Confused?

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.

Protestors were charged with unlawful assembly.

Now I have no understanding of the issues at Gallaudet, but I do wonder how a law can be constitutional when it is for unlawful assembly. Does it have to do with it being private property?