This essay provides an interpretation of Article 9 of the Constitution of Japan by illustrating the fact that the provision was originally designed to require Japan to comply with contemporary international law. This essay thus criticizes the traditional interpretation of Japanese constitutional lawyers, who sought to emphasize the distinctiveness of the provision by ignoring its purpose. This essay emphasizes that Article 9 (1) is intended to reinforce the Kellogg ― Briand Pact of 1928 and the Charter of the United Nations of 1945. The Prohibition of “war potential” in Article 9 (2) should be understood in line with the first paragraph. “War” of “war potential” of the second paragraph is in the end the illegal action in contemporary international law. Thus, the second paragraph only indicates the prohibition of the possession of the means to conduct illegal actions. The renunciation of “the right of belligerency of the state” of Article 9 (2) is the provision of non-recognition of the illegal concept in the eyes of international law. Article 9 (2) only repudiates the claim in the wartime Japanese Empire against international law. In conclusion, Article 9 is the declaration of Japan to comply with contemporary international law and cannot be regarded as a provision to renounce the legitimate right of self-defense and the military means to exercise it.