In the 1950 case Garner et al. v. Board of Public Works of Los Angeles et al., the U.S Supreme Court upheld a loyalty oath requirement for public employees in Los Angeles, California. The plaintiffs were city employees who refused to sign an affidavit affirming they had no affiliation with any organization that sought to overthrow the government by force or violence, as required by a municipal ordinance enacted during the Cold War era's "Red Scare". They argued this violated their First Amendment rights and was too vague in its wording. However, the court ruled against them stating that such oaths served as reasonable measures for municipalities to ensure their employees' loyalty and did not infringe upon constitutional protections of free speech or association.

In the dissenting opinion for Garner et al. v. Board of Public Works of Los Angeles et al., Justice Black argued that the loyalty oath required by city employees in Los Angeles was a violation of their First Amendment rights to freedom of speech and association, as well as their Fifth Amendment right against self-incrimination. He contended that such oaths were inherently coercive and served to suppress political dissent rather than protect national security or public order. Furthermore, he expressed concern about the vagueness and broadness of terms like "subversive" or "un-American", which could be arbitrarily interpreted and applied in ways that unfairly targeted certain individuals or groups based on their political beliefs or affiliations. In his view, this kind of ideological screening amounted to an unconstitutional form of thought control incompatible with democratic principles.