Legal Question in Landlord & Tenant Law in California

If there are no rent stabilization issues, you might serve a 30- or 60-day notice upon the tenant and the subtenant. Then, if there is no compliance, you might file an unlawful detainer lawsuit.

To put Mr. Cohen's answer in normal english, if you are subject to rent control, you need to look into what limits it places on you. If you are not subject to rent control, and you are on a month-to-month rental, you can terminate the entire tenancy, tenant and sub-tenant, by giving 30-days notice if the original tenant has been there less than a year, or 60-days if the original tenant has been there more than a year. If you are on a longer lease, you can serve a notice to comply with the terms of the lease, which means the subletter must move out. I believe you only need to give three-days, though for illegal subletting it might be 30. In either case, if they do not move out, you have to file an eviction, just like for non-payment of rent.