International Commitments of Japan’s Prefectures with Foreign States: Empirical Patterns, Authority, and Legal Nature

Authors

• Yuhei Matsuyama

First Page

321

Abstract

Under international law, sovereign states are the primary subjects of rights and obligations and possess the authority to conclude treaties. Domestic constitutions typically allocate foreign affairs powers to national governments. Nonetheless, subnational governments—including prefectures—regularly engage in international activities. In some federal systems, constituent units are expressly authorized by their constitutions to conclude international agreements. By contrast, the Constitution of Japan vests foreign affairs authority exclusively in the national executive and is silent on the authority of prefectural governments. This Article uncovers and analyzes approximately 180 previously unexamined international commitments concluded by Japanese prefectural governments with foreign states, identified through information disclosure requests. It provides descriptive empirical findings on foreign partners, subject matter, and the legal features of the commitments, including terminology, compliance provisions, dispute-settlement mechanisms, termination clauses, and statements on legally binding nature. Building on these findings, the Article evaluates prefectural authority to conclude such commitments and assesses their legal nature under international law and Japanese domestic law. It shows that prefectures lack treaty-making competence and that most commitments are non-binding instruments, although a limited number exhibit binding contractual characteristics. The Article thereby clarifies an underexamined dimension of Japan’s constitutional and international legal order.

Recommended Citation

Yuhei Matsuyama, International Commitments of Japan’s Prefectures with Foreign States: Empirical Patterns, Authority, and Legal Nature, 51 Brook. J. Int'l L. 321 (2026).
Available at: https://brooklynworks.brooklaw.edu/bjil/vol51/iss2/2