Legal Question in Real Estate Law in California

In some cases, yes. Real-property law includes an "agreed boundary doctrine". When the true location of a boundary line between two properties is uncertain, the coterminous owners can establish the boundary between them by agreement. The agreement need not be express or in writing, but can be implied by the facts and circumstances. These can include existence of a fence and general acceptance of the fence as an indicator of where they believe the property line is located. Also, there must have been bona fide uncertainty by both neighbors as to where the true property line was located, and some facts indicating that both of them at least tacitly recognized the fence as the boundary, or a reasonable approximation thereof. There are a few other intricacies of "agreed boundary doctrine", so if it becomes an issue, one or both parties should see a local real-estate attorney for a more in-depth look into whether this doctrine applies to their situation.