Cal. Pen. Code § 597e
Any person who impounds, or causes to be impounded in any animal shelter, any domestic animal, shall supply it during confinement with a sufficient quantity of good and wholesome food and water, and in default thereof, is guilty of a misdemeanor. In case any domestic animal is at any time so impounded and continues to be without necessary food and water for more than 12 consecutive hours, it is lawful for any person, from time to time, as may be deemed necessary, to enter into and upon any animal shelter in which the animal is confined, and supply it with necessary food and water so long as it remains so confined. That person is not liable for the entry and may collect the reasonable cost of the food and water from the owner of the animal, and the animal is subject to enforcement of a money judgment for the reasonable cost of food and water.
Ca. Pen. Code § 597e