Legal Question in Real Estate Law in California

In a half hour of searching WestLaw, I found no law, either case law or statute, that clearly governs your situation. In particular, I find nothing that would change ownership of the dog. Therefore, I'd cautiously conclude that you must return the dog to its owner.

There are laws relating to animal-care facilities such as kennels and grooming facilities, and to veterinarians, that give them the right to find a new owner when the owner shows abandonment by being 14 or more days late to pick up an animal, and requiring them to euthanize the animal thereafter, but there are at least three problems in applying those laws (Civil Code sections 1834.5 and to a lesser extent 1834 and 1834.6). First, you are probably not an animal-care facility as defined in the law; second, the facilities are required to post signs as to their policy; and third, it is not clear that the facility itself can become the new owner.

There are other problems as well, concerning a distinction as to whether and when abandonment occurred, which may be different whan a for-hire care facility is concerned and when the pet is in the hands of a friend.