Berkeley, Calif. — A union representing 8,500 service workers on University of California campuses began a five-day strike today, defying a judge’s temporary restraining order that sought to prevent them from walking off their jobs.

The union, which is affiliated with the American Federation of State, County, and Municipal Employees, known as AFSCME, represents bus drivers, cooks, custodians, and other service workers on all 10 campuses of the university system. The union and the system have failed for nearly a year to reach an agreement over wage increases.

Last month several prominent Democratic politicians canceled scheduled appearances as commencement speakers on the campuses to show their support for the workers. The speakers included former President Bill Clinton, a retired U.S. Army general, Wesley K. Clark, and two members of Congress.

On Friday a San Francisco judge ordered the union not to strike until a hearing next week, saying it had not given the university adequate notice of the planned job action. But the union, which has rejected university offers to increase wages from $10.28 an hour to $11.50 or $12 an hour, ignored the order. The strike coincides with a meeting of the university’s Board of Regents, to be held this week in Santa Barbara, Calif.

“It’s our right to strike,” Lakesha Harisson, president of the state chapter of AFSCME, told the Daily Bruin, the student newspaper on the Los Angeles campus. “It’s illegal for them to prevent people from exercising their constitutional right.” —Josh Keller