The case Booster Lodge No. 405, International Association of Machinists & Aerospace Workers, AFL-CIO v. National Labor Relations Board et al., in 1972 revolved around the issue of whether a union could enforce fines against its members for crossing picket lines during a strike that was deemed illegal by the National Labor Relations Board (NLRB). The Supreme Court ruled in favor of the NLRB and held that unions cannot fine their members for working during an unlawful strike because it would undermine federal labor policy which aims to protect employees' rights to refrain from participating in such strikes. This decision upheld the power and authority of NLRB rulings on labor disputes while also reinforcing workers' rights under federal law.

In the dissenting opinion for Booster Lodge No. 405, International Association of Machinists & Aerospace Workers, AFL-CIO v. National Labor Relations Board et al., Justice William O. Douglas argued that the majority's decision was a departure from established labor law principles and an intrusion into union autonomy. He contended that unions should have the freedom to discipline their members without interference from outside bodies like courts or government agencies unless there is clear evidence of harm to individual rights or public interest. In this case, he believed no such harm existed as it involved internal disciplinary action against a member who crossed picket lines during a strike - an act generally considered disloyal in union contexts. Furthermore, he criticized the majority's reliance on legislative history rather than statutory language in interpreting Section 8(b)(1)(A) of the National Labor Relations Act (NLRA). According to him, nothing in NLRA suggests Congress intended to limit unions' ability to enforce loyalty among its members through penalties.