That's a poignant philosophical observation:

YES, someone says it. I'm so tired of people bringing up laws when I'm arguing over morals. Let morals change your laws, not the other way around

Regretting a decision has nothing to do with consent. Just because you consented to something does not mean you won't regret it or vice versa.

As far as legality is concerned, you need two key things to be able to give consent: Knowledge of what you’re consenting to, and then the actual consent.

The second part is very straightforward, so I’ll touch on that first. Because if someone is unconscious, they obviously can’t consent. It’s an easy argument to satisfy; If they didn’t/couldn’t say it was okay, then it wasn’t okay. Easy. They were passed out? Then they couldn’t consent.

The big reason it can get murky is because that communication can happen nonverbally, via body language and context. Maybe someone misinterprets a signal, and goes in for a kiss that the other person doesn’t want. That’s a tame example, but it gets the point across with how the actual communication could get murky. But again, this is certainly the most straightforward part of consent. Can they say yes? Did they say yes? Cool.

The tricky part is that first one: Knowledge of what they’re consenting to. It gets tricky because the line gets blurry when alcohol is involved. The most straightforward times this gets violated are when one partner is surprised by something. “Stealthing” (taking a condom off without the other person’s knowledge) is rape because it violates this first part of consent. They weren’t given sufficient knowledge of what they were consenting to, (because they believed their partner was wearing a condom) so it isn’t consensual. Everyone involved needs to be able to comprehend what is happening when it’s happening. You can be blackout drunk but still able to understand what is happening in the moment. Being blackout just means the “record” part of your brain was turned off. But you can still be awake and aware of your surroundings, even if you won’t remember any of it once you sober up.

This is why lots of rape cases get thrown out. The victim was enthusiastically consenting at the time, but doesn’t remember it because they were blacked out. They wake up the next morning and are horrified about what they participated in. If they were blackout, they may not even remember consenting at all. But if they were capable of understanding things at the time that it was happening then the first part is still (as far as the law is concerned) satisfied. The law doesn’t care if you regret it after the fact, or if you can’t remember consenting, or if you only consented because your inhibitions were lowered and you had beer goggles on. All the accused rapist has to do is prove that you were able to understand what was happening, (or at least convince the jury that you were) and that you went along with it with that knowledge. If they’re able to do that, (and if the jury isn’t biased) then they’ll be acquitted. Because as far as the law is concerned, if those two parts of consent are fulfilled, then you were able to consent.

The courts do take a lot of factors into consideration, but generally speaking, voluntary intoxication has a high threshold to meet. The victim usually needs to be passed out (or at least so drunk that they’re not capable of communicating their consent). Because the courts will go “well they knew what they were doing until they passed out, because they knew they were intoxicated.” Involuntary intoxication (like having a drink spiked) is typically a much much lower threshold. If a victim was drugged, they’ll have a much easier time proving non-consent, because courts will tend to go “well they didn’t intend to get intoxicated, so any consent they gave while intoxicated should be considered coerced.”

If your drinking you tend to forget your judgement is impacted.

Yeah, its seems in Canada law it depends on the circumstances. You can't consent if you're unconscious or if you've been drugged, or coerced... and, yeah, those seem to me like obvious cases of rape. But going by this article, two people being drunk doesn't automatically negate consent so long as they're both aware and willing.

Article Summary:

Consent is defined in the Criminal Code as "voluntary agreement of the complainant to engage in the sexual activity in question." Janine Benedet, a law professor at the University of British Columbia's Peter A. Allard School of Law, puts it this way: "The question is whether the person in their own mind wanted this sexual activity to take place." According to the code, no consent is obtained when the agreement comes from someone other than the complainant, the person is incapable of consenting or is induced by the accused abusing a position of trust, power or authority. Consent also does not exist if someone "expresses, by words or conduct, a lack of agreement to engage in the activity" or if the complainant, who previously consented, expresses "a lack of agreement to continue to engage in the activity."

In that decision, the court wrote that "when the complainant loses consciousness, she loses the ability to either oppose or consent to the sexual activity that occurs. "Finding that such a person is consenting would effectively negate the right of the complainant to change her mind at any point in the sexual encounter."

The code says there is no consent where someone is incapable of consenting. Various factors affect an individual's capacity to voluntarily agree to sexual activity, according to Canadian law. One factor courts sometimes consider is whether the accused was in a position of authority, said Benedet. "There are provisions in the Criminal Code that talk about consent being vitiated when someone is in a position of trust or authority," she said. Despite the idea of a position of trust impairing the ability for there to be consent, Benedet said there continues to be debate in the case law about "what kind of relationship really puts you in a position of authority."

Intoxication is also considered a factor that affects a complainant's capacity to consent to sexual activity. But in practice, Benedet said, the threshold of intoxication at which point someone is deemed incapable of consent varies depending on the circumstances. Where a complainant becomes intoxicated involuntarily, for instance, by being drugged, "courts [tend] to be very generous in terms of what level of intoxication would be sufficient to amount to incapacity." If a complainant consumes drugs or alcohol by choice, courts have "a very high threshold for incapacity, much higher than they would have applied in those involuntary intoxication cases."

But what if both people are on MDMA? I know I get very horny on it and fall in love with everything.

[Granted,] consent can be removed at any point but if neither party states/shows intention to back out it is safe to assume that there was consent during the act even if both parties were drunk because they’d agreed to it beforehand.

And a state of intoxication can prevent someone from being able to express the desire to remove consent. It is entirely possible to start an encounter with that capability, and have an intoxicant ingested before the encounter take away that capability after the encounter has begun.

Let's complicate the hypothetical further: Both parties are fully sober, and agree to a sexual encounter, in which Party One will pretend to be blacked out. Party One ingests an intoxicant in secret, and actually blacks out after the encounter has begun. Is Party Two guilty of a crime?

So .... they raped each other? They could both go to jail?

I didn't pose the question to argue in the comments. That said, I would argue that the question I raised is very different from the question you've rephrased. It's obvious that if you (being drunk) force yourself on someone who is sober, then that is rape; it is less obvious whether two drunk people who think they're giving consent can (morally/ legally) give consent.

Here I don't mean to argue against your interpretation of consent because I wanted to hear different opinions in the first place. I just don't think that's a fair rephrase of the question because it renders the original question trivial.