The adoption of the Rome Statute is a significant moment for international criminal law. Before its formulation, the criminal law was governed by the sources mentioned in their statute or Article 38 of the Statute of the International Court of Justice [ICJ Statute]. Custom is one of the important sources within the ICJ Statute. The ad hoc tribunals applied custom and even formulated certain customs. The formulation of custom is considered as against the principle of legality. To avoid such criticism, the State Parties inserted Article 21 in the Rome Statute. The provision clarifies the law which the court can apply. The parties chose not to include custom explicitly. However, the wordings of the provision indicate that the custom is still a source for the court. Apart from the wording of Article 21, other provisions of the Statute give ample scope for the application of custom.
