Via the Liquor Control Act of 1934----
235 ILCS 5/6‑20) (from Ch. 43, par. 134a)
Sec. 6‑20. Transfer, possession, and consumption of alcoholic liquor; restrictions.
(a) Any person to whom the sale, gift or delivery of any alcoholic liquor is prohibited because of age shall not purchase, or accept a gift of such alcoholic liquor or have such alcoholic liquor in his possession.
(b) If a licensee or his or her agents or employees believes or has reason to believe that a sale or delivery of any alcoholic liquor is prohibited because of the non‑age of the prospective recipient, he or she shall, before making such sale or delivery demand presentation of some form of positive identification, containing proof of age, issued by a public officer in the performance of his or her official duties.
(c) No person shall transfer, alter, or deface such an identification card; use the identification card of another; carry or use a false or forged identification card; or obtain an identification card by means of false information.
(d) No person shall purchase, accept delivery or have possession of alcoholic liquor in violation of this Section.
(e) The consumption of alcoholic liquor by any person under 21 years of age is forbidden.
(f) Whoever violates any provisions of this Section shall be guilty of a Class A misdemeanor.
(g) The possession and dispensing, or consumption by a person under 21 years of age of alcoholic liquor in the performance of a religious service or ceremony, or the consumption by a person under 21 years of age under the direct supervision and approval of the parents or parent or those persons standing in loco parentis of such person under 21 years of age in the privacy of a home, is not prohibited by this Act.