First Amendment

The First Amendment to the United States Constitution codifies the freedom of speech as a constitutional right. The Amendment was adopted on December 15, 1791. The Amendment states:

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.

Freedom of speech in the United States

http://en.wikipedia.org/wiki/Freedom_of_speech_in_the_United_States