US Constitution - Bill of Rights (1st Amendment)

Amendment I

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.

Reference: http://www.archives.gov/exhibits/charters/bill_of_rights_transcript.html