Ultimately it is the Captain who is responsible to call the Airport Police to the aircraft. The Captain is the one responsible for all actions taken on his aircraft....And I would expect the Captain to at least be called in for tea and biscuits..
Ummm.... Sorry but whilst some like to think so it is not that simple. In the air, yes, but on the ground, with the doors open, with law enforcement on the scene of an incident it is nowhere near as clear cut.