Foreign Law and the Modern Ius Gentium

I. INTRODUCTION Is it ever appropriate for American courts to cite or defer to foreign law? The question arose last Term in a bitter dispute among the Justices of the U.S. Supreme Court in Roper v. Simmons, (1) the juvenile death penalty case. (2) One of the frustrating things about Roper, however, is that no one on the Court bothered to articulate a general theory of the citation and authority of foreign law. (3) Writing for the Court, Justice Kennedy said that it was "proper" to take foreign law into account and that referring to the laws of other countries could be "instructive" for the Court's interpretation of the Eighth Amendment. (4) But he did not explain the jurisprudence behind this view. (5) Nor did the Roper dissenters articulate a theory of citation to foreign law that they could squarely refute; they simply denounced the practice. The theory that is called for is not necessarily a complete jurisprudence. But it has to be complicated enough to answer a host of questions raised by the practice: about the authority accorded foreign law (persuasive versus conclusive), about the areas in which foreign law should and should not be cited (private law, for example, compared to constitutional law), and about which foreign legal systems should be cited (only democracies, for example, or tyrannies as well). The theory has to be broad enough to explain the use of foreign law in all appropriate cases: too many scholars call for a theory that will explain the citation of foreign law only in constitutional cases. (6) The theory has to be persuasive enough to dispel the serious misgivings that many Americans have about this practice: why should American courts cite anything other than American law? Above all, it has to be a theory of law. The argument cannot just be that good diplomacy requires us to ingratiate ourselves with the Europeans. (7) It must explain why American courts are legally permitted (or obliged) to cite to non-American sources and how that practice connects with the status of courts as legal institutions. An example may help get at the sort of theory I have in mind. When courts cite their own precedents, they do so on the basis of the theory of stare decisis, which provides a platform on which judges can articulate and defend their deference to precedent. It explains why deference is appropriate even for cases in which justice or policy seems to require a different result. It explains why precedent is more important in some cases than in others. And it explains its relation to various sources of law (the difference between stare decisis in common law and in constitutional interpretation, for instance). No doubt the details of stare decisis are controversial. (8) But even if one disagrees with a judge's conception, it is surely better that he should articulate such a theory than that he simply give the impression that he thinks deferring to precedent is a good idea. We should require nothing less for the citation of foreign law. In his dissent in Roper, Justice Scalia said that the Court's citation of foreign law was unprincipled and opportunistic. (9) Even this observation, however, does not mean that there cannot be a good theory to support the practice. Using my analogy again, Justice Scalia has sometimes argued that the Court's following and departing from precedent in cases involving individual rights is unprincipled and opportunistic. (10) But it does not follow that he rejects stare decisis or that he thinks it is not worth developing a theory of precedent. Similarly, we should not reject the idea of a theory of the citation of foreign law simply because we see foreign law being cited opportunistically; we should reject it only if we think inconsistent and unprincipled citation is inevitable under the auspices of such a theory. Though it appears from his dissent in Roper that Justice Scalia's denunciation of the citation of foreign law proceeds without any appreciation that such citation should be based on a theory, dicta from his recent concurrence in Sosa v. …