Question: is it illegal to be in possession of alcohol under 21

Answer: Yes, In the United States, a Minor in Possession, or a MIP, (also referred to as a PAULA, Possession of Alcohol Under the Legal Age) is illegal, typically a misdemeanor. In California, depending on the county in which the person is charged, the crime may also be charged as an infraction. Anyone who is under the age of 21 and possesses alcohol in the United States, with the exception of special circumstances, is violating the law of the state.