Cal. Bus. & Prof. Code § 4857

(a) A veterinarian licensed under this chapter shall not disclose any information concerning an animal patient receiving veterinary services, the client responsible for the animal patient receiving veterinary services, or the veterinary care provided to an animal patient, except under any one of the following circumstances:
1. (1) Upon written or witnessed verbal authorization by knowing and informed consent of the client.
2. (2) Upon authorization received by electronic transmission when originated by the client.
3. (3) In response to a valid court order or subpoena.
4. (4) As may be required to ensure compliance with any federal, state, county, or city law or regulation, including, but not limited to, the California Public Records Act (Division 10 (commencing with Section 7920.000) of Title 1 of the Government Code).
5. (5) If the care or service was for a horse that has participated in the previous year, or is intended to participate, in a licensed horse race. In these situations, the entire medical record for the horse shall be made available upon request to anyone responsible for the direct medical care of the horse, including the owner, trainer, or veterinarian, the California Horse Racing Board or any other state or local governmental entity, and the racing association or fair conducting the licensed horse race.
6. (6) As otherwise provided in this section.
(b) This section shall not apply to the extent that the client responsible for an animal patient or an authorized agent of the client responsible for the animal patient has filed or caused to be filed a civil or criminal complaint that places the veterinarian’s care and treatment of the animal patient or the nature and extent of the injuries to the animal patient at issue, or when the veterinarian is acting to comply with federal, state, county, or city laws or regulations.
(c) A veterinarian shall be subject to the criminal penalties set forth in Section 4831 or any other provision of this code for a violation of this section. In addition, any veterinarian who negligently releases confidential information shall be liable in a civil action for any damages caused by the release of that information.
(d) Nothing in this section is intended to prevent the sharing of veterinary medical information between veterinarians and peace officers, humane society officers, or animal control officers who are acting to protect the welfare of animals.
(e) Nothing in this section is intended to prevent the sharing of veterinary medical information between veterinarians and facilities for the purpose of diagnosis or treatment of the animal patient that is the subject of the medical records.