It is my understanding that events open the public (to say nothing of public spaces) are open to photographers--whatever military thugs, cops, etc. may say. If you use the photographs for commercial purposes, of course, without a release from those photographed, you may be in trouble. For news purposes, however, I believe the First Amendment applies--if there's no expectation of privacy.

However, I haven't researched the law. Does anyone have a different understanding?