Legal Question in Real Estate Law in California

If you and your roommate are both lessees, under the lease (as opposed to you being the lessee and your roommate being a sublessee), then you cannot evict him or her. You would, however, have an action for breach of contract, if you can demonstrate that you and your roommate agreed to share the rent and utilities. Generally, you can go to small claims court for that, if the amount owed is $7500 or less.

While an eviction is normally doen upon complaint of a landlord or purchaser at foreclosure against tenants, subtenants or former owners, by filing and serving an unlawful detainer complaint, I did not notice anything in the law (Code of Civil Procedure sections 1161 et seq.) specifically requiring that the plaintiff be the landlord or buyer at foreclosure rather than an aggrieved cotenant. Arguably, you have standing as an aggrieved party to the lease, or at least, as a third-party beneficiary. So, I cannot say without more research that Mr. Saltzman is absolutely correct, although his answer certainly reflects practical advice. It would be interesting from a theoretical point of view for a tenant to take an unlawful detainer action against a cotenant to court and see whether it could be won (at appeal?).

Needless to say, any kind of legal action against a roommate is going to be a difficult and "trying" experience, and possibly dangerous. Therefore, the easiest route is certainly the best. My advice would also be to consider a small-claims action for money damages, and keep an eye on your valuables while it is in progress! Your roommate may move out rather than endure the suit, but may move out with half your possessions as well.

I usually recommend the Nolo Press book "Everybody's Guide to Small Claims Court in California" to those thinking of taking a case to small claims, or facing having to defend one.