The Brotherhood of Locomotive Firemen & Enginemen et al. v. Pinkston case in 1934 revolved around a dispute between the union and an individual worker, Pinkston, who was dismissed from his job as a fireman on the Illinois Central Railroad due to alleged negligence. The union refused to represent him in his appeal against this dismissal because he had not paid dues for several months prior to his discharge. He sued the union for damages claiming that they breached their duty of fair representation by refusing to assist him. The Supreme Court ruled in favor of Pinkston, stating that labor unions have a legal obligation under federal law (the Railway Labor Act) to fairly represent all employees within their bargaining unit regardless if they are members or non-members and irrespective of whether they have paid dues or not. This landmark decision established what is known as "the Duty of Fair Representation", which requires unions representing a collective bargaining unit must equally represent all employees regardless if they are members or non-members.

In the dissenting opinion for the Brotherhood of Locomotive Firemen & Enginemen et al. v. Pinkston case, it was argued that the majority's decision to uphold a lower court ruling in favor of Pinkston, who had been expelled from his union and subsequently lost his job as a result, violated principles of freedom of association and contract rights. The dissent contended that unions should have autonomy over their membership decisions without interference from courts unless there is clear evidence of unlawful activity or abuse of power. It also suggested that allowing individuals to sue unions for expulsion could potentially undermine labor solidarity and disrupt collective bargaining processes by encouraging internal disputes and litigation. Furthermore, it expressed concern about setting a precedent where courts can second-guess or override internal union decisions based on subjective interpretations or biases towards certain types of conduct deemed unacceptable within those specific communities.