Defines the concepts of direct and indirect expropriation and reviews the variety of measures that can constitute an expropriation. Discusses what economic rights and interests may constitute an object of a taking. Reviews in detail the conditions for an expropriation to be lawful, namely public purpose, non-discrimination, due process and payment of compensation. Discusses the differences between compensation for a lawful expropriation and reparation for unlawful expropriations, as well as the question of valuation of investments. Offers options that policymakers and negotiators may wish to consider.