Seriph........... I, or I'm sure (imho) many of us, do not understand why you seem to find the contents of an Airlines Ops manual such anathema ( it's a legally binding tome; i.e. containing details about which you can be veritably hung drawn and quartered ), and accordingly might I suggest you have a VERY GOOD READ of your own companies one (start with 'Part A' - Section 1 - in which you'll find somthing akin to 'Authorities, Duties and Responsibilities of the Commander' ), especially those sections which pertain to who is responsible for what, where, and when - because one day you might need to be able to defend both your actions and that of your crew ( should either you or they vary from what is permitted within it and or its scope ).
Indeed you might indeed find that, following the section mentioned above, there is something relating to 'The Duties and Responsibilities of Other Crew Members' (but not the F/O - but whom is governed by similar dictates) stating something similar to: 'Other crew memvers are responsible to the aeroplane commander and shall carry out his / her instructions and assist him / her in the safe operation of the aeroplane'
So read it and weep old son - it's black and white (sort of) and legally binding - ignore it or misunderstand it at your peril !