How do I tell my friend to back off ?

Alright, my guy friend is constantly flirting with someone, it's just how he is, but he doesn't think he's flirting. My friends all say he flirts with me, and he knows I have a boyfriend. Whenever I think he is crossing the line, I walk away or stop talking to him. But is there anyway I can make him stop for good ?


Thanks in advance. (:How do I tell my friend to back off ?
Two words. BACK OFFHow do I tell my friend to back off ?
a swift kick in the nuts will do it