Cal. Food & Agric. Code § 24009

Whether a horse is in competition or not, refusal to submit a horse in an event for examination, or refusal to cooperate with the licensed veterinarian, or his or her technicians and agents, shall constitute a violation of, and subject the responsible person to, the same penalties that are applicable to prohibited substances or permissible substances under Section 24007. A suitable sample shall be collected from a horse selected for testing by a drug testing agent of the department unless the agent releases the horse from testing.