California Code, Business and Professions Code - BPC § 19583.9

(a) All horses at a licensed thoroughbred, fair, or quarter horse race meet shall be subject to veterinary monitoring during morning training.  A licensed trainer and their staff shall be required to cooperate fully with all requests made by board-licensed veterinarians and outriders.  All examining veterinarians at a race meet conducting live racing shall be under the direct supervision of the official veterinarian or the equine medical director.

(b) A trainer shall not administer, directly or indirectly, or otherwise permit to be administered, any medication to a horse under the trainer's care that is racing or training at a board-approved racetrack, unless the medication is prescribed for that specific horse and administered strictly in accordance with board regulations.

(c) A trainer shall not apply to a horse's feet on racing day any type of topical medication designed to alleviate pain, soreness, or tenderness of a horse's feet.

(d) The use of diagnostic imaging shall be an accepted component of prerace examinations by an examining veterinarian.  The official veterinarian may order the diagnostic imaging if they believe that the use is warranted.  In addition, video footage may be used and maintained by the official veterinarian for the purpose of comparison when a horse is removed from the Veterinarian's List.