LSM
Your captain's authority does not include the power of arrest, as you confirm by saying "I can have someone arrested" but you can make a ctizen's arrest, the difference being that you must have evidence of a crime and a passenger acting very aggressively is providing that, where as an authorised person can arrest on suspicion (e.g. a policeman.)
Having said that, I can do the same thing from seat 6F, without your permission (doors open.)
If you try to stop the policemen, you will be arrested at some stage. I am a little surprised that an airline captain is not aware of this, as airlines normally cover this type of thing in command courses.
In flight, the authority is a very different manner, e.g. AA the recent ''we are landing move all the traffic out of our way" indicent at JFK and the captain can override other laws in the interests of safety.
I'm not downgrading the captain's authority and recognise that this is an industry concern, but am just pointing out that the authority varies between air and ground.