Recent opinions of the Supreme Court,1 as well as statements by several of the Justices in extra-judicial speeches,2 suggest a willingness to look at foreign sources of law as aids in constitutional interpretation. Constitutional scholarship has also taken a comparative turn; numerous scholars now examine non-U.S. constitutional structures and practices to see what insight they may provide for U.S. constitutional interpretation and constitutionalism.
There is nothing terribly new in all of this. Early opinions of the Court and leading treatises of the nineteenth century took international and comparative law far more seriously than courts and scholars in the twentieth century. James Madison studied the constitutions of the world in preparing to write the American document. Early U.S. jurists were schooled on the leading international treatises, the lex mercatoria, the law of prizes, Roman citizenship law, and British constitutionalism. The insularity of this nation's middle years needs more explanation, perhaps, than the turn (back) toward law and legal systems beyond our borders.
This outward-looking approach to U.S. constitutionalism will surely continue, its sources ranging from the mundane (attendance by U.S. judges at foreign conferences) to the useful (growing U.S. interest in human rights jurisprudence in the European Union (EU)). For scholars, the comparative turn represents the most recent attempt to gain a new perspective, to examine assumptions, and to challenge the prevailing wisdom-opportunities provided in days past by various critical legal studies, the various "law and" movements, and historical turns. It is difficult to write these opening paragraphs without mentioning globalization somewhere. So let me add it in terms of legal pedagogy. Quite simply, to be responsive and responsible, law schools need to teach students how to be comfortable in more than one legal system-because so much of modern legal practice crosses borders. Comparative constitutional study has, appropriately, become part of a good liberal arts legal education.
Exactly what influence the comparative turn has had on constitutional doctrine remains to be seen. At present, the nods to foreign sources seem little more than make-weights in opinions that have reached conclusions on other grounds. But theorizing has begun on how external constitutional norms can become authoritative elements in U.S. constitutional adjudication.3 And this is but one piece of a broader internationalist agenda that seeks greater influence for transnational norms. The normative case stresses both national interests and moral advancement.
Once transnational norms become more than points of comparison-once the claim is made that law made elsewhere has weight, force, or bindingness in the U.S. legal system-significant issues of constitutionalism come into play. These issues are frequently stated in doctrinal terms: Does delegation to international organizations violate structural constitutional norms? Does Article III require that international adjudications with domestic effect be subject to judicial review by U.S. courts?4 As international regulation grows apace, these will become real constitutional issues for U.S. courts.5
The likely result is far from clear. U.S. participation in the rising tide of transnational lawmaking shows that significant national interests are at stake. Congress and the executive branch see value in entering into the kinds of arrangements that will raise new constitutional questions. But, of course, it is precisely this new kind of law that may well give the Justices pause.
It might be thought that in the field of foreign affairs the Court will be loathe to exercise muscle, but I think a parallel can be drawn here to the Court's recent willingness to limit congressional power deemed to intrude on the states. Keith Whittington has noted that the new federalism cases have invalidated relatively minor legislation that was not supported strongly by either political party nor a powerful political constituency. …