The Cameron et al. v. Johnson, Governor of Mississippi, et al., 1964 case was a significant U.S Supreme Court ruling that upheld the constitutionality of a Mississippi anti-picketing law. The plaintiffs were civil rights activists who had been arrested for picketing in violation of this law and argued that it infringed upon their First Amendment rights to free speech and assembly. However, the court ruled against them on grounds that states have the right to regulate conduct such as picketing if it threatens public order or obstructs access to premises - even if such conduct is expressive in nature and thus potentially protected by the First Amendment. This decision underscored how concerns about maintaining public order can sometimes override individual liberties.

In the dissenting opinion for Cameron et al. v. Johnson, Governor of Mississippi, et al., Justice William O. Douglas argued that the anti-picketing law in question was unconstitutional because it violated First Amendment rights to free speech and assembly. He contended that peaceful picketing is a form of expression protected by the Constitution, regardless of whether its message is popular or not. Furthermore, he criticized the majority's reliance on local authorities' interpretation of "breach of peace," arguing this could easily be manipulated to suppress unpopular views or minority voices under vague definitions and subjective judgment calls about what constitutes a disturbance or threat to public order.