Penn State International Law Review

First Paragraph

Since its first "official" recognition as a concept of international law in the 1969 Vienna Convention on the Law of Treaties (the "Vienna Convention"), jus cogens has had both a strikingly unremarkable and a highly controversial existence. On the one hand, its impact on the actual practice of international law and, more specifically, the rulings of international and domestic tribunals, has been particularly limited. On the other hand, however, jus cogens has triggered a lively debate whose controversial character resembles, in several respects, the lex mercatoria discussion in international commercial law.