The key question with free speech is what constitutes "speech" itself. One view separates public or political speech from private speech, holding that the latter may be limited with respect to the rights of others. The Supreme Court has protected certain kinds of speech in certain circumstances but not all kinds of speech. There are two important limitations on freedom of speech: speech cannot threaten the public order or be obscene.
In Schenck v. United States (1919), Justice Oliver Wendell Holmes stated that freedom of speech could be restricted if the speech represented a clear and present danger; the example he gave was that a person could not shout, "Fire!" in a crowded theater that was not on fire. Through the early years of the Cold War, the clear and present danger test was used to limit the free speech of socialists and communists. The Supreme Court upheld the Smith Act (1940) that made it a crime to advocate the overthrow of the government by force. Under Chief Justice Earl Warren, the Court took the position that political speech was protected under the First Amendment unless it incited "imminent lawless action" or was "likely to produce such action."
Nonpolitical public speech may not be to everyone's taste, and the Supreme Court has had to consider laws that restrict it. Some statements are deemed fighting words and are not protected. There have been cases in which a speaker was arrested because what was said might have caused a riot or a harmful disturbance. Regarding public speech, the Court has tended to approve laws that are very narrowly drawn and to reject those that paint limitations on public speech with too broad a brush.
Some forms of speech involve not words but actions, usually as part of a political protest. Examples of symbolic speech include burning the American flag and burning draft cards during the Vietnam War. The Supreme Court has sometimes protected such actions even though people might find them objectionable because they are, in effect, expressions of political ideas. In United States v. Eichman (1990), the Court declared the Flag Protection Act of 1989 unconstitutional on these grounds.