California Code, Business and Professions Code - BPC § 25663

(a) Except as provided in subdivision (c), no licensee that sells or serves alcoholic beverages for consumption on the premises shall employ any person under 21 years of age for the purpose of preparing or serving alcoholic beverages.  Every person who employs or uses the services of any person under the age of 21 years in or on that portion of any premises, during business hours, which are primarily designed and used for the sale and service of alcoholic beverages for consumption on the premises is guilty of a misdemeanor.

(b) Any off-sale licensee who employs or uses the services of any person under the age of 18 years for the sale of alcoholic beverages shall be subject to suspension or revocation of his or her license, except that a person under the age of 18 years may be employed or used for those purposes if that person is under the continuous supervision of a person 21 years of age or older.

(c) Any person between 18 and 21 years of age employed in any bona fide public eating place, as defined in Sections 23038 and 23038.1, which is licensed for the on-sale of alcoholic beverages, may serve alcoholic beverages to consumers only under the following circumstances:  such service occurs in an area primarily designed and used for the sale and service of food for consumption on the premises;  and the primary duties of the employee shall be the service of meals to guests, with the service of alcoholic beverages being incidental to such duties.  For purposes of this subdivision, “serve” or “service” includes the delivery, presentation, opening, or pouring of an alcoholic beverage.