In the case of American Federation of Musicians of the United States and Canada et al. v. Wittstein et al., 1964, the Supreme Court ruled in favor of a group of musicians who were expelled from their union for working with non-union employers. The court held that under Section 101(a)(5) of the Labor-Management Reporting and Disclosure Act (LMRDA), any disciplinary action taken by a labor organization must be preceded by written specific charges, adequate notice, and an opportunity for a fair hearing before an impartial body within such organization. The union had failed to provide these protections to its members prior to expulsion; therefore, it was found guilty on all counts. The ruling underscored that unions cannot arbitrarily expel or discipline their members without due process as outlined in LMRDA - reinforcing workers' rights against potential abuses by labor organizations.

In the dissenting opinion for American Federation of Musicians v. Wittstein, Justice Harlan argued that the majority's decision to allow a union to impose fines on its members who worked during a strike was an overreach of federal labor law. He believed that Congress did not intend for unions to have such power when it passed the Labor Management Relations Act in 1947. Furthermore, he contended that allowing unions this authority could lead them to abuse their power and infringe upon individual rights by imposing excessive or unjust penalties on their members. In his view, disputes between workers and their unions should be resolved through state courts rather than under federal jurisdiction as they involve internal matters related more closely with contract law than labor relations issues.