The International Court of Justice and “non-universal” customary norms

The wording of Article 38(1) of the Statute of the International Court of Justice might imply that no other customs apart from the “universal” ones could be considered as sources of international law. However, the International Court of Justice took a proactive role and recognised the existence of “special” (i.e. local or regional) customary rules and perhaps employed a more creative approach and actually “read them” into Article 38(1) of the Statute. Moreover, the Court also seems to have created the “rules on how to ascertain the rules” of special custom, when it set a higher threshold for proving its establishment through its case-law in Anglo-Norwegian Fisheries, Asylum, Nationals in Morocco and Right of Passage cases. The 2009 Navigational and Related Rights case seems out of sync with the previous cases on special custom, and it remains to be seen whether it can be considered as more than anomaly in the Court’s jurisprudence. Even though the International Court of Justice seemingly had quite a proactive role with regards to special custom, it appears that it avoided to pronounce explicitly on some issues such as how to ascertain opinio juris or relation between general and special customary rules