No offense, but this is why paintball gets such a horrible reputation. Granted that f you guys are on private property where the owner gave you permission to play, you technically aren't breaking any laws.
However, not playing at official fields where safety actually matters, and doing something as stupid as what your friends did, is exactly what gives paintball such a bad reputation and keeps it from becoming more mainstream. Some towns have even outlawed paintball!!
We played in a kids backyard & the kids dad was a cop who let us so I don't think we were breaking the law.