In the case of National Labor Relations Board v. Reliance Fuel Oil Corp., the U.S Supreme Court ruled in favor of the National Labor Relations Board (NLRB). The dispute arose when an employee was dismissed from his job at Reliance Fuel Oil Corporation for testifying before a congressional committee about labor conditions within the company. The NLRB argued that this dismissal violated Section 7 of the National Labor Relations Act, which protects employees' rights to engage in concerted activities for mutual aid or protection. In contrast, Reliance contended that because it did not interfere with any union activity and there were no ongoing labor disputes at their firm, they had not violated any laws by firing him. The Supreme Court sided with NLRB's interpretation of Section 7 as protecting more than just union-related activities but also other actions taken by employees to improve working conditions collectively. Therefore, dismissing an employee who testified before Congress about such matters constituted unfair labor practices under federal law.

In the dissenting opinion for the National Labor Relations Board v. Reliance Fuel Oil Corp., Justice Harlan disagreed with the majority's interpretation of Section 8(a)(3) of the National Labor Relations Act, which prohibits employers from discriminating against employees in order to discourage union membership. He argued that this section should not be interpreted as prohibiting all forms of discrimination, but only those specifically intended to discourage union membership. In his view, an employer should have a right to terminate an employee for any reason other than their union affiliation or activities. Therefore, he believed that Reliance Fuel Oil Corp.'s decision to fire its employee was lawful because it was based on reasons unrelated to his involvement in labor unions.