Quote Originally Posted by winger
The tripod law in DC might be listed under federal, not DC. When I was in college (several years ago), I went to DC while looking at grad schools. My uncle warned me that I couldn't use a tripod near "the Mall" or any of the monuments. It actually has to do with safety and someone tripping over the legs and also with mistaking one for a weapon. Same rule in Museum of Fine Arts in Boston.
In law enforcement overall, there's more of a sense of "I can't let something happen on my watch." They'd rather err on the side of overcaution than potentially let someone get away with something. Are they right to do it? Maybe, maybe not. But it's absolutely impossible for all the assorted federal, state, and local law enforcement and security guards to strike the right balance that will make everyone happy. The political climate in Massachusetts is a little different from places like TX, but I bet the law enforcement reacts similarly to someone with a tripod at a bridge.
When I was in DC a few years ago, I had no trouble using my camera on a tripod. I tramped all over the monuments and places near them. I didn't make it to the arboretum though. The funniest was when I was on the wide stretch of lawn in front of the white house. I even asked the guards there if it was alright to take a picture, just to be sure. One came over and held my bag for me. Either I'm more intimidating than I think, or I'm so non threatening ( those that know me don't laugh) as to be ignored.

If I had trouble I could have had my son in law step in, he worked for the state dept. at the time. He never had to come to my rescue.