The Customary International Law Supergame February 23, 200 While the analogy is apparent, we must recognize, of course, that in the cil setting, public communication is possible, as are agreements that at least purport to be binding: treaties. The degree to which agreements may actually constrain behavior is a question for another paper, but we point out that the international legal rule that treatio must be observed (pacta sunt servanda) is itself part of CiL Another, perhaps more important, distinction is that a cartel has certain haracteristics that may differ from any particular CIL setting. That is, in a cartel, the more others adhere to the cartel, the greater the monetary incentives for any particular member to defect. This context is more like a commons problem than like a public good problem. We will discuss some of these distinctions based on payoff structures below iv. International Organization Political scientists and economists working in the field of international organization have made a good deal of progress in anal yzing the problem of international cooperation more generally. In various works, they have examined most of th parameters that we utilize here. This literature has not examined CIL We have structured our model to match most closely the Cil context, rather than attempt to structure a model that would address other international cooperation devices However, we recognize that the question of which device-treaty, CiL or softer law- itself depends on a set of variables. We also recognize that Cil may be understood as a phase in the formalization of law, or in"legalization. CIL is often codified by the nternational law Commission of the united nations and cil often forms the basis for treaty, or of the relationship among these instruments. 28 oi treaties. This article does not present an explanation of choice between custom and There is disagreement between institutionalists and"realists, who claim that states' interests in international relations are characterized by a search for relative gains, rather than absolute gains. These realists reject the possibility of cooperation where it results in relative gains to a competitor. See marc Busch Eric Reinhardt, Nice Strategies in a World of relative Gains: The Problem of Cooperation under Anarchy 37 J CONFL RES 427(1993); Robert Powell, Absolute and Relative Gains in international relations Theory, 85 AM. POL. SCI. REV. 1303(1991); Duncan Snidal, Relative Gains and the Pattern of International Cooperation, 85 AM. POL. SCL. REV. 701(1991) See the special issue of International Organization devoted to the phenomenon of legalization. 54: 3 INT'L ORG. (2000) See Kenneth Abbott Duncan Nidal, Hard and Soft law in International Governance, 54 INT'L ORG. (2000); John K. Setear, Treaty, Custom, Iteration and public Choice,February2004,availableathttpssrn.com/abstract=492604(arguingthatcustom is more attractive to executive branches ). To the extent that cil is less detailed-less specific-than treaty norms, it is amenable to a rules versus standards type of analysis See louis Kaplow, Rules versus Standards: An Economic Analysis, 42 DUKE L.J. 557The Customary International Law Supergame February 23, 2004 9 While the analogy is apparent, we must recognize, of course, that in the CIL setting, public communication is possible, as are agreements that at least purport to be binding: treaties. The degree to which agreements may actually constrain behavior is a question for another paper, but we point out that the international legal rule that treaties must be observed (pacta sunt servanda) is itself part of CIL. Another, perhaps more important, distinction is that a cartel has certain characteristics that may differ from any particular CIL setting. That is, in a cartel, the more others adhere to the cartel, the greater the monetary incentives for any particular member to defect. This context is more like a commons problem than like a public good problem. We will discuss some of these distinctions based on payoff structures below. iv. International Organization Political scientists and economists working in the field of international organization have made a good deal of progress in analyzing the problem of international cooperation more generally. In various works, they have examined most of the parameters that we utilize here. 26 This literature has not examined CIL. We have structured our model to match most closely the CIL context, rather than attempt to structure a model that would address other international cooperation devices. However, we recognize that the question of which device—treaty, CIL or softer law— itself depends on a set of variables. We also recognize that CIL may be understood as a phase in the formalization of law, or in “legalization.” 27 CIL is often codified by the International Law Commission of the United Nations, and CIL often forms the basis for treaties. This article does not present an explanation of choice between custom and treaty, or of the relationship among these instruments. 28 26 There is disagreement between institutionalists and “realists,” who claim that states’ interests in international relations are characterized by a search for relative gains, rather than absolute gains. These realists reject the possibility of cooperation where it results in relative gains to a competitor. See Marc Busch & Eric Reinhardt, Nice Strategies in a World of Relative Gains: The Problem of Cooperation under Anarchy 37 J. CONFL. RES. 427 (1993); Robert Powell, Absolute and Relative Gains in International Relations Theory, 85 AM. POL. SCI. REV. 1303 (1991); Duncan Snidal, Relative Gains and the Pattern of International Cooperation, 85 AM. POL. SCI. REV. 701 (1991). 27 See the special issue of International Organization devoted to the phenomenon of “legalization.” 54:3 INT’L ORG. (2000). 28 See Kenneth Abbott & Duncan Snidal, Hard and Soft Law in International Governance, 54 INT’L ORG. (2000); John K. Setear, Treaty, Custom, Iteration and Public Choice, February 2004, available at http://ssrn.com/abstract=492604 (arguing that custom is more attractive to executive branches). To the extent that CIL is less detailed—less specific—than treaty norms, it is amenable to a rules versus standards type of analysis. See Louis Kaplow, Rules versus Standards: An Economic Analysis, 42 DUKE L.J. 557