I wouldn't quite call it a law, but it's against regulations here to have a lightsaber duel on the quad. Funny story, actually.
There was a thunderstorm going on, and these two guys were just going at it out on top of Rickover Circle. Flips, spins, everything. The duty master-at-arms didn't want them to be injured or anything, so he went out in a golf cart to try to bring them back in. On trying to persuade them to do so, he was told to go do inappropriate things to his mother for trying to keep them from practicing their religion (sure enough, they had Jedi stamped on their ID tags), and they just kept fighting. The MA wasn't happy about this for obvious reasons, and even less happy about having to get out in the rain to attempt to drag them in by force. Long story short, he was hit in the face, fell over, bonked his noggin, and now we can't have nice things.