Reciprocity in the Law of Treaties

This chapter considers the role of reciprocity in the international law of treaties. It examines whether or to what extent reciprocity remains fundamental to the law of treaties, and whether reciprocity may have been supplanted by notions of an objective ‘true public international law’ (B. Simma), the effect of which is not contingent on any reciprocal action. The chapter begins by introducing the general concept of reciprocity in relation to the law of treaties. External and internal aspects of reciprocity, as well as positive reciprocity (do ut des) and negative reciprocity (inadimplenti non est adimplendum), are distinguished. In the first major part of the chapter, some instances of reciprocity in the law of treaties are examined. This section examines the role of reciprocity in the making and the interpretation of treaties, as well as in the regime of reservations to treaties and of their termination or suspension. In each case, the analysis also looks for limitations of the effects of reciprocity arising in the modern law of treaties. It is found that such limitations have indeed arisen in some respects. They have arisen above all from the structural quality of some treaties that are not performed between their parties. Of these, the case of the treaties that are not performed in a reciprocal manner between their parties (and that do not exhibit any other form of reciprocal bargain) is the most important. In treaties of this kind, negative reciprocity is absent from the law of treaties, and positive reciprocity (do ut des) seems inferior as an explanation as to why States enter into and perform such treaties to an approach based on community interests. However, this communitarian approach does not spell the end of reciprocity. It remains true that reciprocity supports pacta sunt servanda in the sense that States have to envisage that if they fail to honour a treaty obligation, the same or a related obligation may not be performed with regard to them, and also in the more general sense that States stand to lose international credit if they violate any international obligation. This does not mean that reciprocity establishes pacta sunt servanda as a legal principle. However, reciprocity encourages compliance with international law and gives rise to sanctions for failure to comply. In this regard, substantive aspects of reciprocity are even present in the logic of obligations erga omnes (partes), although negative reciprocity is absent. Finally, it is concluded that reciprocity should not be regarded as a meta-principle of international law. While formal reciprocity is inherent in all treaty law, the positive and negative effects of substantive reciprocity are not so generally valid and so fundamental that reciprocity should be regarded as a meta-principle. This is related to an increase in structures of a true public international law, which serve to limit the role of negative reciprocity, but not of reciprocity in general.