In Cox v. Louisiana, the U.S. Supreme Court ruled in 1964 that a state cannot employ "breach of peace" statutes against protesters engaging in peaceful demonstrations that may potentially incite violence. The case arose when Reverend B. Elton Cox was convicted under Louisiana's breach-of-peace law for leading a civil rights protest outside a segregated courthouse which led to his arrest and conviction by local authorities for picketing “near” a courthouse with intent to obstruct justice, disturbing the peace, and obstructing public passages. In its decision, the court held that these laws were too vague and broad thus violating due process as guaranteed by the Fourteenth Amendment because they could be used arbitrarily to suppress free speech rights protected under First Amendment.

In the dissenting opinion for Cox v. Louisiana, Justice John Marshall Harlan II argued that the majority's decision to overturn Cox's conviction was incorrect because it failed to consider the context of his actions. He contended that while freedom of speech is a fundamental right, it does not grant individuals unlimited license to incite violence or disrupt public order. In this case, he believed that Cox had crossed this line by leading a large and potentially volatile crowd in protest against racial segregation near a courthouse where related legal proceedings were taking place. According to Justice Harlan, such conduct could reasonably be seen as posing an imminent threat to peace and safety; therefore, punishing it did not violate the First Amendment. Furthermore, he criticized the majority for second-guessing state courts' interpretations of their own laws without sufficient justification.