The Customary International Law Supergame February 23, 2004 This article draws on four semi-autonomous literatures. First, as noted above there is an emerging rationalist, law and economics-based literature of CIL. The leading work in this area is by goldsmith and Posner, but there are other important contributions Second, this article draws on a burgeoning literature on social norms in the law, although social norms are studied by all manner of social scientists. Third, this article draws from he economics field of industrial organization analogies to game theory-based insights about collusion among competitors in markets. Fourth, this article draws from the political science literature of international organization, which has addressed in detail the game theoretic analysis of cooperation among groups of states. Law and economics of cil Goldsmith and Posner provide a game theoretic analysis of CIL. They examine a variety of CIL circumstances, and argue that they can be categorized into four game types: (1)coincidence of interest, (ii) coercion, (iii) bilateral cooperation, and (iv coordination. This is a useful exercise. as it invites us to consider the motivation of states, and the degree to which Cil affects behavior. In the perhaps hypothetical cases of pure coincidence of interest and coercion, Goldsmith and Posner are correct that there can be no opinio juris, and that law does little work. This is not new to Cil doctrine, but it is useful to emphasize. It is also useful to emphasize that Goldsmith and Posner seem to assume a purity of motivation that may not exist in the real world Goldsmith and Posner suggest that many instances of observed CIL may be understood in terms of bilateral cooperation along the lines of a bilateral prisoner's dilemma game. They then argue that"Although game theory does not rule out the possibility of n-state cooperation, the assumptions required for such an outcome are quite strong and usually unrealistic. For this reason, we doubt the utility of n-player prisoner's dilemmas as an explanation for multilateral or universal behavioral regularities. Their views with respect to coordination games are similar. In addition to developing this theoretical perspective, Goldsmith and Posner examine several examples of CIL. The areas they consider are neutrality, diplomatic immunity and maritime jurisdiction. They find that in these areas, states were motivated by coincidence of interest, coercion or a bilateral reciprocity along the lines of the prisoners dilemma. They conclude that if state behavior can be explained by coincidence of interest or coercion, or any other self-interested-motivation, then neither opinio juris nor Cil does any motivational work Social norms We might ask, however, whether the cil problem is different in structure from the social norms context and whether if social norms can affect behavior CIL can as Goldsmith Posner 1999, supra note 2, at 1130The Customary International Law Supergame February 23, 2004 5 This article draws on four semi-autonomous literatures. First, as noted above, there is an emerging rationalist, law and economics-based literature of CIL. The leading work in this area is by Goldsmith and Posner, but there are other important contributions. Second, this article draws on a burgeoning literature on social norms in the law, although social norms are studied by all manner of social scientists. Third, this article draws from the economics field of industrial organization analogies to game theory-based insights about collusion among competitors in markets. Fourth, this article draws from the political science literature of international organization, which has addressed in detail the game theoretic analysis of cooperation among groups of states. i. Law and Economics of CIL Goldsmith and Posner provide a game theoretic analysis of CIL. They examine a variety of CIL circumstances, and argue that they can be categorized into four game types: (i) coincidence of interest, (ii) coercion, (iii) bilateral cooperation, and (iv) coordination. This is a useful exercise, as it invites us to consider the motivation of states, and the degree to which CIL affects behavior. In the perhaps hypothetical cases of pure coincidence of interest and coercion, Goldsmith and Posner are correct that there can be no opinio juris, and that law does little work. This is not new to CIL doctrine, but it is useful to emphasize. It is also useful to emphasize that Goldsmith and Posner seem to assume a purity of motivation that may not exist in the real world. Goldsmith and Posner suggest that many instances of observed CIL may be understood in terms of bilateral cooperation along the lines of a bilateral prisoner’s dilemma game. They then argue that “Although game theory does not rule out the possibility of n-state cooperation, the assumptions required for such an outcome are quite strong and usually unrealistic. For this reason, we doubt the utility of n-player prisoner's dilemmas as an explanation for multilateral or ‘universal’ behavioral regularities.” 9 Their views with respect to coordination games are similar. In addition to developing this theoretical perspective, Goldsmith and Posner examine several examples of CIL. The areas they consider are neutrality, diplomatic immunity and maritime jurisdiction. They find that in these areas, states were motivated by coincidence of interest, coercion or a bilateral reciprocity along the lines of the prisoner’s dilemma. They conclude that if state behavior can be explained by coincidence of interest or coercion, or any other self-interested-motivation, then neither opinio juris nor CIL does any motivational work. ii. Social Norms We might ask, however, whether the CIL problem is different in structure from the social norms context, and whether if social norms can affect behavior, CIL can as 9 Goldsmith & Posner 1999, supra note 2, at 1130