When does a Captain's Authority start
My understanding garnered from a few years ago (actually longer than I wish to admit to) was that the 'Authority' of the Captain was only established when the doors were closed.
While the aircraft was at the airbridge, or connected in another way to ground support, then the jurisdiction was still vested in the local plod (or airport authority).
Somewhere in my archaic filing system, I have the precedent authority - originally derived from the Hague Convention.
Now a boarding pass would constitute an 'instruction' but that is issued well before a captain or crew member takes 'command'.
So it begs the question - when does an 'instruction' given by the CC or TC become a 'lawful command'. Same sits with Maritime Law from whence our Aviation Law was derived.