The U.S. Supreme Court is considering yet another case involving the Americans with Disabilities Act that could have employers on the defensive. The justices have heard arguments in the case of an oil refinery worker who sued his bosses after they excluded him from work they felt might pose a health risk. Mario Echazabal brought the action against a Chevron plant in El Segundo, Calif., when he was denied an assignment in an area of the plant where chemicals could have aggravated his liver ailment. Echazabal’s lawyers argue that ADA allows only the worker to make that decision, not the employer. Echazabal’s case is the latest in a rash of suits attempting to test the limits of ADA. In five cases involving the workplace, the court has sided with the employer each time. In oral arguments, Justice Anthony Kennedy said the court wants employers to act in the best interests of employees, and that the plaintiff was asking the court to take a position that “is completely barbarous.”