particularly challenging in blue states, according to the IEPI report. Public sector union membership would decrease by an estimated 189,000 members in California, 136,000 members in New York, and 49,000 members in Illinois.

"The response to Janus will be critical to the long-run survival of the U.S. labor movement," the report warns.

"In the short run, the Janus decision may hurt some unions financially, but in the long run it will serve to make unions and their members more militant and force a stronger culture of internal organizing," said Paul Shearon, secretary-treasurer for the International Federation of Professional and Technical Engineers, in a statement to Reason.

Whether that's true remains to be seen, but certainly Wednesday's ruling ushers in a new era of union politics and shifts power back to individual workers to decide whether unions thrive or fail.

Read more Reason coverage of the Janus case.

John Stossel on the potential to extend "right to work" to public sector employees.

Damon Root on the First Amendment aspects of the case.

Scott Shackford on the Trump administration's Department of Justice reversing its stance on mandatory union dues.

Eugene Volokh and Alicia Hickok debating the merits of the case.

And check out a conversation between Nick Gillespie and Mark Janus on the Reason Podcast.