The doctrine of non-derogation from grants is a principle of the law of England and Wales. As the House of Lords explained in British Leyland Motor Corp. v. Armstrong Patents Co., it states that a seller of realty or goods is not permitted to take any action (such as bringing an infringement action) that will lessen the value to the buyer of the thing sold. United States federal law recognises similar doctrines such as the exhaustion doctrine or doctrine of implied license. A similar effect has also been realised in United States patent law under the doctrine of repair and reconstruction.