Legal Question in Real Estate Law in California

The one that did illegal additions is generally liable, but all that means is that you get to sue them for your damages, IF the statute of limitations hasn't run, and IF you can locate them, and IF they have any assets and income from which you could collect a judgment. Suing them doesn't slow or stop the govt from pursuing action against you to fix or tear down. However, you can fight that process through legal counsel, and possibly negotiate some resolution. It may be as simple as paying a penalty and getting permits. You should also make a claim upon you title insurance and homeowners insurance policies, if possible. Consult with local counsel.