The 1959 Abs–Shawcross Draft Convention marks an important year in the early history of international investment law. Many accounts locate the origin of the field in 1959 with the ratification of the first bilateral investment treaty between Germany and Pakistan of the same year. This chapter aims at situating the Abs–Shawcross Draft Convention as a continuation, rather than a beginning, of the development of norms in the field of international investment law. The Draft Convention is one of the L10first to contain provisions that are recognisable to contemporary investment lawyers, but their content is an iteration of the older claims of the principles of acquired rights and the prohibition of unjust enrichment. The chapter demonstrates that the Abs–Shawcross Draft Convention brought the internationalisation of legal authority over concession agreements into formal shape.