Chapter VIII
Execution of Decision of the International Court
Article 46. Execution of a deprivation of liberty sentence
4. If the convict submits a motion for his release parole, pardon, appeal or renewal of proceedings due to newly discovered circumstances, as appropriate state authority shall immediately forward such a motion together with other necessary documentation to the International Court. Only the International Court shall have the power to reduce the length of imprisonment or mitigate the sentence in any manner.
Non-modification of sentence by State
Periodical review by ICC regarding reduction of sentence
EDIT.