I had a look at Maritime and steps aboard may not be correct - reference is made to a handover including maintenance required and other thing but also a sign off and on. I assume this to be on the bridge and in the log.
But it seems the signature is required to be the "Captain".
Should the Captain of an aircraft not be happy with a passenger or a legal fuel load given to him to begin a flight, the Captain can simply start and begin to "taxi under own power" assume ultimate authority request a return to gate and have a passenger remover or more fuel added.
So any input from a Captain would be considered and discussed and hopefully agreed prior to pushback by any and all responsible persons.
It is comforting to see some have noticed that there is a legal void in who maybe responsible and that may be a big issue if things go real bad one day.
Is it not best to clear the legal mud that we currently have?