This article argues that the drafters of the Rome Statute, in their desire to hem in the interpretative mandate granted to the judges of the ICC, have created an unfortunate relationship between the sources of international law in the Court. This has come about because of the creation of a hierarchy of sources in Article 21 of the Statute, which does not comport with general international law or the rules of treaty interpretation. Through an analysis of the use of the various sources of international law in the Al-Bashir case, the article shows how this can distort the definitions of international crimes. It also raises the specter of fragmentation within international criminal law, where crimes such as genocide are interpreted differently in the ICC than elsewhere.