Legal Question in Real Estate Law in California

I think you should find a local lawyer who specializes in real estate matters, particularly boundary and easement disputes. Based upon the limited information given, this sounds like a rather common situation ....... fence built not on the boundary line, but neighbors at one time thought is WAS on the boundary. Who wins these cases depends upon how long the situation has existed, what use each neighbor has made of the disputed land in the meantime, and some other facts. Also, after you have an initial face-to-face meeting with a lawyer, you'll need to decide whether the value of the land and your chances of winning make it worthwhile to hire the lawyer and go to court, or whether you'd be better off negotiating some kind of out of court settlement with the neighbor. If you do that, be sure the agreement gets written up and recorded.