California Code, Business and Professions Code - BPC § 19941

(a) A person under 21 years of age shall not do any of the following:

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

(c) A 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 a 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.