In the case of Elfbrandt v. Russell et al., 1965, the U.S Supreme Court ruled that an Arizona law requiring state employees to take a loyalty oath was unconstitutional. The law required public employees to swear they were not members of the Communist Party or any group advocating for overthrowing the government. A Quaker and conscientious objector working as a public school teacher refused to sign this oath, arguing it violated his First Amendment rights by forcing him into making political statements he did not agree with. The court agreed in a 6-3 decision, stating that while states have legitimate interests in ensuring their employees are loyal, such broad and vague laws could potentially punish innocent associations and beliefs protected under freedom of speech and assembly clauses.

In the dissenting opinion for ELFBRANDT v. RUSSELL et al., Justice White argued that the loyalty oath required by Arizona state law was not overly broad or vague, and did not infringe on First Amendment rights. He contended that it only targeted those who knowingly became members of an organization with a specific intent to overthrow the government through force or violence, which is constitutionally permissible. The justice believed that this requirement would deter potential subversives without punishing innocent association or belief. Furthermore, he disagreed with the majority's interpretation of "knowingly" in relation to membership in such organizations; he asserted it should be read as requiring knowledge of both membership and unlawful objectives rather than just one aspect alone.