Existential Threats and Deterrence: Japan's Legal Pathway to Enhanced Collective Security in Asia

With the Japanese Cabinet’s decision in December 2022 to comprehensively upgrade Japan’s security posture, and its rapid build-up of its defense capabilities, Japan’s role in Asia’s security architecture has been undergoing a fundamental shift. This article places Japan’s 2015 Peace and Security Legislation in the context of the U.N. collective security system and argues that its most significant achievement has been to expand Japan’s power to engage more proactively in the Asian collective security order. To date, commentators have focused on the legislation’s role in expanding the Japanese constitution’s limitations on the use of force to permit collective self-defense. This article argues that the legislation’s true significance lies in Japan’s strengthened deterrence capabilities resulting from an evolution away from its narrow focus on survival threats as a justification for permissible uses of force (a subject of constitutional interpretation), to broader legal justifications for the use of arms to counter lower order threats (a subject of legislative action). These enhanced capabilities have permitted Japan to undertake initiatives to build a new security architecture in Asia based on a significantly strengthened U.S. alliance and supplemental “minilateral” groupings. However, as deterrence activities grow, the line between “deterrence” and “survival” may start to blur, potentially taking the debates about permitted uses of force in new directions. The separate histories of the U.S. and Japan’s engagement with collective security suggest the directions in which these debates may lead.