Final answer:
Selling alcohol to a minor is illegal according to the National Minimum Drinking Age Act of 1984.
Step-by-step explanation:
The selling of alcohol to a minor is considered illegal in the United States. The National Minimum Drinking Age Act of 1984 requires states to set the minimum drinking age at 21, or else they face a reduction in federal highway funds. Therefore, if a bartender were to sell a beer to a minor, it would be a violation of the law.