Popular Mechanics looks into the legality of taking photos in public places.
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." But this doesn't stop people from interfering with photographers, even in settings that don't seem much like national-security zones.
As security guards everywhere get more and more cagey about public photographs—The Stranger has covered this kind of thing before—it's important to know your rights.