Cal. Code Regs. tit. 4 § 1894
Trainers are responsible for the condition of horses in their care and are presumed to know the rules. A trainer represents the owner relative to horses which he is training in the matter of entries, declarations, and the naming of jockeys or drivers, unless the owner notifies the stewards in writing to the contrary. A trainer is responsible for the timely attendance of his horse at the receiving barn and paddock and he shall attend his horse in the paddock and be present to supervise the saddling except when relieved of such duty by the stewards. No trainer shall delegate or sublet his duties as a trainer except as provided in this article, nor shall a trainer have any interest in the earnings, winnings, or bonuses of any other trainer.
Cal. Code Regs. Tit. 4, § 1894