COLUMBUS (AP) – Thousands of union workers, activists, faith leaders and labor supporters are headed to the Ohio Statehouse to draw attention to upcoming arguments in a high-stakes U.S. Supreme Court case.

Organizers say Saturday’s Working People’s Day of Action rally is being observed nationwide.

The lawsuit challenges a 41-year-old ruling that allowed states to require government employees who opt out of union membership to pay their share for activities the union undertakes on behalf of all workers, not just members.

So-called “fair-share fees” cover the costs of collective bargaining and workplace grievance proceedings.

Conservative anti-union interests back the Illinois government employee who says mandating such fees violates his First Amendment speech rights.

The case’s outcome could affect unions representing over 5 million government workers in 24 states and the District of Columbia.