My remarks today concern the use of international and foreign law as a source of authority in constitutional interpretation. First, I will discuss what it means to use foreign or international law as authority in the interpretation of the U.S. Constitution. Second, I will assume the truth of originalism as a theory of constitutional interpretation and show why the use of contemporary foreign or international law is incompatible with that theory. Because that lack of compatibility can be simply stated, I will then suggest that the use of foreign and international law is objectionable under even more pragmatic theories of constitutional interpretation.
First, what does it mean to use international law or foreign law as an authority in helping to construe the Constitution? The Supreme Court uses foreign or international law as authority when it gives weight in American constitutional law to propositions because they are part of international or foreign law. There are thus two conditions that must be met for international or foreign law to be treated as authority. The Court has to give such propositions weight and it has to give them weight as foreign or international law.
It is sometimes said by the apologists for the use of international and foreign law that, of course, such propositions have no authority because the Supreme Court is not treating them as binding. But that is a non sequitur. Even Supreme Court precedent does not bind the Supreme Court in that it may be overruled and yet no one would deny that precedent has authority in constitutional law. The real question is whether propositions of international or foreign law are going to be given any weight (i.e. whether their existence could make a difference to the way the Court comes out). If propositions of international and foreign law are not going to be given any weight, I do not have a strong objection to citing them. I still have a quibble: the practice of citing material that is largely decorative may hurt the transparency of the opinion. Multiplying citations to propositions that do not make a difference to the outcome makes it harder to figure out what are the authorities that are doing the work in reaching the result. Certainly if the Court is not giving foreign or international materials weight, the Court should make clear in it's citation practice that foreign and international legal material is being included for some reason other than its intrinsic authority.
Second, my objections are limited to propositions that are given weight by virtue of their presence in foreign or international law. Depending on their theory of constitutional interpretation, Justices may have other good reasons to use a proposition occurring in foreign or international law as a source of authority in constitutional interpretation. For instance, Justices may consider moral principles relevant to constitutional interpretation and may believe the proposition that happens to be contained in international and foreign law is a morally good one. But in that case the methodological question is what weight morality should have in constitutional construction, not the relevance of foreign or international law.
Let me make an analogy. Justices generally give our own domestic precedent weight, regardless of whether precedent is itself soundly reasoned. Justices could simply look at precedent to determine whether it contains reasoning that they judge to be good by some metric provided by the correct theory of constitutional interpretation. That would just be using precedent for informational value. (1) But Justices generally do use a precedent as authority as well, i.e. for its disposition value. Whatever its informational value, a precedent will make subsequent court opinions more likely to come out in its direction simply because it is precedent. My subsequent critique depends on international and foreign law being given weight beyond its informational value. …