I can't believe there are people are actually considering this question.
If the Commander smells of alcohol, then the flight stops there and then. Fullstop, period. They may not be drunk but they are almost certainly over any limits.
And then he/she deserves the book thrown at them. They are responsible adults, they have to face the music, no matter how many bleeding heart liberals on this board think otherwise (along the lines of "I think you better report sick sir")
And I have no sympathy for those on this board that consider anything else acceptable.