In Vaca v. Sipes (1967) 386 U.S. 171, the Supreme Court held that an award of damages against the Union could not include damages attributable solely to the employer's breach of contract. (Id. at p. 196.) "The governing principle, then, is to apportion liability between the employer and the union according to the damage caused by the fault of each. Thus, damages attributable solely to the employer's breach of contract should not be charged to the union, but increases if any in those damages caused by the union's refusal to process the grievance should not be charged to the employer. In this case, even if the Union had breached its duty, all or almost all of plaintiff's damages would still be attributable to his allegedly wrongful discharge by the employer. For these reasons, even if the Union here had properly been found liable for a breach of duty, it is clear that the damage award was improper." (Id. at pp. 197-198.)