He can be prosecuted.
Some teens recently found that out.
Students Arrested for Cyber Bullying
http://www.freerepublic.com/focus/f-news/1315493/posts
And, a web forum I was a member of many years ago had a slime posting troll much like this one.
They had their internet access permanently taken away through legal means.
The catch was that we had to document their pattern of behavior, and show a pattern of harassment and stalking.
Took two months, but it worked.
Then that forum tanked.
*snort*
This has been happening long enough that we should be able to ddocument patternss.