Unilateral amendments During the period during which a collective agreement is in force, the employer may not change a condition of employment that is subject to mandatory negotiations without first negotiating with the union (29 U.S.C.A. § 158[d]). Even after the collective agreement expires, the employer must maintain the status quo and must not unilaterally alter the issues of mandatory bargaining until the parties reach an impasse (Louisiana Dock Co.c. NLRB, 909 F.2d 281 [7th Cir. 1990]). This prohibition of unilateral amendments continues even if the employer denies that the union is the sole representative (Livingston Pipe & Tube v. NLRB, 987 F.2d 422 [7th Cir. 1993]; NLRB v. Parents & Friends of the Specialized Living Center, 879 F.2d 1442 [7th Cir. 1989]). Since negotiations in good faith between the parties “exhaust the prospect of reaching an agreement”, the parties have reached an impasse and the implementation of unilateral changes to working conditions does not constitute an unfair labour practice (NLRB v. Plainville Ready Mix Concrete Co., 44 F.3d 1320 [6th Cir. 1995]; United Paperworkers International Union v.
NLRB, 981 F.2d 861 [6th Cir. 1992]; Southwest Forest Industry v. NLRB, 841 F.2d 270 [9th Cir. 1988]). The wage system is an integral part of the collective agreement as it defines the minimum wage. Collective bargaining allows workers and employers to voluntarily agree on a variety of issues. Nevertheless, it is limited to some extent by federal and state laws. A collective agreement cannot contractually achieve what the law prohibits. For example, a union and an employer cannot use collective bargaining to deprive workers of rights they would otherwise enjoy under laws such as civil rights laws (Alexander v. Gardner-Denver Co., 415 U.S. 36, 94 pp.
Ct. 1011, 39 L. Ed. 2d 147 [1974]). Nor can collective bargaining be used to waive the rights or obligations that laws impose 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§§ 651 et seq.). Moreover, the collective agreement is not purely voluntary. .