For their many thoughtful comments and questions on earlier versions of this paper I wish to thank audiences at the University of North Carolina at Chapel Hill, the University of Manchester, and Washington University in St. Louis, as well as Kim Brownlee, Heather Gert, Zach Hoskins, Terry McConnell, and several anonymous reviewers.

1. Or so many contemporary legal philosophers maintain, and so I will assume in this essay.

2. Of course, agents can have a moral duty to do that which the law requires, independent of the law requiring it. For example, individuals have a moral duty to refrain from murder, and states from genocide, independent of the fact that it is prohibited by law. Even if this is what some commentators mean when they claim that a given state has acted wrongly in violating a particular international legal norm, I suspect that many others believe that the mere illegality of the state’s conduct renders it morally wrong.

3. Exceptions include Posner, Eric A, “Do States Have a Moral Obligation to Obey International Law?” (2003) 55 Stan L Rev 1901 Google Scholar; Buchanan, Allen, Justice, Legitimacy, and Self-Determination: Moral Foundations for International Law (New York: Oxford University Press, 2004)Google Scholar; and Tasioulas, John, “The Legitimacy of International Law” in Besson, Samantha & Tasioulas, John, eds, The Philosophy of International Law (New York: Oxford University Press, 2010).Google Scholar

4. While international organizations and individuals also have international legal duties, I focus here only on states’ duties to obey international law.

5. See Lefkowitz, David, “The Duty to Obey the Law” (2006) 1 Philosophy Compass 571 CrossRefGoogle Scholar [“Duty to Obey”]; Edmundson, William A, “State of the Art: The Duty to Obey the Law” (2004) 10 Legal Theory 215 CrossRefGoogle Scholar.

6. Besides the articles by Hart, Rawls, and Simmons cited below, see also citations in Lefkowitz, , “Duty to Obey” at 587 Google Scholar. For an example of the appeal to the principle of fairness in the context of international law, see Goodin, Robert, “Toward an International Rule of Law: Distinguishing International Law-Breakers from Would-Be Law-Makers” (2005) 9 J of Ethics 225 CrossRefGoogle Scholar.

7. See Lefkowitz, David, “The Sources of International Law: Some Philosophical Reflections” in Besson, Samantha & Tasioulas, John, eds, The Philosophy of International Law (New York: Oxford University Press, 2010)Google Scholar. Some would say that because international law is the product of a consensus among states, it makes no sense to ask whether states have a moral duty to obey it. Rather, their voluntary involvement in international law’s creation necessarily entails a commitment to obey it. This view conflates the conditions for the creation of an international legal obligation with the conditions for a moral obligation to do that which a state has a legal obligation to do (simply because the law requires it).

8. In the future I hope to examine the possibility of justifying international political obligation by appeal to a non-voluntary principle of fairness.

9. Rawls, John, A Theory of Justice (Cambridge, MA: Belknap Press, 1971)Google Scholar; A Simmons, John, Moral Principles and Political Obligations (Princeton, NJ: Princeton University Press, 1979).Google Scholar

10. Hart, HLA, “Are There Any Natural Rights?” (1955) 64 Phil Rev 175 CrossRefGoogle Scholar. Something similar in form to this principle was anticipated in Broad, CD, “On the Function of False Hypotheses in Ethics” (1916) 26 Int’l J of Ethics 377 CrossRefGoogle Scholar.

11. Simmons, supra note 9 at 122-36; see also Rawls, supra note 9 at 111-12.

12. Might a recipient of non-excludable benefits produced by others’ participation in a cooperative scheme be culpable for her ignorance of the fact that she receives the benefits in question, or that they result from others’ cooperation, and so have an obligation to do her fair share in producing them even though she does not meet the knowledge condition? Or suppose that she is aware of these facts, but grossly underestimates the value of the benefits she receives and/or overestimates the cost to her of contributing to the scheme that produces them while making little or no effort to determine if her judgments are correct. Is she then liable to the charge that she treats unfairly those who do contribute, even though she does not willingly receive the benefits? If the agent’s alleged ignorance or her public assessment of the value of the benefits and costs seems deeply unreasonable, we may suspect that she is lying precisely in order to take advantage of us. This possibility raises important questions regarding who bears the burden of proof for demonstrating that someone does or does not have a fair-play obligation to contribute to a given cooperative scheme, especially in contexts where such judgments are employed to justify coercion (e.g., punishment for the failure to contribute one’s fair share). Suppose, however, that the agent’s ignorance or judgment of the net value she will receive if she contributes to the scheme is genuine, though we find it (nearly) inexplicable. In either case, I maintain that this agent has no obligation to contribute her fair share to the operation of the scheme in question. Autonomous creatures enjoy the moral liberty to act on a wide range of bad judgments and decisions, including ones that may undermine the operation of various cooperative schemes that make all who benefit from them better off than in their absence. Crucially, the agent in question does not seek to take advantage of or exploit others’ sacrifices; she is perfectly willing to have the scheme collapse (though we think this willingness foolish on her part), either because she is unaware that it benefits her, or because she mistakenly believes it is not worth the cost to her of contributing to it. Only in those cases where the failure to contribute one’s fair share to a cooperative scheme results necessarily in the violation of others’ basic rights—i.e., fails to respect their status as autonomous agents—do agents act wrongly (and not merely imprudently or stupidly) when they fail to recognize the (moral) importance of the cooperative scheme. In this case, however, the duty to contribute one’s fair share has its basis in the natural, or non-voluntary, duties correlative to those basic rights, and it is a duty an agent has even if she never needs (and never receives) the benefit the scheme produces. Perhaps an account of states’ duties to obey international law can be built on such a foundation, though proponents of a voluntarist version of the principle of fairness frequently argue that individuals can fulfill their (limited) natural duties to others without subjecting themselves to the authority of a legal order. See, for example, Simmons’ argument to this effect in “The Duty to Obey and our Natural Moral Duties” in Christopher Heath Wellman & A Simmons, John, Is There a Duty to Obey the Law? (Cambridge: Cambridge University Press, 2005) at 187–88Google Scholar.

13. A Simmons, John, “Fair Play and Political Obligation: Twenty Years Later” in Justification and Legitimacy (Cambridge: Cambridge University Press, 2001) at 38–42 Google Scholar.

14. Simmons, supra note 9 at 139.

15. Ibid.

16. In the case of international treaties that generate excludable benefits, however, a state might acquire a moral obligation to abide by the terms of the treaty if it tries to get the benefits the treaty provides, regardless of whether it thinks those benefits worth limiting its liberty in the ways the treaty specifies. Interestingly, this might produce a situation in which a state has a moral, but not a legal, obligation to abide by certain treaty norms.

17. States do enjoy legal personality, of course, and usually enjoy political autonomy, but these are not obviously equivalent to moral personhood or moral autonomy.

18. In this respect it mirrors Nozick’s objection to the principle of fairness.

19. Wellman, Christopher Heath, A Theory of Secession: The Case for Political Self-Determination (Cambridge: Cambridge University Press, 2005) at 47, 50–51 CrossRefGoogle Scholar.

20. As in the case of individuals, a group’s claim to non-interference in its pursuit of a particular way of life is limited by certain natural (i.e., non-voluntary) duties it has to other groups and individuals.

21. For a defense of an individualist (or reductivist) account of group political self-determination, see Lefkowitz, David, ‘On the Foundation of Rights to Political Self-Determination: Secession, Non-Intervention, and Democratic Governance” (2008) 39 J Social Phil 492 CrossRefGoogle Scholar.

22. As the author of a recent textbook on international law puts the point, “although the protagonists of international life are States as legal entities or corporate structures, of course they can only operate through individuals, who do not act on their own account but as State officials, as the tools of the structures to which they belong” ( Cassese, Antonio, International Law, 2d ed (New York: Oxford University Press, 2005) at 4 Google Scholar).

23. International law already confronts a similar difficulty in the case of opinio juris, a condition on the existence (and some say creation) of customary international law, according to which states must act from the belief that international law requires that they so act. The obscurity of state’s motivations for acting as they do has led some international legal scholars to advocate for the abandonment of opinio juris, but this leads to insuperable problems in explaining the normativity of customary international law. For discussion, see Lefkowitz, David, “(Dis)solving the Chronological Paradox in Customary International Law: A Hartian Approach” (2008) 21 Can JL & Jur 129 Google Scholar.

24. Matthew Lister makes some of these same points in his defence of states’ right to withdraw their consent to international legal norms (except for jus cogens norms). See Lister, , ‘The Legitimating Role of Consent in International Law’ Chicago J Int’l L [forthcoming in 2011]Google Scholar.

25. Even if state officials do view certain international legal norms, such as those outlawing trade in certain narcotics, as imposing costs on them, the important question is whether they think the benefits provided by the international legal order are worth these costs. That is, do states believe that, on the whole, they benefit more from the opportunities forgone by other states as a result of those states’ obedience to international law than they pay in terms of the opportunities forgone as a result of their own compliance with international law? Answering this question may seem to require that we determine the baseline an agent ought to use when calculating the costs and benefits of participation in a cooperative scheme. But in fact, it does not matter how the baseline question is resolved, since what acceptance of benefits requires is that the relevant agent believes that he (or it) receives a net benefit from the cooperative scheme, and not the veracity of this belief. Thus regardless of what baseline an agent ought to use to determine whether a given cooperative scheme provides him with a net benefit, what matters is whether the agent believes a net benefit exists, whatever baseline he employs.

26. Note, however, that in light of differences in the size and sophistication of their diplomatic corps, states vary in their actual ability to persistently object to evolving customary legal norms.

27. Simmons, supra note 13 at 39-40.

28. Some commentators on earlier versions of this paper have argued that international affairs are characterized as much by coercion as by cooperation. Even if this is true, it need not undermine the argument that states can have a fair-play duty to obey international law. In particular, where coercion is used to enforce the law, it contributes to the justification for such a duty by providing assurance to those who cooperate that they will not be taken advantage of.

29. Simmons, supra note 13 at 40.

30. Ibid at 41.

31. Thus the oft-lamented “horizontal” nature of the international legal order may turn out to be morally advantageous in some respects.

32. Jus cogens norms—international legal norms from which states may not derogate—constitute a small exception to this essentially voluntarist picture of international legal obligation. I attach the qualifier ‘formally’ to the statement in the text because it is arguable that in practice some states lack the resources to keep abreast of all the developing international legal norms, or to persistently object to them.

33. Simmons, supra note 13 at 39.

34. If the argument set out in the last three paragraphs is correct, then it also undermines one of the arguments Simmons offers in support of the conclusion that the principle of fairness cannot justify a duty to obey domestic law—namely that the legal order partly constitutive of a modern state does not constitute a genuine cooperative scheme.

35. A given political community may have other moral reasons, or prudential ones, for repaying money borrowed when that community was organized as a morally illegitimate state.

36. See Lefkowitz, David, “A Contractualist Defense of Democratic Authority” (2005) 18 Ratio Juris 346 CrossRefGoogle Scholar. In my view, the rights to political self-determination and to a liberal-democratic form of governance are both grounded in respect for individuals as autonomous agents, i.e., reasonable and rational creatures.

37. One additional complicating feature of the international legal order must be noted, namely the possible (or in some cases, probable) injustice of particular international legal rules. It seems implausible to claim that an agent can have a fair-play obligation to contribute to a cooperative scheme in a substantively unjust manner; a member of the Mafia cannot acquire a fair-play obligation to commit murder because it constitutes doing his fair share in a cooperative scheme. Likewise even a legitimate state cannot acquire a fair-play obligation to comply with the demands of a clearly unjust treaty (or the clearly unjust provisions of a treaty), even if it goes through all of the steps necessary to create a binding legal obligation to do so.