What counts as proper consent will no doubt vary based on whether the matter is considered in moral, practical or legal contexts.
What is also not in doubt is that people will disagree considerably about this matter.
Another reason for this is definitional: most (if not all) colleges have a policy that sexual activity with an intoxicated person is, by definition, sexual assault.
While the practical and legal aspects of this are important, I will focus on the matter from the standpoint of morality.
It might be countered that as long as a person can engage in consent behavior, the person still has agency of consent. This does have considerable appeal in that the only practical way to determine consent is by observing external behavior.
After all, a person does not have epistemic access to the mental states of other people and cannot discern whether the “yes” is a proper “yes” or merely “yes” behavior without true consent.
It is worth noting that a decent person would certainly take into account apparent intoxication and out of a sense of ethics or politeness refuse to accept what seems to be offered freely. ” I certainly would not take his car—even though doing so would hardly be theft.
To use an analogy, if one of my friends is drunk and says “I love you man, here take my car. Likewise, if a woman is drunk but making it clear she wants to have sex with a man, the decent thing for the man to do is refuse, escort her safely home and, if necessary, guard her from the less virtuous when she passes out.
Somewhere in this large territory lies the point at which a person loses her consent agency and is incapable of actual consent.
One obvious problem with finding the boundary at which consent agency ends is that this point might occur well before a person has lost the capacity to engage in behavior that would indicate clear consent by an unimpaired person.
This is because intoxication reduces a person’s ability to understand and to consciously agree (or, as people say, being drunk makes you stupid).
When the person has no consent agency at all, having sex with that person would clearly be rape (that is, sex without consent).
When I wake up the next morning and find the empty boxes and White Castle receipt, I could hardly claim that White Castle committed theft by accepting my money.