(A) No person, either directly or indirectly, by himself, clerk, agent, servant or employee, shall at any time knowingly or negligently sell, furnish, give or deliver any alcoholic liquor to any person unless such person shall have attained the age of 21 years; provided, however, that nothing herein contained shall prohibit the sale of alcoholic liquor to a person under 21 years of age upon authority of and pursuant to a prescription of a duly licensed physician.
(B) In a prosecution for the violation of this section, proof that the defendant or the defendant’s agent or employee demanded and was shown, before furnishing alcoholic liquor to a person under 21 years of age, a motor vehicle operator’s license or registration certificate issued by the federal selective service or other bona fide documentary evidence of the age and identity of that person shall be a defense to a prosecution under this section.
(1990 Code, § 9.124)