California Code, Business and Professions Code - BPC § 19520

(a) Every person not required to be licensed under Article 4 (commencing with Section 19480) who participates in, or has anything to do with, the racing of horses, including a horse owner, jockey, driver, apprentice, exercise rider, agent trainer, stable foreman, groom, valet, horseshoer, stable watchman, outrider, and every employee of a parimutuel department, shall be licensed by the board pursuant to rules and regulations that the board may adopt, and upon the payment of a license fee fixed and determined by the board. Any license issued pursuant to this article shall include a current photograph of the licensed person.

(b) No person required to be licensed by this article may participate in any capacity in any horse race meeting without a valid and unrevoked license authorizing the participation.

(c) The board may adopt regulations to require outrider license applicants to pass both a written and an oral examination and to authorize outriders to exercise the duties and powers of the board set forth in Section 19440 as are delegated by the board.