Despite recent polemics, the use of international law in constitutional interpretation, as one factor among others, is highly traditional and eminently proper. Some international law is too important to the place of the United States in the world for our constitutional jurisprudence to ignore; some international law provides useful functional or normative insights on which constitutional adjudication can draw.
As a matter of division of labor, (1) I will concentrate here on the use of international--as opposed to foreign--law in constitutional interpretation. Some criticisms of recent Supreme Court decisions have coupled attacks on these two categories of law, and some criticisms suggest a lack of awareness that there is any difference between them. In fact, there are important differences between the two categories, and the arguments for their relevance do not entirely coincide. At the same time, the two categories partly overlap.
Judge Frank Easterbrook and Professor Steven Calabresi, in their contributions to this symposium, appear to treat these categories as interchangeable for purposes of their arguments about "foreign law," and within the limits of their respective methodologies that may be appropriate. (2) From the broader (and I believe more justifiable) perspective taken in this Article, the differences can be significant.
The category of "international law" covers a wide variety of different kinds of norms, such as customary international law, multilateral treaties, and bilateral treaties. It includes treaties to which the United States is a party, treaties that we have chosen not to ratify, and treaties that we are not eligible to ratify. Some international law is part of the basic legal architecture of the world we live in. Some international law is particularistic and ephemeral.
These distinctions are relevant to how various norms of international law should be used in constitutional interpretation, but their existence should not disqualify the entire category from consideration. International law as such is not ephemeral and cannot be dismissed as a pack of "foreign moods, fads or fashions." (3)
The category of "foreign law" could be understood principally as referring to the domestic legal systems of foreign states, including their national constitutions, statutes, and other domestic norms. (4) Sometimes discussions focus even more narrowly on foreign constitutional law, but the content of national constitutions varies greatly, and some systems give statutory answers to questions that other systems treat as constitutional. "Foreign law" can also be understood more broadly as further including the international obligations of a foreign state, and especially those that do not bind the United States, such as regional treaties on other continents, bilateral treaties among foreign states, and global multilateral treaties that the United States has not ratified. Thus, some "foreign law" may also be "international law."
In recent cases that have excited controversy, such as Atkins v. Virginia, (5) Lawrence v. Texas, (6) and Roper v. Simmons, (7) the Supreme Court has primarily cited to foreign domestic law and to international law binding on other countries. The international sources included regional human rights treaties and jurisprudence thereunder, and the United Nations Convention on the Rights of the Child, which the United States has not ratified. The Court in Roper also noted the prohibition on the juvenile death penalty in the International Covenant on Civil and Political Rights, which the United States did ratify in 1992, but with a unique reservation excluding that particular provision. (8)
Treaties ratified by the United States without pertinent reservation, on the other hand, are not foreign law at all. The Supremacy Clause of the U.S. Constitution declares them to be supreme law of the land. (9) Treaties may be viewed as having a foreign aspect, in that the United States cannot adopt them unilaterally, and cannot modify them without the consent of treaty partners. …