Al Jazeera: Police arrest hundreds of Occupy LA activists
Huffington Post: Occupy LA Raid: Police Arrest Protesters Who Defied Eviction Notice
The right to freedom of assembly is constitutionally guaranteed in the US — unless it conflicts with local ordinances.
First Amendment: Freedom of Speech, Press, Religion and Petition
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.