Speak softly and carry a big stick. President Theodore Roosevelt (1901)
A measure of cooperation was sustained by a self-enforcing agreement in Chapter 7 only because signatories were assumed to comply fully with the agreement. If we were to drop this assumption, cooperation would unravel. The reason is that the collectively rational abatement level prescribed by the treaty is not individually rational. Each signatory could thus gain by reducing its abatement—even if only by a little—while none of the other signatories would have the opportunity to punish any such deviation. Given the chance, every signatory would thus deviate. Once we abandon the assumption of full compliance in the stage game, cooperation falls apart.
Of course, the analysis of Chapter 7 did rely on individual rationality as regards participation—the decision by signatories to remain within a treaty (as well as the decision by non-signatories to stay out). So Chapter 7 did not assume that states would comply with just any agreement. It merely assumed that signatories would comply with the agreements from which signatories did not want to withdraw unilaterally (and to which non-signatories did not want to accede unilaterally). This may seem a subtle distinction but it will prove important to the conclusions reached in this book about compliance and participation.
This chapter investigates the incentives for compliance, and the mechanisms needed to enforce compliance. It constructs a different kind of model from the one developed in Chapter 7 , a model based on repeated interactions in which enforcement is endogenous. Nonetheless, the model developed here is compatible with the one developed previously. Indeed, the main conclusions of this chapter derive from a comparison of the results for the two models.
As a practical matter, the assumption of full compliance adopted in Chapter 7 might seem innocent enough. States do tend to comply fully with their treaty obligations. Indeed, legal experts Abram Chayes and Antonia Chayes (1991 : 311) introduce their analysis on compliance by noting that “international lawyers and others familiar with the operations of international treaties take for granted that most states comply