In the 1949 case American Communications Association, C.I.O., et al. v. Douds, Regional Director of the National Labor Relations Board, the U.S Supreme Court upheld a provision in the Taft-Hartley Act that required union leaders to swear they were not members of the Communist Party in order to use services provided by The National Labor Relations Board (NLRB). The court ruled 5-1 that this requirement did not violate First Amendment rights as it was within Congress's power to prevent potential disruptions in commerce due to labor disputes influenced by foreign entities such as communist organizations. However, it also stated that if a person had renounced their affiliation with such an organization and could prove so, they should be allowed access to NLRB services without having to sign an affidavit.

In the dissenting opinion for American Communications Assn., C. I. O., et al. v. Douds, Justice Hugo Black argued that the majority's decision to uphold a law requiring labor union leaders to swear they were not members of the Communist Party was unconstitutional and violated First Amendment rights of free speech and assembly as well as Fifth Amendment protections against self-incrimination. He contended that Congress did not have unlimited power to regulate unions under its commerce clause authority, especially when such regulation infringed upon fundamental constitutional liberties like freedom of association and belief. Furthermore, he believed this requirement could potentially lead to further governmental intrusion into private beliefs or affiliations in other areas beyond labor relations.