Pursuant to US and state laws under 23 U.S.C. 158, it is illegal for persons under the age of 21 to purchase alcoholic beverages. It is a Class 1 Misdemeanor for a business to sell alcohol to an intoxicated person.
However, there is nothing to prevent a business from selling alcohol to a sober, 21+ individual who is a current or recovering alcoholic. Alcoholism is a disease that destroys lives and families. Allowing these individuals to continue drinking legally should be stopped.
If an individual has been arrested for 3 or more crimes, whether vehicular, violent, etc, their license/ID should indicate them as being an "Alcoholic" for a period of 1-5 years from the last incident date. It should then be a Class 1 Misdemeanor to sell alcohol to these individuals.