In the 1960 case Travis v. United States, the Supreme Court ruled on a matter involving federal obscenity laws. The defendant, Travis, was convicted under a federal statute for mailing obscene material - specifically, advertisements for nudist magazines and photographs. On appeal to the Supreme Court, Travis argued that his First Amendment rights were violated by this conviction because he believed that nudity itself could not be classified as obscene. However, in its decision against him (affirming his conviction), the court held that it is within Congress's power to determine what constitutes obscenity and thus regulate it through law enforcement measures such as postal regulations. This ruling reinforced previous decisions upholding Congressional authority over matters of public morality and decency standards.

In the dissenting opinion for Travis v. United States, Justice Brennan argued that the Smith Act, which made it a crime to advocate or teach the duty of overthrowing the government by force or violence, was unconstitutional as applied in this case. He believed that there was insufficient evidence to prove that defendants had advocated for immediate violent action against the government rather than simply expressing their belief in Marxist-Leninist theory and its eventual triumph over capitalism. The majority's interpretation of "advocacy" under this law threatened First Amendment rights because it could potentially criminalize mere expression of ideas without any intent or likelihood of inciting imminent lawless action. Furthermore, he criticized how jury instructions conflated advocacy with conspiracy and failed to clarify what constituted illegal advocacy versus protected speech about abstract doctrine.