Actually it is the law at every trade show I've ever exhibited at, just about to the point where you can't plug in anything without a union electrician doing it. One can usually get away with plugging in a laptop, but certainly if you need anything more than the single standard 10A 2-outlet power drop, expect to pay and wait for the official electrician (and they will kick you out of the show for violations).
Edit: I've seen this at least in NY, Florida, California
Edit: I've seen this at least in NY, Florida, California