In Travis v. United States (1966), the Supreme Court ruled that a federal obscenity law was not unconstitutionally vague, upholding the conviction of a man who had mailed obscene material. The defendant argued that the statute under which he was convicted did not provide adequate notice of what conduct it prohibited and thus violated his due process rights. However, the court disagreed, stating that while some aspects of obscenity may be hard to define precisely, this does not make every application of an obscenity statute unconstitutional for vagueness. The court also noted that previous rulings provided sufficient guidance on what constituted obscene material.

In the dissenting opinion for Travis v. United States, Justice Douglas argued that the Smith Act, which criminalizes advocacy of overthrowing the government by force or violence, was being misused to suppress unpopular political beliefs rather than actual threats to national security. He contended that there was no evidence presented in this case showing a clear and present danger posed by those accused under the act. Furthermore, he asserted that their conviction violated their First Amendment rights as it punished them not for any overt acts but merely for expressing certain views and affiliations. Douglas also criticized how guilt was determined based on membership in an organization deemed unlawful without considering whether individuals had specific intent to conspire against the U.S government.