A case scheduled to be heard by the Supreme Court this week has managed to stay out of the limelight, skirting political debate and media frenzy for years despite its potentially devastating ramifications for unions across the country.

Harris v. Quinn is a case started by eight home-care workers who resisted joining a state union — and paying the corresponding union dues — in Illinois. Unionization was a prerequisite for their employment by the state. They filed a class-action lawsuit against Illinois in 2010, arguing that being forced to pay into a union as a condition of their employment violated their First Amendment rights to freedom of association.

As the case worked its way up the court system, with both state and federal appeals courts siding with the state, the lawsuit ballooned from a small class-action case into one that could affect every public-sector union in the country.

If the court rules in favor of the plaintiffs, the foundation of public union funding — the ability to collect compulsory dues — could crumble.

Union leaders and labor supporters are worried that the current Supreme Court, which has had a lukewarm relationship with organized labor, will overturn decades of precedent and find that public-sector unions cannot compel state employees to pay them.

“(The plaintiffs) want to destroy things for working people in the U.S.,” said Keith Kelleher, president of the Service Employees International Union (SEIU) in Illinois. If the court rules in the plaintiffs’ favor, he said, “it would be catastrophic.”

While the Harris v. Quinn case was started by a small group, it has large special interests fighting for it. On one side are big unions who have a vested interest in requiring state employees to pay dues for the union’s non-political activity, as well as the Illinois government and the U.S. federal government, whose representatives believe maintaining their current relationship with unions is mutually beneficial.

On the other side is a medley of groups with conservative ties, most notably the National Right to Work Foundation, which was founded in 1968 to fight against compulsory union dues and other aspects of union membership. While the foundation keeps its donor list private, it has been linked to billionaire conservative mega-donors Charles and David Koch.

The Supreme Court could weigh in on the issue in several ways, with some outcomes more limited than others. But if the court decides to consider the case in its broadest terms, its decision could undermine the bedrock of union funding.

As a bargaining agent for a group of employees, a union is obligated to represent all workers — whether they want to join the union or not. Workers in a unionized sector are therefore not required to join the union, but have to pay dues for costs the union incurs by collectively bargaining on their behalf.