Cal. Bus. & Prof. Code § 19941

(a) A person under 21 years of age shall not do any of the following: (1) Play, be allowed to play, place wagers at, or collect winnings from, whether personally or through an agent, any gambling game. (2) Be employed as an employee in a licensed gambling establishment except in a parking lot, coffee shop, restaurant, business office, or other similar room, as determined by regulations, wherein no gambling activity or activity directly associated with gambling takes place. (3) Present or offer to any licensee, or to an agent of a licensee, any written, printed, or photostatic evidence of age and identity that is false, fraudulent, or not actually his or her own for the purpose of doing any of the things described in paragraphs (1) and (2). (4) Loiter in or about any room in which any gambling game is operated or conducted.

(b) Any licensee or employee in a gambling establishment who violates or permits the violation of paragraphs (1) to (3), inclusive, of subdivision (a) is guilty of a misdemeanor.

(c) Any person under 21 years of age who violates this section is guilty of a misdemeanor.

(d) Proof that a licensee, or agent or employee of a licensee, demanded, was shown, and acted in reliance upon bona fide evidence of age and identity shall be a defense to any criminal prosecution under this section or to any proceeding for the suspension or revocation of any license or work permit based thereon. For the purposes of this section, “bona fide evidence of age and identity” means a document issued by a federal, state, county, or municipal government, or subdivision or agency thereof, including, but not limited to, a motor vehicle operator’s license or an identification card issued to a member of the Armed Forces, that contains the name, date of birth, description, and picture of the person.