Simple really and has already been mentioned. The Tokyo Convention is quite specific. While Aviation Law has it's derivation in Maritime Law, the accepted proposition in Australia is 'release' of the aircraft. That means doors closed and the airbridge detached. We did have an instance around passenger injury once when the airbridge had to be moved to allow 1L to be closed and locked. I do not have the judgement in front of me to quote.... but the clear issue was 'release' (same as the mooring lines coming off a ship). The captain, irrespective of seniority / rank etc has no 'authority' on the ground - he / she may 'request' but until they have 'control' of the aircraft, the implied authority does not exist. Think in terms of a sworn officer who has access to the aircraft. While the door is open, that officer may enter and enforce the law. Even a return to the airbridge - the Senior Pilot can elect to make that return, but will need to request the sworn officers of the resident jurisdiction to enter the aircraft once it is no longer under 'command'. 'Command' in this context is taken to be 'the ability to independently control the operation of the aircraft, including giving instruction to other persons to give effect to that control (think push back tug).