Another issue you guys might want to consider is the concept of female-on-male rape. If a man is drunk to the point where he cant consent to sex, can a women be held responsible for rape? I'm not offering an opinion on this, but it's an interesting little issue which we looked at in Criminal Law at uni (prior to a few years ago, female on male rape was impossible as rape required "penetration" back then). It's a rare occurance and extremely difficult to prove, but it does happen.
Also, if both parties are drunk and engage in 'consented' sexual activity and this consent would not be granted by both parties in a sober state then who is the rapist?
Consider the situation where person A wants to engage in sexual activity with person B (let's ignore the gender to prevent stereotype bias). It is expected that if person B denies consent, that person would communicate this to person A and if person A continues to advance then that is getting into rape territory. That' pretty black and white and I'm sure everyone knows this.
Now this where things get complicated.
Assume person A would not advance if no consent is given by person B. In the event that person B grants 'consent' to person A but is in a drunken state, how is person A supposed to know if this consent is the real intention of person B in his/her sober state? Person B might actually consent in the sober state anyway or may not consent in that state.
Now let's further complicate this kind of situation where person T is drunk and is making advances to person S. These advances may or may not be reflective of what person T would do in a more sober state. If person S provides consent to those advances then is person S raping person T? (if person T would not do such a thing in a sober state - and this information is not known by person S nor was it communicated by person T to person S)
There is also the grey area of how do you tell how drunk a person has to be such that his/her decision making is not reflective of those in his/her sober state - it is too subjective. A person might be drunk but not drunk to the point of being unable to make proper decisions but from another person's perspective this may be different.
The unfortunate reality is that this situation is almost always viewed as a person 'taking advantage' of another person when it can be much more grey and complicated than that. Of course those 'taking advantage' situations do exist but it would be incredibly naive to think that ALL situations are like that.