Agaricus - I agree that the ANO is very clear on the question of drunkenness. The ANO is in itself pretty strict as to what it prohibits generally. I suspect that this is largely to ensure that the captain has some sort of legal backing when having to make a decision, so as to know he/she won't get sued subsequently. The ANO has the potential to be used as a legal catch-all when it is dubious whether a different charge would be upheld in court. An example of such a catch-all was Al Capone being imprisoned for tax evasion rather than his more reprehensible mafia activities
Just because law gives a person or organisation legal authority to do something, doesn't mean it is necessarily a sensible thing for a person to act in such a way. A recent example, was local councils using terrorism legislation to check whether a child enrolled at a school was living within the formal catchment area. The council was entirely within its rights to do this - but there was a signiciant area of public opinion that held this to be over-reacting. In the same way, the police could round up large numbers of people walking around a town just after pubs close and lock them up for being drunk on the pavement. Entirely within their rights, but the police would be heavily condemened for over-reacting if they were to do so.
I suspect that in December every year, there are plenty of people all over Eruope who as an office Xmas party, fly off somewhere short haul, have a long boozy lunch and then fly home at the end of the day. As captain, you can refuse them permission to board the plane if you should so choose and be entirely within your legal rights. Problem is what to do if those same passengers happen to hold platinum airline loyalty cards and each spend tens of thousands with your airline every year and are likely to be very unhappy if refused their flight home. How would the police at the airport react if the captain orders 20 tipsy travellers be arrested on the grounds of being tipsy in a plane, knowing full well the airline serves free alcohol to its passengers ? What would the marketing dept say to the chief pilot's office if a large number of complaints of this nature were received every December ?
No, get the drunken sot off to sober up un terra firma, and then he can buy another ticket when sober.
Is that really necessary ? Perhaps if someone is really drunk but not causing any other particular problem, ground staff could give the passenger a bottle of tap water and put them on waitlist for the next flight instead ?
My point is that a captain cannot operate in isolation. The ANO gives him/her legal backing to act, but also has to justify their actions within a company that exists to make a profit. And yes, there is a potential for conflict of interest