Clear and present danger

Clear and present danger is a term used in the case Schenck v. United States 249 US 47 1919, a U.S. Supreme Court opinion concerning speech against the draft during World War I:

"Words which, ordinarily and in many places, would be within the freedom of speech protected by the First Amendment may become subject to prohibition when of such a nature and used in such circumstances a to create a clear and present danger that they will bring about the substantive evils which Congress has a right to prevent. The character of every act depends upon the circumstances in which it is done."

See: text and commentary (http://faculty-web.at.nwu.edu/commstud/freespeech/cont/cases/schenck/schenckframe.html)