No person shall sell, give or otherwise supply alcoholic liquor or beer to any person knowing or having reasonable cause to believe him to be under legal age, and no person or persons under legal age shall individually or jointly have alcoholic liquor or beer in his or their possession or control, except in the case of liquor or beer given or dispensed to a person under legal age within a private home and with the knowledge and consent of the parent or guardian for beverage or medicinal purposes or as administered to him by either a physician or dentist for medicinal purposes and except to the extent that a person under legal age may handle alcoholic beverages and beer during the regular course of his or her employment by a liquor control licensee or beer permittee under state laws.