"Shouting fire in a crowded theater" is a misquote that refers to Oliver Wendell Holmes, Jr.'s opinion in the United States Supreme Court case Schenck v. United States in 1919 and that is used to express the limits upon which free speech may be expressed under the terms of the First Amendment of the United States Constitution.
Holmes, writing for a unanimous majority, ruled that it was illegal to distribute fliers 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!". 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.
Schenck was later overturned by Brandenburg v. Ohio, which ruled that speech could only be banned when it was directed to and likely to incite imminent lawless action (e.g. a riot), the test which remains until this day.
Some now see the Schenck argument to be mistaken, contending that pamphleteer was more like yelling fire outside a building to prevent people from entering than it was trying to encourage people to stampede out.
Despite Schenck being overturned, the phrase "shouting fire in a crowded theater" has since come to be known as synonymous with an action that the speaker believes goes beyond the rights guaranteed by free speech, reckless or malicious speech, or an action whose outcomes are blatantly obvious.
Jacob Hornberger of the Future of Freedom Foundation, a libertarian think tank, has stated that in most cases, free speech issues in the US depend on whose property one is on at the time. If someone falsely shouted "fire" and created a stampede which was clearly against the wishes or theatre owner's policy of conduct; then the theatre owner would be in his right to prepare charges against the agitator. If, however, the theatre owner decides it would be good for business to have patrons yells "Fire! Fire!" whenever they felt like it, then that is within his right to do so.
