Cal. Pen. Code § 599e
Every animal which is unfit, by reason of its physical condition, for the purpose for which those animals are usually employed, and when there is no reasonable probability of that animal ever becoming fit for the purpose for which it is usually employed, shall be by the owner or lawful possessor of the same, deprived of life within 12 hours after being notified by any peace officer, officer of said society, or employee of an animal shelter or animal regulation department of a public agency who is a veterinarian, to kill the animal, and the owner, possessor, or person omitting or refusing to comply with the provisions of this section shall, upon conviction, be deemed guilty of a misdemeanor, and after that conviction the court or magistrate having jurisdiction of that offense shall order any peace officer, officer of said society, or officer of an animal shelter or animal regulation department of a public agency, to immediately kill that animal; provided, that this shall not apply to the owner of any old or diseased animal keeping the animal on the owner's premises with proper care.
Ca. Pen. Code § 599e