- Customary international law — Ordre public — Vienna Convention on the Law of Treaties — Extraterritorial application of treaties — UN Charter — Peremptory norms / ius cogens
When the Vienna Convention on the Law of Treaties confirmed the existence of peremptory norms of international law (jus cogens) they were conceived, like Roman jus publicum, as absolute law that could not be altered by the will of individual States. Scholars then transformed the concept into the manifestation of public policy (ordre public). They also argued for widening the scope of its application to unilateral legal acts and customary international law. A recent trend in academic theory assigns jus cogens an essential role in the constitutionalization of international law, postulating it either as hierarchically higher order or as embodying the constitutional principles. In view of the rashness of scholars in proclaiming the peremptory character of norms and also of the inexpertness of the European and national courts in applying supposedly peremptory international norms in their decisions, it seems better to keep jus cogens at its original task.