Muni’s transit workers have preliminarily approved the right for their leadership to call a strike, but the City Attorney’s Office has quickly struck back, saying any work stoppage would be illegal under San Francisco’s charter.

On Friday, the Transport Workers Union Local 250-A, which represents 2,200 Muni operators, approved a measure that would allow President Rafael Cabrera to authorize a strike if current labor negotiations reach an impasse.

The voting won’t be finalized until Thursday, and even then, it wouldn’t assure a strike by the transit operators.

Still, the preliminary vote prompted a statement from City Attorney Dennis Herrera, who said a work stoppage by the operators is strictly prohibited in the union’s contract with the San Francisco Municipal Transportation Agency, which operates Muni.

“If it appears a threatened or actual strike will significantly disrupt public transportation and endanger the public welfare — we will take appropriate legal recourse,” Herrera said. “The terms of the existing MOU [memorandum of understanding] prohibit a strike, and the Charter declares that strikes by City employees are not in the public interest.”

wreisman@sfexaminer.com