The present research work is focused on the legal analysis of the relevantarticles of the International Criminal Court’s Statute regarding theobligation of cooperation between States for the punishment of seriouscrimes against humanity and war. Judicial development, starting with adhoc Tribunals and arriving at causes at various stages of proceedings stillongoing at the International Criminal Court, opens the doctrinal and comparativenational debates, seeking to elaborate on specific topics such asrequests for assistance during preliminary investigations, the role of theProsecutor and the non-assistance of some States that for political andnot only reasons impede the development and operation of internationalcriminal justice.