If you wanna go the violent way of curing stupidity, just hit him every time he does something stupid, and escalate the punishment when he repeats past mistakes. It really does work.
If you wanna be non violent about it, tell him if he doesn't wanna follow the rules he can get the fuck out.
As far as I'm concerned, there's no difference between a real firearm and an airsoft gun in CQB. Both can bounce and both can cause shrapnel.