In the United States v. Thompson case of 1919, the Supreme Court ruled on a matter involving mail fraud. The defendant, Mr. Thompson, was accused of using the U.S Postal Service to defraud individuals by selling them fraudulent stock in his company under false pretenses and promises of high returns that were never fulfilled. He appealed his conviction from a lower court arguing that he had not committed any crime as there was no actual property taken or transferred through mail fraud schemes according to existing laws at that time. However, the Supreme Court disagreed with this argument and upheld his conviction stating that money could be considered property under these circumstances and thus its fraudulent acquisition via postal service constituted mail fraud as per federal law.

In the dissenting opinion for United States v. Thompson, Justice Louis Brandeis argued that the majority's decision to uphold a conviction under the Espionage Act of 1917 was an infringement on free speech rights protected by the First Amendment. He contended that there was no clear and present danger posed by Thompson’s actions - distributing leaflets criticizing American involvement in World War I - which would justify such a restriction on his freedom of expression. Furthermore, he emphasized that it is essential for citizens to be able to criticize their government without fear of punishment, particularly during times of war when emotions run high and decisions can have far-reaching consequences. In essence, Justice Brandeis believed this case represented an overreach by federal authorities into areas constitutionally reserved for individual liberties.