Dude, this can open a whole crap load of issues.
-If they are playing on private property, they had better be aware of the local bylaws.
-If they are playing in view of the public, the police will be called in, and it'll only take one idiot to screw things up.
-If they are playing where it is all good with the bylaws, not in view of the public, and not trespassing, there had better be parental presence....a parent or adult that WILL take responsibility if something happens...legal responsibility.
It's better that these under aged games get organized at insured paint ball fields where each of the participants have a parent (or legal guardian) present. It'll save us all a world of headaches.