need some help here...

does anybody knows where to find the information about the rules and regulation of overtaking in a race?
last weekend i have a kart racing session with some folks, and there was an accident where my friend got hit from behind by the guy behind him. the guy said that my friend was too slow, and didn't give him a chance to overtake, so he thought the only way for him to get faster was by getting rid off my friend at the front.
my friend was really pissed off, and told the guy that he can not overtake someone like that. and he thought that he has the right to defend his position and close any door that would allow that guy to overtake him.
until today, we're having a serious argument among us in regards to the overtaking rules, ethics, and stuff, to be applied on our next racing sessions.
so guys, would appreciate any advise on this matter...
thanks and cheers!
Yoq
