A state judge has ordered graduate student workers at the University of California to temporarily stop their strike at six campuses across the system, delivering a win to UC regents in their legal effort to force strikers back to work.

Both the university system and the academic workers’ union, United Auto Workers Local 4811, said late Friday that the judge in Orange County had granted a temporary restraining order against the work stoppage. UC had argued that the strike would cause “irreparable harm” by disrupting classes and research as finals loom.

The strike began last month in response to the administration’s crackdown on pro-Palestinian protests at the Los Angeles and Irvine campuses, part of a wave of college demonstrations across the country against Israel’s military campaign in Gaza. The union accused the university system of authorizing brutal arrests and violating workers’ right to peaceful protest.

After starting at UC Santa Cruz, the strike spread to five other campuses: UCLA, UC Irvine, UC Davis, UC Santa Barbara and UC San Diego. It now appears to be the largest U.S. work stoppage of the year so far, involving up to 31,500 of the union’s 48,000 members.

The injunction orders graduate student instructors and researchers temporarily back to work while the underlying case moves through a state labor board. The union has accused UC of committing various unfair labor practices stemming from its protest response.

Melissa Matella, UC’s associate vice president for labor relations, said in a statement that the university system was “extremely grateful” for the judge’s order.

“The strike would have caused irreversible setbacks to students’ academic achievements and may have stalled critical research projects in the final quarter,” Matella said.

UC had asked the state labor board twice to seek an injunction and was rebuffed both times. It then took its case to Orange County Superior Court.

Local 4811 cautioned that the judge did not rule the strike to be illegal, as the university system has argued. It also criticized UC regents for going outside of the labor board process in search of a “more favorable outcome” in state court, and vowed to defend the legality of the strike.

The university system has said that the justifications for the strike are purely political and social — rather than work-related — and therefore the stoppage is against the law. But the grad students have maintained that the fight is about their rights as employees to protest without fear of arrest or retaliation.

“UC academic workers are facing down an attack on our whole movement,” Rafael Jaime, the union’s president, said in a statement. “In the courtroom, the law is on our side and we’re prepared to keep defending our rights — and outside, 48,000 workers are ready for a long fight.”

Veena Dubal, a law professor at UC Irvine, said on social media that it was “pretty darn brazen” of the university system to take its injunction request to court after the labor board had twice decline to pursue it.

“UC’s actions are not unlike what Starbucks and Amazon are doing in the private sector: attempting to undermine the bodies governing labor law,” Dubal said.