The Switchmen's Union of North America v. National Mediation Board case in 1943 revolved around the interpretation and application of certain provisions under the Railway Labor Act. The Switchmen’s Union challenged the National Mediation Board's decision to hold a representation election among employees, arguing that it violated their rights as they had not requested such an action. However, the Supreme Court ruled against them, stating that under Section 2 Ninth of the Railway Labor Act, it was within the power and discretion of the National Mediation Board to investigate disputes concerning representation matters even without a formal request from any party involved. This ruling affirmed that unions do not have exclusive control over initiating changes in employee representation; rather this authority lies with federal agencies like NMB who are tasked with ensuring fair labor practices.

In the dissenting opinion for Switchmen's Union of North America v. National Mediation Board, Justice Frank Murphy argued that the majority had misinterpreted the Railway Labor Act and overstepped its judicial authority by intervening in a labor dispute that should have been left to administrative agencies. He contended that Congress intended for such disputes to be resolved through negotiation and mediation rather than litigation, as evidenced by its creation of the National Mediation Board specifically for this purpose. Furthermore, he believed that courts should defer to these agencies' expertise unless their decisions are clearly unreasonable or unlawful. In his view, neither was true in this case; instead, he saw it as an instance where two unions were competing for representation rights and one was unhappy with how votes were counted - a matter best left to those with specialized knowledge of labor relations.