The United States Supreme Court and Foreign Law

With this post, we quickly set aside the issue of interdisciplinarity in comparative law and focus on applied comparative law in a broader sense. Specifically, I would like to look at the question whether the United States Supreme Court (and courts in general) should consider foreign law and practices.

In this regard, Justice Breyer of the United States Supreme Court just published his book The Court and the World: American Law and the New Global Realities. The book essentially is a commented synopsis of recent Supreme Court decisions that mention foreign law. Most of these decisions concerned the interpretation of international treaties or statutes where consideration of foreign law is fairly accepted. Sometimes, however, foreign law was consulted on questions relating to the United States constitution and its interpretation. In particular, issues relating to national security and antitrust triggered a look across borders, but also questions about gay rights and the death penalty.

According to Justice Breyer, foreign law – while by no means binding – could be quite “instructive” in cases involving questions of constitutional interpretation in general and more specifically questions relating to the Eighth Amendment and the death penalty.

“It [the Eighth Amendment] uses the word ‘unusual,’ and the founders didn’t say unusual in what context.”

Generally, judges – and lawyers – across borders could learn from each other. Unfortunately, drawing inspiration from abroad is still very limited – not just for ideological reasons, but also because of lack of understanding foreign law and its terminology.


  • Adam Liptak, Justice Breyer Sees Value in a Global View of Law, The New York Times, September 12, 2015 (available here)

Interdisciplinarity – Lessons from Applied Comparative Law

In my previous post, I pointed out that comparative law could benefit from other disciplines. Such incorporation of external research needs to be done in a way that makes it acceptable from a legal standpoint. And principles of (applied) comparative law may just be the key – admittedly a somewhat circular reasoning, but nevertheless something worth looking into.

Applied comparative law considers the question of legal transplants, i.e. which legal provisions could be transferred from country A to country B. In order to determine which law should be transferred, lawyers have to figure out the overall best solution by taking into account what is reasonable and just. Here, the issue of cultural and ideological discrepancies arises: because what works well in country A does not necessarily be acceptable in country B. So in the end, lawyers have to decide on a case-by-case basis whether the prima facie better law is in fact ideal in the country it should be adopted.

So what does this previous paragraph tell us about interdisciplinary comparative law? Adopting an idea or reasoning from another discipline might just be similar to transferring legal provisions from country A to country B. Thus, any effort in incorporating interdisciplinary research has to determine on a case-by-case basis whether a particular idea from another discipline is reasonable and just in the particular comparative law research at hand. In this regard, Giesen proposes a (non-exhaustive) set of questions that any lawyer who considers empirical research should ask himself before incorporating this research into his work: 

– whether the empirical work is in fact relevant for the question of law that arises,
– whether the work is up to the current state of the art in the field methodologically, as well as regards its research design, etc., and its implications,
– whether (more generally) the research is valid and reliable,
– whether there is conflicting empirical work on the same issue,
– whether the study has been replicated and confirmed or not,
– whether the study is but one building block of a larger set of studies needed for policy implications,
– whether the researcher is both an expert and objective and independent, and so on.

The advantage of this approach is that it may help prevent premature adoption of empirical ideas into comparative law research. 


  • Ivo Giesen, The Use and Incorporation of Extralegal Insights in Legal Reasoning, 11 Utrecht L R 1-18 (2015).
  • Konrad Zweigert & Hein Kötz, An Introduction to Comparative Law 33-47 (1998).

Interdisciplinarity in Comparative Law – A Blessing or A Curse?

Interdisciplinary research – the collaboration or conglomeration of knowledge of two or more disciplines – is probably one of the main features in academia over the last 50 years. In comparative law, interdisciplinarity has been honed as the sine qua non. Yet, some have warned against or even criticized interdisciplinary efforts in comparative law research.

Comparative law is often linked with social sciences, economics and linguistics. Some of this interdisciplinary research has been more accepted than the other. Acceptance is usually contingent upon the perceived compatibility of the fields. Thus, comparative law research drawing from legal history is much more recognized than the application of law and economics concepts on a macro-comparative question.

Such bias is unfortunate, because comparative law as a discipline may greatly benefit from thinking outside the box by looking at other – more unusual -fields of research. The challenge is just to make sure that the basic principles of all disciplines combined are kept intact. Generally, collaboration among researchers seems to be the ideal way to go. Yet, unfortunately, legal academia tends not to be very open for that. So another solution might be to ensure better knowledge on an individual level through in-depth study of the other field used.

In subsequent posts, I intend to discuss some recent research on and in interdisciplinary comparative law.


  • Jaakko Husa, Interdisciplinary Comparative Law – Between Scylla and Charybdis?, 9 J. Comp. L 28-42 (2014).
  • Pierre Legrand, Le Droit Compare 3e ed. 47-48 (2009).
  • Geoffrey Samuel,  Does One Need an Understanding of Methodology in Law Before One Can Understand Comparative Law Methodology? 177-208, in: Methodologies for Legal Research: Which Kind of Method for What Kind or Discipline (Mark van Hoecke, ed. 2011).