i. Children cannot consent
The legal age of consent varies from state to state in the US. They vary between the federal age of consent which is 16 years old and 18 years old. Some states have a “close in age law” that protects children who are 2-3 years older than the person who is not of legal age to consent.
To learn more about the age of consent, click here
ii. People with severe intellectual disabilities (formerly known as severe retardation) cannot consent
If someone has a severe intellectual disability that does not allow them to understand exactly what is happening, or if their IQ and reasoning ability is that of a child, they cannot consent to sex.
iii. Intoxicated people cannot consent with someone who is sober
If someone is intoxicated from beer, liquor or drugs, they are unable to consent. If both people are severely intoxicated,, however, it does not mean that they raped each other. It is similar to two children who are below the age of consent having sex: It is wrong, but not an offense that is triable in court.
If one person is clearly intoxicated beyond the point of consent and the other person still chooses to have sex with them, that is rape
Of course, there may be instances where the court has to decide with evidence if someone was too intoxicated to consent to sex. A good example of this is in Degrassi: The Next Generation between Season 12 episode 22 and Season 13. If you follow the Zoe Rivas case specifically, this topic is the main focus. You can watch on YouTube for free
I actually had to explain this to grown men and two who were sincerely upset that they could not have sex with a drunk girl without being considered a rapist. This boggles my mind as to why they would even want to.