When officers Chen and Bradford are chasing the first escaped inmate, skid marks on the road are visible from earlier takes.
California is NOT an open carry state so, by having their weapons out in the open alone, the vigilantes could have been arrested. In addition, pretty much all the weapons they are carrying violate California gun laws which, among other things, bans the possession of 'hi-cap' magazines.
At the end when Nolan hands her the pen it is from front he hands her the pen with his right hand. In next shot from behind her he is handing her the pen from his left hand.
The militia men all claim to have permits for the weapons. California does not require a permit to purchase or own a weapon, only a background check and waiting period.