I don't sell beer to minors

When it comes to selling you beer, I will sell you none.
You have no identification and you look under twenty-one.
You come here and try to buy beer every day.
I won't sell you any so you might as well go away.
I'm going to pop you in the eye and give you a shiner.
You'd better learn that I don't sell beer to minors.

(Even though this is a fictional poem, it's important to keep alcohol beverages out of the hands of minors.)