The issue concerns something that deeply divided the court in 2016: whether non-members of public sector unions can be required to pay so-called "fair share" fees germane to collective bargaining.
The case is brought by Mark Janus, an Illinois public sector employee, who says the fees violate his First Amendment rights. Court precedent holds that while a non-member does not have to pay fees that go to political activities, that exemption does not include fees for issues such as employment conditions and employee grievances.
Unions fear the court might overrule that precedent which would be a big blow to their coffers at a time when union membership is already on a decline.
The high court voted to take up a similar case back when Justice Antonin Scalia
was still alive, but he died before the case was decided. The justices ended up splitting 4-4 on the issue automatically affirming the lower court's opinion that went in favor of the unions.
AFSCME President Lee Saunders urged the court not to go back on past rulings.
"This case is yet another example of corporate interests using their power and influence to launch a political attack on working people and rig the rules of the economy in their own favor," Saunders said in a statement Thursday. "The merits of the case, and 40 years of Supreme Court precedent and sound law, are on our side. We look forward to the Supreme Court honoring its earlier rulings."
Claire Prestel, a lawyer for the Services Employees International Union, feared impact of the court ruling in favor of Janus.
"If you get all the services for free, it gets a lot harder to convince anyone to become a member, which is why we don't have that system in the first place," she said earlier in the month at an event sponsored by the American Constitution Society.
Lawyers for the National Right to Work Legal Defense Foundation and the Liberty Justice Center are representing Janus and they praised the court's decision to step in.
"We are pleased the Supreme Court has agreed to take up this case and revisit a 40-year-old precedent that has allowed governments to violate the First Amendment rights of millions of workers," said Liberty Justice Center's Jacob Huebert in a statement.
"People shouldn't be forced to surrender their First Amendment right to decide for themselves what organizations they support just because they decide to work for the state, their local government or a public school," he added.
In all, the justices took up nine new cases for a term set to begin on October 2.