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.

The Bill of Rights
For further material:
The National Lawyers Guild
PDFs available from the NLG Los Angeles Chapter.
More resources available from the Massachusetts Chapter.
Just Cause Law Collective
The Midnight Special Law Collective
Video Activism