Abstract:
This study deals with the custom in the International law, especially International Criminal Law. On the other hand, it deals with the principle of legality considered as a basic rule in the International Criminal Law and Criminal Law of the country. This study brings to light a problem which indicates that the criminalization, based on custom, is treated as a violation of legality. But the question is whether this violation happens by being out of legality or by amending it according to the nature of International Law which is a part of International Criminal Law, and how this phenomenon affects the judicial guarantees for the accused. This study is based on one assumption supported by the evidence and judicial opinion and the judgments of International Criminal Court. This assumption is related to the legality and the problem of the criminalization based on custom.