I suggest the fastest way to get a result may be to do the whois lookup Cap Loko suggested and then get a lawyer to write a very nasty "cease or desist" letter, mentioning "unlimited fines" and "Incarceration".
If you can't get the personal information from the whois lookup (they may have used an intermediary company to protect their identity) just approach the intermediary (they won't put up fight).
The above is all without any warranty and let us know how you get on!
(The aim of the above is to get the content taken down. I also suggest you look into suing for damages - free money!)