Is it legal in a commercial lease in California for the lessor to have the option to keep the lessee's cabinetry and sinks in a build out or require them to take them out after the lease term ends and to notify them 30 days prior to the expiration of the lease which it will be?
We call those "tenant improvements" or TI's. It is legal in California for a lease to specify who owns tenant improvements, and when the tenant can or cannot remove tenant improvements.
Unless the lease required the landlord to exercise its option 30 days prior to expiration, no such obligation to make an election would exist.