Collective bargaining allows workers and employers to voluntarily agree on a wide range of issues. Nevertheless, it is limited to some extent by federal and regional laws. A collective agreement cannot be contractual, which is prohibited by law. For example, a union and an employer cannot use collective bargaining to deprive workers of rights they would otherwise enjoy under laws such as the Civil Rights Articles (Alexander v. Gardner-Denver Co., 415 U.P. 36, 94, p. Ct. 1011, 39 L. Ed. 2d 147 [1974]). Nor can collective bargaining be used to waive the rights or obligations that the law imposes on both parties. For example, an employer cannot use collective bargaining to lower the level of safety standards it must meet under the Occupational Safety and Health Act (29 U.S.C.A.

§651 et seq.). 1992] [Remission to NLRB to determine whether salary increases, consisting in terms of date but discretionary in terms of amount, are considered mandatory subjects of negotiation]]. . . .