Legal Question in Real Estate Law in California

What sort of right, if any, does the unwanted occupant assert? Is he/she a spouse, child, or claim to be a tenant or co-owner? Each of these may require a different approach, although probably in court with a lawyer or via an eviction process.. If the person has no claim and is merely an overstaying guest or a common trespasser, maybe the police or sheriff could handle it. There's no single answer that fits all situations.