Hersch Lauterpacht and language in the international law of treaty interpretation

The contribution addresses a lesser-known chapter in the history of the rules on the interpretation of treaties: the role played by Hersch Lauterpacht as Rapporteur at the Institut de Droit International on the topic of treaty interpretation. The work of the Institut on this topic was situated within the general effort to progressively develop and codify the rules of international law, a movement itself inspired by the idea of codification that unfolded during the nineteenth century mainly in continental Europe. After the Second World War, Lauterpacht initiated the study of the topic of treaty interpretation both at the Institut and at the International Law Commission (ILC). As Rapporteur at the Institut, Lauterpacht provoked a remarkable controversy by proposing to place the emphasis, in the process of interpretation, on the travaux preparatoires rather than on the text of the treaty. Although the 1956 resolution of the Institut did not follow Lauterpacht in this respect, the work of the Institut nevertheless proved to be a catalytic event leading towards the integrative conception of the rules of interpretation which the ILC developed in the 1960s while preparing the Vienna Convention on the Law of Treaties. The Lauterpacht episode also marked a change of focus with regard to the addressees of the rules of treaty interpretation from intergovernmental interaction towards judicial decision-making.