If you're standing in a public place, you can shoot whatever you want (barring setting up any "obstacles" (tripods, lighting, etc.) that may restrict traffic flow. (as was the excuse I was given for setting up a tripod - as far as mounting a clamp to the railing...guess they figured I was going to damage the hardened steel chain link whatever with my rubber-coated clamp teeth). As I understand it - this is the law...you can shoot people, places, buildings, etc. - you don't get into "trouble" until you publish or make publicly available images of proprietary nature (shots of people who are not in the "public eye", etc. How the laws are written and how the laws are enforced are two entirely different things - walk along the sidewalk with a huge lens outside of the White House, and you'll probably be stopped and questioned - but you are fully within your rights - then pull a Rodney King! (Double check my statements - This is the law as I've heard it from people I trust, but not actually researched)