The Supreme Court’s ruling in an Illinois labor case gave Republican Gov. Bruce Rauner a rare victory in his campaign to weaken public-worker unions and something to tout in a tough re-election battle.

It also has fired up unions and their Democratic allies who are looking to stop him.

The court on Wednesday said public employees can’t be forced to pay fees to labor unions that represent them in collective bargaining. The decision is expected to financially weaken unions and affect millions of government workers nationwide.

Rauner, who faces billionaire businessman J.B. Pritzker in November, filed the initial lawsuit challenging the fees shortly after taking office in 2015. He called the decision a “historic victory” for free speech and taxpayers.

Pritzker says he’s “appalled” by the ruling.