How do states join the International Criminal Court?: the implementation of the Rome Statute in Japan

Against the background of Japan's long-anticipated implementation of the Rome Statute of the International Criminal Court in 2007, this article analyses the legislative implications of treaty accession. One of the causes of the accession delay in Japan - nearly 10 years passed between the government's participation in the adoption of the Rome Statute and its implementation thereof - was the challenge of aligning the conflicting imperatives of domestic and international law. This article delineates these conflicting imperatives, reconstructing the deliberations over procedural and substantive law that attended the drafting of implementing legislation in Japan. We demonstrate in our analysis that unlike most other countries who joined the ICC community as States Parties, Japan had to overcome particularly formidable constitutional and legislative hurdles before membership in the permanent international court could become a possibility. Among other things, the implementation of the Rome Statute required a renegotiation, in key respects, of the fundamental principle upon which Japan's post-World War II foreign and domestic policy rested, namely the renunciation of war and the culture of antimilitarism that is enshrined in Article 9 of the Constitution of Japan.