In the best traditions of scholarly debate Professor John Norton Moore has taken sharp and fundamental issue with the legal analysis of the United States' role in the Viet Nam war that I outlined in a previous issue of the Yale Law Journal. Professor Moore has not persuaded me either that my approach is “simplistic” or that its application to Viet Nam is “unsound,” but he has identified weaknesses and incompletenesses in my earlier formulation. In addition, he has developed an alternative legal framework for assessing foreign intervention in violent struggles for the control of a national society. My objective in responding is to clarify the contending world order positions that each of us espouses. Although Professor Moore affirms and I deny the legality of the United States' military role in Viet Nam, the main center of intellectual gravity in this debate is less passing judgment on the grand legal issue of American presence (at this stage, a legalistic exercise) than it is assessing the policy implications of the Viet Nam precedent for the future of international legal order.

Professor Moore and I agree that international law can serve as a significant source of guidance to the national policy-maker in the area of war and peace. International law implies a process of decision incorporating perspectives that tend to be left out of account when government officials develop national policies solely by considering capabilities, strategies, and current foreign policy goals that are designed to maximize the short-run “national advantage.” International law contains rules and standards rooted in the cosmopolitan tradition of a community of nations, whereas foreign policy tends to be rooted in the more particularistic traditions of each state. The future of world legal order may depend to a great degree on the extent to which the decision process relied upon in principal states to form foreign policy can come increasingly to incorporate more cosmopolitan perspectives.

International law has itself evolved through a process of decision in which national policies governing the appropriate uses of military power have been clarified by the assertion of adverse national claims buttressed by supporting explanations and rationale. This process is especially germane whenever the relevance of the rules to the claims of states is challenged on a legal basis, as it has been since the outset of major United States involvement in Viet Nam.