A ruling handed down by California’s Supreme Court represents a loss for workers compensation payers’ ability to pursue subrogation claims against certain third parties responsible for an employee’s injuries. Ruling in Seabright Insurance Co. vs. US Airways Inc., the court said Monday that an insurer cannot sue a third-party company when the hiring company fails to follow safety regulations and an injury results. The case involved an employee of Lloyd W. Aubry Co., which US Airways hired to maintain a luggage conveyor at San Francisco International Airport.