I see two options here. 1) A rent deduction for the loss of use of the backyard. 2) Reporting the conversion to local authorities.
It sounds like an un-permitted conversion for which the city/county could force a take down. If the LL institutes eviction proceeding you can defend by proving it is a retaliatory eviction.
I suggest exhausting all means of communication with the LL in an attempt to come to a compromise before getting the authorities involved.
-Michael R. Juarez Law Office of Juarez and Schaeffer PO Box 16216 San Diego, CA 92105 (619) 804-4327 www.jslaw.org Mike@jslaw.org This posting is provided for “information purposes” only and should not be relied upon as "legal advice." Nothing transmitted from this posting constitutes the establishment of an attorney-client relationship. Applicability of the legal principles discussed here may differ substantially in individual situations or in different jurisdictions.
Your have several options, including an action for forcible entry/forcible detainer. Your landlord has apparently set up illegal units on the land that is part of what you rented. You can also file a complaint with the local code enforcement authorities; doing is so is absolutely privileged. However, THREATENING to do so to get him to take down the barriers could be extortion, which is a felony. You should hire a tenants’ lawyer (not a local landlord lawyer) to represent you.
This is not legal advice and does not create an attorney-client relationship. The information provided is a general statement of the law. Reviewing a case and giving legal advice to a client requires more information than can be exchanged in this format. If you need legal advice, contact an experienced tenants' attorney.