The National Treatment Clause, Article 1102 of the North American Free Trade Agreement, protects foreign investors from discrimination, including expropriation of their investments. This national treatment approach - equal treatment of foreign investors and local investors by states - was developed to encourage investment in Europe after the Second World War. Over the course of fifty years, the approach has evolved to provide foreign investors with protections over and above those provided to domestic investors. This article discusses the evolution of national treatment approaches, from affording foreign investors equal treatment to ensuring new investment conditions in international trade.