In Cox v. Louisiana, the U.S Supreme Court ruled in 1964 that a state cannot employ "breach of peace" statutes against public demonstrations to suppress freedom of speech and assembly as protected by the First Amendment. The case arose when Reverend B. Elton Cox was convicted under Louisiana's breach-of-peace law for leading a peaceful protest outside a segregated courthouse lunch counter in Baton Rouge, where he encouraged black students to sit at the whites-only area. The court held that his conviction violated his constitutional rights because it was based on racial discrimination rather than any actual threat or occurrence of violence or disorderly conduct during the demonstration. Furthermore, they found that there were no clear standards defining what constituted a breach of peace which could lead to arbitrary enforcement infringing upon free speech rights.

In the dissenting opinion for Cox v. Louisiana, Justice John Marshall Harlan II argued that the majority's decision was inconsistent with previous rulings on First Amendment rights and public demonstrations. He believed that while freedom of speech is a fundamental right, it does not grant unlimited privileges to individuals or groups to express their views in any manner they choose without considering potential consequences such as inciting violence or causing public disorder. Harlan felt that local authorities should have discretion in managing protests to maintain peace and order, especially when there are concerns about possible violent reactions from counter-protesters or bystanders. He also disagreed with the majority's interpretation of "breach of peace" laws, arguing these laws were designed precisely for situations like this where there is a risk of civil unrest due to provocative speeches or actions by protesters.