SAN FRANCISCO — Citing the potential for “preclusion, collusion, and exclusion,” U.S. District Judge William Alsup has thrown the brakes on a hard-fought wage-and-hour case because class counsel represent another group of workers against the same company in state court.

“When there are different plaintiffs in different actions proceeding at the same time with the same claims, same counsel, and same defendants, the risk of counsel compromising one class for another is intensified,” Alsup wrote, denying class certification in Lou v. Ma Laboratories on Wednesday. “Counsel have a conflict and may not serve.”