If international regimes did not exist, they would surely have to be invented.
International regimes represent an integral part of globalisation and according to Little, the number of regimes increases steadily. Moreover, regimes account for a great deal of everyday convenience, ranging from seemingly simple practices like sending a letter abroad to the most complex economic interactions. In fact, “there is now no area of international intercourse devoid of regimes, where states are not circumscribed, to some extend or other, by the existence of mutually accepted sets of rules.”
Undisputedly, the realist paradigm dominates any debate in International Relations. “Realism has dominated international relations theory at least since World War II.” It is therefore obvious to begin the search for an explanation for the growing number of international regimes and states’ willingness to participate in them within realism itself. Yet, how can realism, that regards states as sovereign units concerned primarily with their own security and survival in an anarchic international system, account for extensive cooperation in regimes?
In order to assess whether realism provides a suitable explanation for the obvious success of regimes, this essay shall compare the realist approach to the neo-liberal account of regimes. Although the existence of international regimes is acknowledged by neo-liberals and realists, the two groups have competing theories about the formation of those regimes.
Having looked at these two different approaches to explain the existence of regimes, this essay shall argue that the notion of ‘self-interest’ is, perhaps surprisingly, the very reason why states would want to participate in regimes and not at all an impediment, as the question suggests. However, the realist explanation of regimes does not stress the importance of states’ self-interest as a cause for regime formation. It is the neo-liberal regime theory that holds that self-interest is a motive for states to cooperate in regimes. Hence, this essay will conclude that the realist theory does not provide an accurate account for the creation of regimes and their durability.
Yet, before comparing the two major theories about international regimes, it is necessary to define what constitutes a regime. Krasner has given the most accepted definition of regimes, which shall be used in this essay:
Regimes can be defined as implicit or explicit principles, norms, rules, and decision-making procedures around which actors’ expectations converge in a given area of international relations. Principles are beliefs of fact, causation, and rectitude. Norms are standards of behaviour defined in terms of rights and obligations. Rules are specific prescriptions or proscriptions for action. Decision-making procedures are prevailing practices for making and implementing collective choice.
Krasner’s definition leaves no doubt that the idea of a regime goes beyond that of a simple set of rules because a regime also provides ‘decision-making procedures’, which requires “quite a high level of institutionalization.” Institutionalisation is commonly seen as a feature of organisations and therefore one might be tempted to equate organisations and regimes. However, although organisations as well as regimes are indeed international institutions, they are far from alike.
Perhaps the most fundamental difference between regimes and organizations –both of which can be seen as representing a type of international institution– lies in the fact that regimes […] do not possess the capacity to act, whereas organizations can respond to events […].
 Robert O. Keohane, “The Demand for International Regimes”, in: Robert O. Keohane, International Institutions and State Power, Westview, London, 1989, p.125
 Richard Little, “International Regimes”, in: John Bayliss and Steve Smith (eds.), The Globalization of World Politics: An Introduction to International Relations, Oxford University Press, Oxford, 1997, p.234
 ibid., p.232
 Joseph M. Grieco, “Anarchy and the Limits of Cooperation: A Realist Critique of the Newest Liberal Internationalism”, in: International Organization, Vol. 42, No. 3, 1988, p.485
 Although not only does classical realism not explain the existence of regimes but denies its workability, and only neo-realism does acknowledge and attempts to explain the existence of regimes, the literature rarely makes reference to this distinction. The term ‘realism’ is thus used in this essay throughout.
 This essay acknowledges that “liberal co-operation theory and realism are not the only approaches for understanding international regimes, even if they are the most prominent.” (Stephen D. Krasner, “Sovereignty, Regimes, and Human Rights”, in: Volker Rittberger (ed.), Regime Theory and International Relations, Clarendon Press, Oxford, 1993, p.141) However, there will be no space here to discuss any other regime theory.
 Stephen D. Krasner, “Structural Causes and Regime Consequences: Regimes as Intervening Variables”, in: International Organization, Vol. 36, No. 2, 1982, p.186
 Little, op.cit., p.234
 Andreas Hasenclever and Peter Mayer and Volker Rittberger, Theories of international regimes, Cambridge University Press, Cambridge, 1997, p.10f