Paul Hoffman, attorney for the plaintiffs in Kiobel, made this key point early in the oral arguments before the Supreme Court yesterday:
I think one of the most important principles in this case is that international law, from the time of the Founders to today, uses domestic tribunals, domestic courts and domestic legislation, as the primary engines to enforce international law.
This, it seems to me, is something that those who "get" international law understand. Those who remain skeptical about whether international law is "really law," on the other hand, often appear to miss this point. Even with the International Criminal Court, the International Court of Justice, the International Criminal Tribunal for the Former Yugoslavia, the International Criminal Tribunal for Rwanda, the Special Court for Sierra Leone, the European Court of Human Rights, and assorted other international tribunals in existence, few international law cases are heard in international fora rather than in domestic courts. This is why states ought to--and often do--make international human rights norms part of their own law. It is why dealing with corrupt leaders who launder money abroad requires something like the U.S. Kleptocracy Asset Recovery Initiative or the French "biens mal acquis" investigation. And it is why even the U.S. Supreme Court is, from time to time, asked to deal with matters of international law.