What you are describing could probably be construed to be Adverse Possession by a motivated lawyer. In this case you would actually now own the tree, and thus the previous owner would not be able to sell your tree in the first place. https://en.wikipedia.org/wiki/Adverse_possession "Adverse possession is a method of acquiring title to real property by possession for a statutory period under certain conditions, viz: proof of non-permissive use which is actual, open and notorious, exclusive, adverse, and continuous for the statutory period."