In general, the mantra of “If you can see it you can shoot it” will keep you safe from legal prosecution in the United States, but not all countries and states are the same so check out local laws before shooting.
And he mentions and I would add: So long as you are not standing on private property that is posted no trespassing or if you have been informed that you are on private property and have been asked to leave because you do not have explicit permission to be on that property.
In my experience it’s nice prose, the First Amendment, but in practice guys and gals in any kind of uniform tend to take themselves quite seriously. I’ve never been asked to leave private, or in two cases, public property. I have been ordered to leave, never asked.
Thorin mentions and I have had words with a security guard over exactly this topic. The security guard, the property owner and even the police cannot confiscate your camera, film or digital media card without a warrant.
It’s a good and important read for photographers that like to roam the streets. And, no, Mr. Kiosowski makes it clear and now it’s my turn, neither of us are lawyers. If you have legal questions or issues a real lawyer seems like the proper place for a consultation.