Ok, here's what you do. Go to whois and find the address info. Then go over to his place (if it's not a PO Box) and kill him. Problem solved. That's what I do and I haven't had any copycats in about 2 months now.
Seriously though, just be flattered and move in. Put all your energy into making money and reading GFY so that you can get Paid In Full(80's flashback: Eric B. & Rakim). I have people copying my designs once in while and it makes me chuckle.
Imitation is the highest form of flattery!