Amendment I (the First Amendment was actually the third amendment in the proposed Bill of Rights, but the first two were not passed by Congress)

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.

Annotations on various legal aspects of the First Amendment: click here for Cornell Law School's Legal Information Institute annotations