Malum prohibutum vs malum in se: "wrong [as or because] prohibited") an unlawful act only by virtue of statute, as opposed to conduct that is evil in and of itself.
Depending on the state, or country, you live in, and ignoring some philosophical questions of federalism, this scout's possession of MJ is illegal simply because he is not yet 21.
When I was a senior in high school I could legally purchase and consume alcohol approximately three hundred yards from my back door but not thirty feet down the street from my front door simply because I had stepped over a state line. Today, if