Binding the Dogs of War: Japan and the Constitutionalizing of Jus Ad Bellum

Abstract

There is still very little constitutional control over the decision to use armed force, and very limited domestic implementation of the international principles of jus ad bellum, notwithstanding the increasing overlap between international and domestic legal systems and the spread of constitutional democracy. The relationship between constitutional and international law constraints on the use of armed force has a long history. Aspects of constitutional theory, liberal theories of international law, and transnational process theory of international law compliance, suggest that constitutional design could legitimately be used as a pre-commitment device to lock-in jus ad bellum principles, and thereby enhance compliance with that regime of international law.

This paper examines the case of Japan's Constitution to determine the extent to which its war-renouncing provisions incorporated, and are consistent with, international law principles on the use of armed force, and whether the provisions operated to effectively constrain government policy. It concludes that the drafters of the Constitution did incorporate international law principles from jus ad bellum in Art. 9(1), though they also grafted on sui generis prohibitions and rules from jus in bello in Art. 9(2) as well, which complicates the story. The provision was embraced in the ratification process, and became the source of powerful constitutive norms that have helped shape Japan's sense of identity. The paper examines the interpretation of Art. 9, as informed by international law, and concludes that despite deep conflicts over competing narratives and understandings of the provision, the long-standing government interpretation of the provision is consistent with Japan's obligations under the jus ad bellum regime.

In looking at the operation of Art. 9, the paper finds that despite the early use of Art. 9 by governments as a pretext behind which it could pursue desired policy objectives, the provision did operate to effectively constrain government policy in times of apparent crisis. During the Gulf War in particular, Art. 9 effectively bound a straining government to the mast, preventing Japan's participation in the war. It did so not only in its operation as a legal norm, effectively enforced by the Cabinet Legislation Bureau, but also as a powerful constitutive and social norm. As such, the experience of Japan with Art. 9 provides support for the argument that it is feasible to incorporate principles of jus ad bellum into national constitutions, so as to effectively constrain government policy with respect to engaging in armed conflict. Broader arguments as to why that might be desirable, or whether it has served Japan well or ill, are left for another day.

Keywords: jus ad bellum, Japan, armed force, law of armed conflict, Japanese law, constitutional law, international law, pre-commitment theory, legal history, constitutional design, international law compliance

JEL Classification: K33, K1, K30, N45