Reading the rules of flying, I see that not only is it a violation of regulations for any person to operate any aircraft while drunk - it also is a violation for any person to transport a drunk person by air.

What is that supposed to mean?

Alcohol is commonly served aboard. Some passengers get drunk and engage in air rage. They can be arrested and prosecuted - but so can passengers who engage in air rage while sober.

The regulations seem to talk of transporting any person who is drunk.

So... What exactly happens to a passenger who drinks too much and is unable to wake up and deplane?

What happens to a passenger who, though visibly drunk, is capable of deplaning as usual and has given no offence? Has he or she committed any offence?

The airplane captain does appear to have violated the regulations if, at any time during the trip, any passenger in the cabin has been drunk!