Rejecting claims by 24,000 AIDS patients, the California Supreme Court ruled Monday that pharmaceutical giant Gilead Sciences acted legally by marketing a drug for years that was effective but had potentially harmful side effects, while withholding another product that was equally effective but less harmful. “A manufacturer cannot be held liable for injuries caused by a nondefective product,” Justice Joshua Groban said in a 6-1 decision overturning a lower-court ruling that had allowed the patients to sue the Foster City-based company.