Elena Kagan, under questioning from Sen. Chuck Grassley, said there were certain cases in which it would be “appropriate” for the Court to cite international law. As an example, she gave the Hamdi v. Rumsfeld case in which the Court ruled that U.S. citizens being detained indefinitely as enemy combatants must be granted the option of challenging their detention in court.

Here were her full comments, after Grassley asked, “If confirmed, would you rely on or cite international foreign law when you decide cases?”:

I think it depends. There are some cases in which the citation of foreign law, or international law, might be appropriate. We spoke earlier, I forgot with which of the Senators, about the Hamdi opinion. The Hamdi opinion is one in which the question was how to interpret the authorization for the use of military force. And Justice O’Connor in that case, one of the ways in which she interpreted that statute, was by asking about the law of war and what the law of war usually provides. What authority the law of war provides. And that’s a circumstance in which in order to interpret a statute giving the President various wartime powers, the Court looked at what the law of war generally provided. So there are a number of circumstances. I think, I mean, another example would be suppose the President has the power to recognize ambassadors under Article II. And there might be a question, well, who counts as an ambassador? And one way to understand that question is to look at what international law says about who counts as an ambassador. And that may not be determinative. But it would be possibly something to think about and something to cite.