Justice Holmes created the clear and present danger test in Schenck v. United States (1919), a case in which two members of the Socialist Party—Charles Schenck and Elizabeth Baer—were convicted of violating the Espionage Act of 1917. Schenck and Baer, members of the party’s executive committee, conspired to distribute 15,000 leaflets urging people to resist the draft and avoid service in World War I.

Holmes asked whether the publication would create a “clear and present danger” to the U.S. war effort, the draft, and military recruiting. He noted that many things that may be said in peacetime cannot be said in times of war, concluding that the leaflets constituted a conspiracy to harm the country’s war effort.