It’s one of the seemingly ironclad rules of adolescence: In the United States, you can’t drink legally until you’re 21. Of course, our underage consumption laws are flouted regularly. More than half of American 20-year-olds have tried alcohol at some point in their lives, according to the most recent numbers from the National Survey on Drug Use and Health.

But as it turns out, not all of that underage drinking is, strictly speaking, illegal: At least 37 states have some sort of exception in their drinking laws that allow underage people to drink at home and within the company of family members. According to the National Institute on Alcohol Abuse and Alcoholism, the patchwork of state laws governing exceptions to statutes on underage alcohol possession looks like this when simplified: