If you're not using it, I think you should sell it to him. It will be easier on both of you. You probably don't want to go through the hassle of a legal fight,

If you're not using it, I think you should sell it to him. It will be easier on both of you. You probably don't want to go through the hassle of a legal fight, and if he's correctly advised, neither does he (especially since he has a nontrivial chance of losing).