Legal Question in Landlord & Tenant Law in California

I am not sure you have grounds to terminate the lease yet, but you certainly can demand removal of the equipment and plants. First off, the form has a no-modifications without consent provision. You consented to an office not a marijuana growing facility. Second, you have a no illegal activity clause. Although legal under state law, it is still a federal crime to grow marijuana for distribution, and it could subject your land owner, and even you personally, to prosecution and penalties up to and including seizure of the land, if you allow it to continue. You should issue a formal written three-day notice to remove all equipment and uses of the premises that are not in conformance with the lease. If they fail or refuse to comply you will then be able to file an unlawful detainer case to terminate the lease and remove them from the premises.

You should also check with the local police, without revealing names, whether the documents from the collective actually allow him, as opposed to the collective, to do what he is doing.