References to foreign law in Supreme Court opinions have become controversial.... True, the references have increased somewhat, but they remain rare, and no one suggests that the court has directly based any of its interpretations of the Constitution on foreign authority. As the issue was framed recently in a debate between Justices Stephen Breyer and Antonin Scalia, it comes down to this: The former says that if a judge abroad has dealt with a similar problem, "Why don't I read what he says if it's similar enough? Maybe I'll learn something." Yet the latter would exclude such material as wholly...