The U.S. Supreme Court case National Labor Relations Board v. Allis-Chalmers Manufacturing Co., et al., 1966, revolved around the issue of whether a union's enforcement of a shop rule that required its members to refrain from doing 'struck work' was protected by federal labor law or constituted an unfair labor practice under Section 8(b)(1)(A) of the National Labor Relations Act (NLRA). The court ruled in favor of the union, holding that such conduct did not violate NLRA as it fell within the realm of legitimate union activities aimed at achieving collective bargaining objectives. The majority opinion emphasized that unions have wide latitude in their internal affairs and can enforce rules against their own members who cross picket lines during strikes without violating federal labor laws.

In the dissenting opinion for the National Labor Relations Board v. Allis-Chalmers Manufacturing Co., Justice Black argued that the majority's decision was an overreach of federal power, infringing on state rights to regulate their own labor disputes. He contended that Congress did not intend for the National Labor Relations Act (NLRA) to cover all forms of employee misconduct and believed it should be limited only to those activities directly affecting commerce or disrupting labor peace. Furthermore, he expressed concern about potential misuse of this broad interpretation by employers seeking protection from any form of worker protest under NLRA provisions. In his view, such a wide-ranging application could potentially undermine workers' right to strike and other collective bargaining tools essential in maintaining balance between employer-employee relations.