In the 1962 case Brotherhood of Locomotive Engineers et al. v. Louisville & Nashville Railroad Co., the Supreme Court dealt with a dispute between a labor union and a railroad company over whether certain work should be performed by firemen or hostlers, two different types of railroad employees. The court ruled in favor of the Brotherhood of Locomotive Engineers (BLE), stating that under their collective bargaining agreement with the Louisville & Nashville Railroad Company, they had exclusive rights to perform tasks traditionally done by locomotive engineers such as operating engines around roundhouses and terminals for minor repairs and servicing purposes. This decision was based on an interpretation of "job protective agreements" which were designed to protect workers from job loss due to technological advancements or changes in operational procedures within industries.

In the dissenting opinion for Brotherhood of Locomotive Engineers et al. v. Louisville & Nashville Railroad Co., Justice Douglas argued that the court majority had overstepped its bounds by interpreting a collective bargaining agreement between private parties, which he believed was not within their jurisdiction. He contended that this case should have been resolved through arbitration as provided in the Railway Labor Act, rather than being decided by courts or administrative agencies like National Mediation Board (NMB). According to him, NMB's role is limited to resolving disputes about who represents employees and it does not extend to interpretation of contracts. Furthermore, he criticized the majority’s reliance on extrinsic evidence such as past practices and negotiations history while ignoring clear contract language favoring engineers' union position regarding firemen staffing requirements on diesel locomotives.