Another clash over public photos

A photographer taking pictures in the public areas at Union Station deleted his photos under pressure from Amtrak employees. More details at the Discarted blog. Apparently it's in violation of Amtrak policy to interfere with photographers, though it seems employees don't know it or don't care. I know there are very few, if any, situations where a security guard or a law enforcement officer has legal standing to confiscate your photos, but I'd love a short, to the point rundown of the legal situation.