Legal Question in Real Estate Law in California

It probably depends upon the person's original status as an occupant ....... was he a tenant, a guest, a lodger, or perhaps an employee? Also, have you communicated with him? How? Just asked him to leave, or given some kind of formal written notice? There are too many additional facts needed to give an answer taking into account both parties' possible rights here. I'd suggest getting local advice from a local attorney or maybe even a tenants' rights organization. More likely than not, he was/is legally a "guest" and can be turned into a mere trespasser by giving notice to leave, after which the police or sheriff can be brought in, but it's much safer to be sure.