First: Find out why your unit is not registered. If it is not registered because it was built without permits and thus cannot be registered, you can legally stop paying rent. You then can sue the landlord for three times his illegal overcharges. You should not have trouble finding a plaintiff's -tenant lawyer to handle this suit on a contingency basis. Do not go to Small Claims Court because most judges are not familiar and are not interested in learning about Los Angeles Rent Control Law.
Second: If your rental unit is legal, all the landlord has to do to collect the back and current rent is register the unit. At that time your will have no cause of action against the landlord. Thus, if you stop paying the rent, the landlord will merely register the unit and then give you a Three-Day Notice to Pay or Quit. If you do not pay, he will gladly evict a "problem tenant."
I disagree somewhat with my colleague. Under the City of Los Angeles Rent Stabilization Ordinance, late registered does not retroactively validate collection of the old rent. It only permits collection of rent going forward. If you are concerned about being evicted for non-payment of rent, you can file a complaint with the Los Angeles Housing Department, which can issue a notice that the landlord cannot collect rent until it is registered and will be a clear defense to an unlawful detainer,
Finally, treble damages require proof that the landlord intentionally collected rent illegally, which is not simple or easy to prove.