The first amendment to the Constitution of the United States of America: clear.
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.
Basic rule of thumb for filming in public places: straightforward.
Legally, it’s pretty much always okay to take photos in a public place as long as you’re not physically interfering with traffic or police operations. As Bert Krages, an attorney who specializes in photography-related legal problems and wrote Legal Handbook for Photographers, says, “The general rule is that if something is in a public place, you’re entitled to photograph it.” What’s more, though national-security laws are often invoked when quashing photographers, Krages explains that “the Patriot Act does not restrict photography; neither does the Homeland Security Act.”