The U.S. Supreme Court case National Labor Relations Board v. Drivers, Chauffeurs, Helpers, Local Union No. 639 involved a dispute over whether the union had violated the National Labor Relations Act by refusing to bargain with an employer about changes in employee wages and working conditions during the term of a collective bargaining agreement. The court ruled that it was not necessary for unions to negotiate every change proposed by employers during the life of an existing contract; however, they were required to discuss significant alterations affecting employees' terms and conditions of employment even if these changes occurred within the duration of a valid agreement. This decision clarified how labor laws applied when contracts were already in place between unions and employers.

In the dissenting opinion for the case National Labor Relations Board v. Drivers, Chauffeurs, Helpers, Local Union No. 639, International Brotherhood of Teamsters, Chauffeurs, Warehousemen and Helpers of America (1959), Justice Frankfurter argued that the majority's decision was a departure from established principles governing labor relations disputes. He believed that it was not within the jurisdiction of courts to interfere in internal union affairs unless there is clear evidence showing violation of federal law or infringement on individual rights protected by statute or Constitution. The justice contended that no such violations were present in this case; rather it involved an intra-union dispute over leadership selection procedures which should have been left to be resolved internally by union members themselves under their own rules and regulations without court interference.