The Customary International Law Supergame 19 February 23, 2004 The skepticism of prior work regarding the possibility for non-defecting multilateral equilibria even in non-cooperative games is misplaced. The industrial organization literature recognizes important possibilities for cooperative outcomes in multilateral settings. The same seems to apply to the cil game The number of players in any particular instance of the CIl game will vary. The maximum number of players is the total number of states in the world, although even this may ignore some detail. There are other players besides states, including sub-state governmental entities, international government entities, non-government organizations and individuals, so we have a potentially unlimited universe. In this paper, we assume billiard ball"states. While we recognize that we lose nuance by doing this, we are rying to work with a simple model that assumes that states have unitary preferences. Even limiting our universe to states, with approximately 200 in the world, there would seem to be a significant problem of obtaining information about positions and practices, as well as coordination. However, while states may possess formal sovereign equality, they are not substantively equal, and their participation in the cil formation process is not homogeneous. 7 Oscar Schachter writes that "As a historical fact, the great body of cil was made by remarkably few States. Only the States with navies-perhaps 3 or 4made most of the law of the sea. Military power, exercised on land and sea, shaped the customary law of war and, to a large degree, the customary rules on territorial rights and principles of State responsibility. This leaves us with a game in which the number of players varies, depending on the degree of implication of their interests, and depending on their ability to affect outcomes. In this game, players are heterogeneous across a number of parameters, including interest and power, and as will be seen below, discount factors. In this sense, we may think of powerful states engaging in the cil formation and maintenance game as exerting power through the articulation, formation and maintenance of CIL rules Schachter wrote of general CIL, but it is also possible to have regional or other plurilateral CIL. 59 See Lisa l. Martin, The Rational State Choice of Multilateralism, in MULTILATERALISM MATTERS 91, 99 John G. Ruggie, ed 1993)(suggesting techniques, including delegation as in the Security Council, of reducing the effective number of pl Oscar Schachter, New Custom: Power, Opinio Juris, and Contrary Practice, in Je Makarczyk, ed, THEORY OF INTERNATIONAL LAW AT THE THRESHOLD OF THE 2/ Jerzy CENTURY: ESSAYS IN HONOUR OF KRZYSZTOF SKUBISZEWSK, 531, 536(Kluwer 1996) See also Mendelson, supra note 8, at 194, 215, 225(in the past, " civilized"states were considered sufficient, and the applicable group of states need not be geographical constrained) See Asylum Case(haya de la Torre), 1950 I.C.J. 266; Case Concerning the Right of Passage Over Indian Territory, 1960ICJ. 6. C. MALCOLM N SHAW, INTERNATIONALThe Customary International Law Supergame February 23, 2004 19 The skepticism of prior work regarding the possibility for non-defecting multilateral equilibria even in non-cooperative games is misplaced. The industrial organization literature recognizes important possibilities for cooperative outcomes in multilateral settings. The same seems to apply to the CIL game. The number of players in any particular instance of the CIL game will vary. The maximum number of players is the total number of states in the world, although even this may ignore some detail. There are other players besides states, including sub-state governmental entities, international government entities, non-government organizations and individuals, so we have a potentially unlimited universe. In this paper, we assume “billiard ball” states. While we recognize that we lose nuance by doing this, we are trying to work with a simple model that assumes that states have unitary preferences. Even limiting our universe to states, with approximately 200 in the world, there would seem to be a significant problem of obtaining information about positions and practices, as well as coordination. However, while states may possess formal sovereign equality, they are not substantively equal, and their participation in the CIL formation process is not homogeneous. 57 Oscar Schachter writes that “As a historical fact, the great body of CIL was made by remarkably few States. Only the States with navies—perhaps 3 or 4—made most of the law of the sea. Military power, exercised on land and sea, shaped the customary law of war and, to a large degree, the customary rules on territorial rights and principles of State responsibility.” 58 This leaves us with a game in which the number of players varies, depending on the degree of implication of their interests, and depending on their ability to affect outcomes. In this game, players are heterogeneous across a number of parameters, including interest and power, and as will be seen below, discount factors. In this sense, we may think of powerful states engaging in the CIL formation and maintenance game as exerting power through the articulation, formation and maintenance of CIL rules. Schachter wrote of general CIL, but it is also possible to have regional or other plurilateral CIL. 59 57 See Lisa L. Martin, The Rational State Choice of Multilateralism, in MULTILATERALISM MATTERS 91, 99 (John G. Ruggie, ed. 1993) (suggesting techniques, including delegation as in the Security Council, of reducing the effective number of players). 58 Oscar Schachter, New Custom: Power, Opinio Juris, and Contrary Practice, in Jerzy Makarczyk, ed., THEORY OF INTERNATIONAL LAW AT THE THRESHOLD OF THE 21 ST CENTURY: ESSAYS IN HONOUR OF KRZYSZTOF SKUBISZEWSK, 531, 536 (Kluwer 1996). See also Mendelson, supra note 8, at 194, 215, 225 (in the past, “civilized” states were considered sufficient, and the applicable group of states need not be geographically constrained). 59 See Asylum Case (Haya de la Torre), 1950 I.C.J. 266; Case Concerning the Right of Passage Over Indian Territory, 1960 I.C.J. 6. Cf. MALCOLM N. SHAW, INTERNATIONAL