I run a forum for supporters of a sports club. I often get supporters from a rival club coming in, creating a user, and spamming my forum, most often after we lose a big game, particularly if against a team they support. I ban them, but they keep coming back with new accounts.
By "spamming", I mean that they keep posting random shit, like pictures and GIFs ridiculing our club. Also a lot of swearing and insults.
Is this illegal? Can the authorities be involved in any way? The forum is international but US-based.
Note that I am asking out of curiosity. I don't expect this to be a practical approach in any way, and I also realize a better method is to simply secure my site better against repeat-offenders.