Holmes, writing for a unanimous majority, ruled that it was illegal to distribute flyers opposing the draft during World War I. Holmes argued this abridgment of free speech was permissible because it presented a "clear and present danger" to the government's recruitment efforts for the war. Holmes wrote:
The most stringent protection of free speech would not protect a man falsely shouting fire in a theater and causing a panic. [...] The question in every case is whether the words used are used in such circumstances and are of such a nature as to create a clear and present danger that they will bring about the substantive evils that Congress has a right to prevent.
Holmes wrote of falsely shouting fire, because, of course, if there were a fire in a crowded theater, one may rightly indeed shout "Fire!"; one may, depending on the law in operation, even be obliged to. Falsely shouting "Fire!" in a crowded theater, i.e. shouting "Fire!" when one believes there to be no fire in order to cause panic, was interpreted not to be protected by the First Amendment.
