assume under these agreements as a matter of course. As numerous studies of national implementation of international obligations have shown, however, there is no basis for making such an assumption (Skjaerseth, 2000; Underdal and Hanf, 2000). Implementation typically varies greatly from one regime to another as well as among individual members of the same regime. Not surprisingly, then, the study of factors influencing implementation at the national level has become an important area of emphasis for regime analysis (Underdal, 1998; Victor et al., 1998; Weiss and Jacobson, 1998). What are the key determinants of whether members succeed in implementing the rules of international agreements within their own jurisdictions and whether they accept the outcomes flowing from decision-making procedures operating under the auspices of international regimes? In some cases, this is essentially a matter of political will. Governments can and do sign agreements they have no intention of implementing. Executive branch officials who sign international agreements in good faith may be unable to persuade legislators to pass implementing legislation and allocate the resources needed to operate these arrangements. Furthermore, changes in the composition of governments can bring to power officials who did not participate in the creation of a regime and have little interest in fulfilling obligations undertaken by their predecessors. At the same time, three sets of factors of a more general nature that bear directly on the matter of institutional interplay have emerged as important considerations in this context. For shorthand purposes, we can label these factors competence, compatibility, and capacity.
Competence is a matter of the political and legal authority needed to implement commitments made at the international level. Competence in this sense is largely a function of the constitutional arrangements prevailing within individual countries. In the United States, for example, international conventions do not become legally binding until they are ratified by a two-thirds majority in the Senate. Even then, the U.S. Constitution does not guarantee that commitments embedded in legally binding conventions will always take precedence over domestic laws (Higgins, 1994). As a result, American negotiators in international forums frequently oppose otherwise attractive institutional arrangements on the grounds that there is little prospect that they can survive the pressures arising from domestic legal and political processes. Small wonder, then, that many other countries find the United States a difficult partner when it comes to the creation and implementation of international regimes. In other cases, the problem arises from the allocation of authority between national and subnational units of government in contrast to the separation of powers among the component parts of national governments. In the Canadian confederation, where authority over many issues resides with the provinces in contrast to the federal government, for example, the government in Ottawa lacks the competence to enter into legally binding commitments at the international level regarding numerous issues, without seeking the explicit consent of the individual provinces.13
Compatibility is a matter of the fit or congruence between institutional ar-