Scholars of international law compliance have not identified an approach that covers the full gamut of international norms. Realist, rationalist and constructivists explain certain facets of the compliance puzzle but fall short in many areas.I propose a comprehensive theory of international law compliance that focuses on the structure of the agreements by distinguishing between international promises and international pledges. Starting with the premise that all international law is horizontal and that compliance is likely to be weak, I argue that compliance will be the greatest with respect to promises rather than pledges. Promises - like contracts - typically involve a reciprocal exchange of benefits or withholding of sanctions that are amenable to measurement. Such agreements are usually high on the legalization scale (precision, obligation, delegation). They also affect reputations far more. Cheating will still occur, but it will be both more subtle and more rare. Pledges, on the other hand, involve commitments of internal reform that are not reciprocal and non-compliance has few externalities. States enter into these agreements for domestic purposes, primarily, or to misrepresent themselves to outside audiences. The commitments naturally score low on the legalization scale and compliance is likely to be superficial unless driven by domestic forces. ..PAT.-Unpublished Manuscript [ABSTRACT FROM AUTHOR]