264 Int. J. Global Environmental Issues, Vol. 1, Nos. 3/4, 2001 Copyright © 2001 Inderscience Enterprises Ltd. The customary international law of transboundary fresh waters Joseph W. Dellapenna Villanova University School of Law, 299 North Spring Mill Road, Garey Hill, Villanova, Pennsylvania 19085-1682, USA E-mail: [email protected] Abstract: Drawing upon the experience of century, nations have constructed a customary international law for transboundary fresh water resources built around the principle of equitable utilisation. The earliest complete formulation of this body of law as the Helsinki Rules on the Uses of International Rivers of the International Law Association of 1966. Like all customary law, this body of international Law retains flexibility by being vague while allowing only for relatively primitive enforcement mechanisms. In an effort to improve things, the United Nations, working initially through the International Law Commission, drafted a convention to codify the customary law. Even before that treaty enters into force, it has become the most cogent summary of the relevant customary international law. Despite certain advances over the customary law in the terms of the treaty, it ultimately fails adequately to integrate the environmental or ecological concerns now emerging in international law into the older body of international water law. This need suggests that a revised Helsinki Rules could serve to complete the unfinished task of adapting international water law to the needs of the twenty-first century. Keywords: Absolute sovereignty; cooperative management; customary international law; International Law Commission; no harm rule; equitable participation; equitable utilisation; riparian state; riverine integrity; transboundary resources; United Nations; water. Reference to this paper should be made as follows: Dellapenna, J.W. (2001) ‘The customary international law of transboundary fresh waters’, Int. J. Global Environmental Issues, Vol. 1, Nos. 3/4, pp.264–305. Biographical notes: Joseph W. Dellapenna is Professor of Law at Villanova University, in Villanova, Pennsylvania, having taught at law schools in the USA and abroad for more than 30 years. In the course of his career, he has practised, taught, and written about managing the water environment, both in the United States and internationally. He made a major contribution to the seven volume treatise Waters And Water Rights, the standard reference work on water law in the USA and has written numerous articles on international water law as well as on other topics. He is the Rapporteur for the Water Resources Committee of the International Law Association with the charge to redraft the Helsinki Rules on transboundary water management in light of developments in international water law and international environmental law over the 35 years since the original Helsinki Rules were approved. He is chair Model Water Code Project of the American Society of Civil Engineers, leading the drafting of two Model Water Codes for the United States, and the drafting of three Model Interstate Water Compacts. In addition to environmental management, Professor Dellapenna's teaching interests have centred on international law and commercial law.The customary international law of transboundary fresh waters 265 1 Introduction Water is unquestionably one of the most important of all the resources that humans depend upon for their survival and thriving, yet it is a resource under increasing stress because of the growth of human populations and changing patterns of use by those populations [1]. All 264 of the world’s largest water river basins – home to about 40 per cent of the world’s population – are shared by more than one nation. [2] This reality requires that mechanisms be devised to assure that these waters are managed cooperatively, if water is not to become a major problem for each nation’s security. [3] To do so requires the creation of a legal structure to govern the state’s cooperation. [4] Without such a structure, competition over water could eventually lead to serious conflict. This article surveys the evolving body of customary international law as a vehicle for addressing the problems of the need for cooperative management of internationally shared fresh water resources, beginning with a discussion of the sources (and nature) of customary international law generally. There follows an analysis of the customary international law of internationally shared fresh water resources and of the recent efforts of the United Nations to codify that body of customary law. The article closes with a discussion of the proposal to redraft the ‘Helsinki Rules’ of the International Law Association [5] in light of all the changes in the customary law in the 30 years since the Helsinki Rules were first approved. 2 Sources of customary international law Until quite recently, international law governed a relatively small and structureless society of states. As late as the end of World War II, the United Nations was created with only 51 members – Switzerland alone chose to stay out of the United Nations, and a handful of defeated Axis states were excluded. The current membership of the United Nations is approaching 200, with at least two significant states (Switzerland and the Republic of China – Taiwan) outside the organisation. The United Nations and other international organisations certainly count as full players (‘legal persons’) in the international legal system. [6] Rapidly proliferating non-governmental and other official and semi-official participants are also now playing a distinct albeit subordinate role. [7] Even natural and artificial persons (people and corporations) are now recognised to some extent as participants in the international legal community. [8] Changes in the United Nations and in other international structures have transformed the international legal system from the relatively simple structure of the past to an increasingly diverse and complex community of actors who too often no longer know much about each other. Furthermore, this growing community of states reflects more sharply differentiated cultural traditions than the smaller group of states prior to World War II; these differences were further accentuated by the division of the world into camps identified by ideological hostilities. This is precisely