Criticizing the government
During World War I, Americans opinion differed on whether it was good or not for the U.S. to be involved in the war at all, or to be part on the side of the Allies. The government, being aware of this internal dissent, decided to put an halt of it, as it considered that criticizing the government during times of war disloyal, unpatriotic and contrary to the war effort, and resolved to enact the Espionage Act (1917) and the Sedition Act (1918), which was an extension to the first.
Both Acts created a lot of controversies because they imposed significant limitations of freedom of speech and freedom of the press, often considered as a violation of the First Amendment.