Drinking under 21 isn't illegal federally: https://www.law.cornell.edu/uscode/text/23/158 https://www.law.cornell.edu/uscode/text/23/158 It's just that if you

Drinking under 21 isn't illegal federally: https://www.law.cornell.edu/uscode/text/23/158 https://www.law.cornell.edu/uscode/text/23/158 It's just that if your state doesn't set their drinking age to a minimum of 21, they'll lose a big chunk of federal highway funding.