The government justified this censorship by arresting Charles Schenck under the Espionage Act of 1917 which outlawed acts seen as disloyal to the United States.
Schenck was arrested for distributing flyers that urged men of age to resist the draft. He asserted that he had the right to distribute these flyers due to free speech. The US Supreme Court found that he was unable to legally distribute these flyers in the midst of WWI because draft resistance was seen as a danger to national security. Justice Oliver W. Holmes famously argued and compared Schenck's actions to "falsely shouting fire in a theatre and causing a panic".