A piece of advice from a mod of a forum a bit larger than this one.

There is a certain class of user we call "legal trolls". This type of troll aims to undermine moderation staff and silence critics by looking for loopholes in the forum rules/netiquette, deliberately misunderstanding wording in forum rules/netiquette and deliberately misapplying legal terms or citing laws that are not even applicable to the forum in question.

It is the digital equivalent to the real world situation where a guy is tying up bouncers in discussion at a club when he is not allowed to enter.

The matter of legal trolls was discussed with our lawyer who came to the following conclusion.

[paraphrased]The solution is of course to remove the offending user from the premises. An internet forum is the digital equivalent to a private club. The club owner is well advised to remove club members that are souring the club by harassing club staff or other club members. He is also well within his rights to do so. Note also that this does NOT constitute an infringement on free speech, because free speech laws in all jurisdictions apply to the relation between government and citizen, NOT to relations between citizen (club owner and stuff) and citizen (club members). [/paraphrased]