A law that drew massive protests and made Wisconsin the center of a national fight over union rights is back in court on Tuesday, facing a new challenge from teachers and public workers brought after the state’s Supreme Court flipped to liberal control.

The 2011 law, known as Act 10, imposed a near-total ban on collective bargaining for most public employees. It has withstood numerous legal challenges and was the signature legislative achievement of former Republican Gov. Scott Walker, who used it to mount a presidential run.

The law catapulted Walker onto the national stage, sparked an unsuccessful recall campaign, and laid the groundwork for his failed 2016 presidential bid. It also led to a dramatic decrease in union membership across the state.

If the latest lawsuit succeeds, all public sector workers who lost their collective bargaining power would have it restored. They would be treated the same as the police, firefighter and other public safety unions who remain exempt.

The law is “fundamentally unequal,” irrational and unconstitutional, unions argue in court filings.