So… just looked it up. Ya’ll are right, looks like individual stores will prohibit you or maybe a local law in a county prevents them selling to minors, but there is no regulation at the state or federal level that prevents anyone from buying energy drinks. I was always told I couldn’t purchase them so I assumed it was a regulation thing.
That, and my parents both worked in the medical field and wouldn’t let me buy any until I was 16 anyways. Something about they can f**k up your heart if you drink too many in one go.