Panel 4.2 / Domestic Courts’ Lessons on the Theory and Interpretation of CIL
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From Customary Law Ascertainment to Interpretation: the Role of Domestic Courts
The TRICI project observes that ‘in the study of customary international law (CIL) there
is a critical gap in understanding how customary international law (CIL) can be applied in
individual cases once it has been formed’. The project then sets for itself the goal to
uncover rules of interpretation of customary international law. In the words of the
project, if such rules were to exist, CIL need not be induced each and every time, by
reference to state practice and opinio juris, or asserted by judges.
Such a goal appears to be at loggerheads with the very nature of CIL as a flexible and
protean source of international law, that is at least potentially in a state of constant flux.
Given these characteristics, judges always have to revisit the very existence of customary
norms de novo. Although unlikely, it is after all not impossible that customary norms form
almost overnight (instant custom). Methodologically speaking, judges have to concern
themselves first and foremost with the ascertainment and identification of norms of
customary international law, before they can apply and interpret such norms. This follows
from the very text of Article 38(1)(b) of the ICJ Statute, which provides that the ICJ (and
courts more generally one may well posit) ‘shall apply’ … ‘international custom, as
evidence of a general practice accepted as law’. Pursuant to this provision, courts can
only apply a customary norm after they have first established its evidence-based
existence. This process is admittedly interpretative, but it is so only in an evidentiary
rather than normative sense. Instead of interpreting previously crystallized norms by
analogy with Article 31-32 VCLT, judges interpret evidentiary materials placed before
them, with the aim of distilling, or not, customary norms from those materials.
A look at the practice of courts reveals that they do not usually engage in thorough
processes of customary international law-identification, however. This applies in
particular to domestic courts, which either have little customary international law
expertise, or which deal with cases in which the customary international law question
does not occupy a central place in the dispute. This paper demonstrates empirically that
domestic courts often apply rather than ascertain customary international law. They tend
to rely on, and defer to other authorities (e.g., the ICJ, the ILC), even if occasionally they
embark on a serious law-ascertainment process of their own. While such ‘other
authorities’ only have evidentiary value that should be weighted with other materials
evidencing (or not) the existence of a particular customary norm, one cannot escape the
impression that domestic courts are simply giving effect to, or applying pre-existing
customary norms. If that is true, there is in principle room for the development of rules
of interpretation. The fact remains, however, that domestic courts continue to hew to
the fiction that they are law-finders rather than law-appliers; accordingly, none of them
has relied on or developed such rules. It is only if they own up to their limited agency in
identifying customary law, that rules of interpretation can appear on the horizon.
Once You Reach the Top of a Positivized Legal System, Customary Law Emerges Again. Hints from the Italian Constitutional Court
In general, the Italian constitutional legal system denies any status to customary law
within Italian law. The only customary rules mentioned in the constitutional system are
those of international law, which are incorporated into the Constitution through Article
10(1): “The Italian legal system shall conform to the generally recognized principles of
international law”. This structure comes from the traditional, positivistic preference for
written and codified rules, adjusted to meet the need to curb the Nation State from the
possible excesses which historically led to fascism and WWII, by enlarging the sources
of law above and beyond the Constitution.
The Italian Constitutional Court has often being asked to adjudicate on Art. 10(1) in
generic terms, or by reference to specific treaties – including the ECHR and the UDHR.
On almost every such occasion, the Court has refused to consider treaties as included
under Article 10, and, therefore, it has never ruled on the difficult relationship between
written law and customary rules crystalized, codified in an international treaty. Only in
one case did it deal with written international law and customary rules together. In that
case, the Court made generic references to several international treaties expressing, in
the Court’s view, a certain “principle of international law”, without investigating its actual
customary nature. More recently the Court referred to jus cogens and state immunities,
but, again, without engaging in an analysis of state practice.
In addition to these cases dedicated to customary international law, the Court has heard
a few cases in which it has had to adjudicate on the existence of constitutional customary
rules among domestic State organs. It refrained, however, from reflecting on, or drawing,
a precise theory concerning them and their place in the theory of sources.
While customary law rules have an important position in international law and law in
general, the Italian Constitutional Court still appears to have some difficulty accepting its
role and handling it. This presentation will be both the occasion to present the Italian
case law on customary international law, and to reflect on the importance of customary
international law even in a legal system that relies only on written law.
Customary International Law as a Tool for Federal Dispute Settlement: The Surprising Relevance of Customary International Law for the Domestic Legal Order in Germany and Austria
The publication of Triepel’s Völkerrecht und Landesrecht (1899) was a milestone in the development of international legal theory. It was also a very important contribution to the intellectual debate in Germany and the German-speaking world on the relationship between international and national law. In both the German Reich and in Austria Triepel’s work played an important role in the development of the dualist and transformist approach still dominant today. As a result of this, both the German Constitution of 1919 (the Reichsverfassung) and the Austrian Constitution of 1920 (the BundesVerfassungsgesetz) contain a paragraph dealing with the internal position of customary international law (art. 4 RV and art. 9 B-VG respectively). The Staatsgerichtshof für das Deutsche Reich (RStGH), the specialised court introduced by the 1919 Constitution to deal with federal disputes decided a number of interesting cases concerning disputes between two or more States in Germany by using a number of customary international norms incorporated through article 4 of the Constitution. In my presentation, I will analyse these decisions to see how and why the RStGH used these norms to settle conflicts of a domestic nature and how they were interpreted to be useful in a purely domestic context. The post-war German Constitution, the Grundgesetz, has an almost identical article to article 4 of the 1919 Constitution, article 25 GG. The main difference is that article 25 strengthens the domestic position of customary international norms by granting them prevalence over federal acts. Surprisingly however, the Bundesverfassungsgericht (BVerfG) refuses to acknowledge the relevance of customary international law for the settlement of federal disputes. Instead, it opts for the formulation of unwritten principles seen as of domestic origin that are materially identical to the norms used antebellum by the RStGH. My analysis will focus on the question what, if anything, has changed by this different approach. The analysis on Germany will be complimented by a short excurse to Austria to see if and how the Verfassungsgerichtshof (VfGH) uses article 9 B-VG to settle disputes between two or more Austrian states and if this approach differs from the German one. Thus, my presentation will shed light on the question whether and how customary international law can be a useful tool for purely domestic legal disputes.
Old, New, Borrowed, or Blue: How can we Learn from the Interpretive Practices of Domestic Courts?
The interaction between domestic and international law is a dynamic relationship which
has received renewed scholarly interest in the past decade. In the traditional
conceptualization of domestic v. international law, the two levels interact in broadly two
ways: i) the ‘monist v. dualist’ framework for the purpose of conceptualizing international
law’s domestic application, and ii) the ‘sources of international law’ framework for the
purpose of conceptualizing domestic law’s role in the international legal sphere. In the
latter in particular, domestic law and legal practices may feature internationally through
the mediums of customary international law (CIL) or general principles.
More interestingly however, scholars and practitioners are increasingly recognizing that
the domestic and international levels interact in a much wider and more diverse manner
than the one provided for in the traditional frameworks. Studies of the International Law
Association (ILA) have shown that domestic courts engage with international law in
significantly more diverse manners beyond the ‘monist v. dualist’ framework and the
traditional framework of sources. On the other hand, domestic legal principles and
approaches have also found their way into multiple fora of both international adjudication
and international law making. Thus, it has been observed that the interaction between
the two levels also implies mutual influence.
This paper will examine the relationship between domestic and international law with a
particular focus on CIL and the rules for its interpretation. More specifically, the objective
is to explore how domestic interpretive practices have influenced interpretation on the
international level, and how they may inform or otherwise influence the development of
rules for the interpretation of CIL. Bearing this objective in mind, the paper will examine
the interaction between domestic and international law, with a view to developing a
theoretical framework which captures the ways in which international law receives or
learns from domestic legal practices in the field of CIL. In particular, the paper will focus
on answering the question “how can international law learn from the interpretive
practices of domestic courts?”. Thus, the paper will develop a working theoretical
framework of interaction aimed at capturing the ways in which international law may
learn from domestic law and practices with respect to CIL interpretation. This framework
will serve as the basis for further research on the topic.
The paper will examine theoretical frameworks of interaction developed by several
authors in the fields of general international law, international economic law, and
environmental law. Then, building on these findings, the paper will turn to developing a
working theoretical framework tailored to the interaction between domestic and
international law specifically with respect to interpretive practices. The result will be a
working theoretical framework which maps the ways in which international law can learn
from the interpretive practices of domestic courts, for the purpose of developing rules
for CIL interpretation on the international level.
TRICI-Law - The Rules of Interpretation of Customary International Law 