Tony Arend discusses the recent decision in Kiobel:
"The methodology the court uses for determining the existence of a rule of customary international law is consistent with what I believe to be the correct, positivist understanding of international law. (An approach that I have elaborated upon in more detail here.) In order for a rule of custom to exist there must be both state practice and a belief by states that the practice is obligatory, opinio juris. What the court avoids is assuming the existence of a rule of custom because it might seem logical for such rule to exist. In other words, the court will admit that a rule of custom exists if, and only if, it can demonstrate that state practice created such a rule. I think this is the correct method for evaluating the existence of a rule of custom.
[On the merits,] I find the arguments advanced by Judge Carbranes quite persuasive. That is, the court does seem to demonstrate that states have not created a specific rule of custom establishing corporate liability."
Anthony Clark Arend is Professor of Government and Foreign Service at Georgetown University. On July 1, 2008, he became the Director of the Master of Science in Foreign Service in the Walsh School of Foreign Service.