California Codes, Business and Professions Code - BPC, Division 8 — Special Business Regulations, Chapter 2 — Boxing, Wrestling, and Martial Arts, Article 3 — Jurisdiction, Licenses, and Exemptions, Section 18653

No person shall train a professional boxer or kickboxer or martial arts athlete unless he or she has been licensed by the commission. A professional trainer is someone who is responsible for the day-to-day training of those athletes and possesses a minimum of five years experience in combative sports. Only professional trainers licensed by the commission may make a recommendation to the commission on whether a contestant is prepared for his or her first amateur mixed martial arts bout or to turn professional in boxing, kickboxing, or mixed martial arts. A professional trainer shall be present in the corner of the contestant unless otherwise authorized by the commission or the executive director.