Article 11 of the San Francisco Peace Treaty

Japan accepts the judgments of the International Military Tribunal for the Far East and of other Allied War Crimes Courts both within and outside Japan, and will carry out the sentences imposed thereby upon Japanese nationals imprisoned in Japan. The power to grant clemency, to reduce sentences and to parole with respect to such prisoners may not be exercised except on the decision of the Government or Governments which imposed the sentence in each instance, and on recommendation of Japan. In the case of persons sentenced by the International Military Tribunal for the Far East, such power may not be exercised except on the decision of a majority of the Governments represented on the Tribunal, and on the recommendation of Japan.