The U.S. Court of Appeals for the 9th Circuit has ruled that it is a federal crime to visit a website after being told not to visit it. This decision is based on the Computer Fraud and Abuse Act.
As the linked article notes, this ruling seems to somewhat conflict with a previous ruling by the en banc 9th Circuit, so there is a good chance that it will be appealed to the full court. In the meantime, though, it is conceivable that a sleazy lawyer could file federal charges against people who use pseudonyms to continue participating in an online forum where they have been previously banned for pointing out the ignorance and irrationality of certain protected members.
It’s reassuring that we don’t know of anyone with the combined lack of self-control and ethics that would allow him to do such a thing.