Panel 5.1 / Delineating the interpretative stage in the ‘Life-Cycle’ of customary international law

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5.1.1 / Riccardo di Marco
Customary International Law: a Foreword to Identification v. Interpretation

Traditionally, academic authors working on the interpretation of public international law, state that only treaties can be interpreted. Therefore, this process is completely distinguishable from the one of identification. Indeed, treaties are generally easy to identify, and once this identification has been completed, it is in most cases, possible to interpret these treaties with the same ease. On the contrary, if one focuses on general international law, it is often argued that the process of its interpretation is inherent to its identification. Thus, the moment in which one establishes the existence of customary international law, one is also obliged to proceed to the identification of this type of rule. Hence, many scholars do not think that it is possible to distinguish the establishment of the existence of a customary rule from the determination of its contents. In this respect, it is of high significance that the recent work of the International Law Commission concentrates on the identification of customary international law. This highlights the fact that customary rules and treaties are of different nature indeed. In fact, according to the International Law Commission, customary international law, an unwritten source of law, can only be identified and thus not be interpreted. Based on this statement, one could argue that the use of the word “identification” is of higher appropriateness than to the word “interpretation”. Nevertheless, it should not be forgotten that the primary intention of the interpretation of every rule, in every legal system, is indeed to determine whether – once both its content and its general and abstract scope are established – it can be applied to the circumstances of the particular case. It therefore seems difficult to argue that the process of the identification of a rule is indistinguishable from the one of its interpretation, even in case of an unwritten rule. This point of view indends to assure the maintenance of a reasonable flexibility in the application of custom. Claiming that customary international law cannot be interpreted would indeed artificially restrict the interpreter’s freedom of manoeuvre. Furthermore, it seems difficult to argue that a customary rule – previously established – should be applied to new circumstances falling within its scope, regardless of general principles of interpretation used for the application of treaties. The aim of this paper is to discuss whether it is possible to use the word “interpretation” in regard to customary international law. In a second time, it focuses on the question whether it is possible to acknowledge that the process of interpretation of customary international law is separate from the one of its identification.

5.1.2 / Mariana Clara de Andrade
Identification of and Resort to Customary International Law by the WTO Appellate Body

The recourse to customary international law by international adjudicators is a valuable element contributing to a better understanding of this source of international law. The aim of this article is to examine the recourse to this source by the WTO’s Appellate Body. This international adjudicative forum is particularly interesting due to its limited material jurisdiction, as it can only assess WTO law. This paper thus analyses the means through which the adjudicators identify customary international law and what are the customary norms they resort to. Moreover, given the mentioned jurisdictional limitations of WTO adjudication, it is relevant to examine whether this recourse is limited to serve as interpretative aid to WTO provisions or whether it amounts to the application of these ‘extraneous’ sources. It is therefore relevant to understand the difference between the use of customary rules for purposes of interpretation and the actual application of these sources within WTO dispute settlement. It is concluded that the Appellate Body’s reliance on customary international law is limited: it only resorts to codified rules of treaty interpretation and state responsibility. Moreover, it does not proceed in properly identifying rules of international law, but merely asserts their existence and relevance on the basis of other authoritative references. Through this methodology, and by using customary rules under only these two ‘fields’, the AB has more leeway in not overstepping the line of its jurisdictional limitations.

5.1.3 / Kostiantyn Gorobets
Practical Reasoning and Interpretation of Customary International Law

Customary international law as a phenomenon provides a solid ground for testing theories and conceptions of legal normativity and authority. It challenges the simplest yet very common idea that law should be identified by its ‘author’ and interpreted according to his or her will or intention. Customary (international) law does not fit to this scheme as it usually has no ‘author’ in the same way as, for example, treaties, and its authority depends more on the content rather than on the origin of its rules. Consequently, this makes the originalistic interpretation of customary international law irrelevant, if not impossible.

An alternative approach to explaining the authority of customary international law and to developing a feasible strategy for its interpretation is theory of practical reasoning. Here, rules are considered as second-order reasons for action that represent a certain balance of first-order reasons. Rules are time- and labour-saving devices which allow subjects to take ‘shortcuts’ in their practical reasoning, avoiding in such a way deliberations regarding the best balance of the first-order reasons every time this is relevant. Thus, the authority of rules depends on how effectively they perform their ‘shortcutting’ function pre-empting their addressees from recurring to their underlying first-order reasons.

The interpretation of customary international law, from this perspective, is a twofold enterprise. On the one hand, the interpretation is aimed at discovering what first-order reasons guide the actions of states and what their relative strength is. The first-order reasons here represent all the facts that count for or against performance of certain actions of states at the stage of rule formation. The crystallisation of a customary rule is therefore a formation of a shortcut in practical reasoning, when a customary rule replaces deliberations about the relevant first-order reasons and, to some extent, excludes them from consideration; a customary rule becomes a reason for action in its own right representing a balance of the first-order reasons.

On the other hand, interpretation is aimed at the evidence of states’ perception of the normative strength of this already existing customary rule, and at whether they consider this second-order reason as creating a legal obligation to act or refrain from acting for this reason. Opinio juris, therefore, relates to a second-order reason, i.e., to an already existing customary rule. This indicates that interpretation of state practice and its underlying first-order reasons is distinct from the interpretation of opinio juris that focuses on second-order reasons. Interpretation of the first-order reasons relates to the content of a rule, whereas interpretation of the second-order reasons—relates to its normative strength.

The practical reasoning-based interpretation of customary international law allows one to avoid complications/limitations of the authorship/origin-focused approaches. It also provides a better understanding of relations between state practice and opinio juris.

5.1.4 / Marina Fortuna
Interpretation of Customary International Law: You Know It When You See It?

This contribution grapples with the question of how to recognize the stage of ‘interpretation’ in ‘the life-cycle of customary international law’. First, it briefly outlines the ‘stages of development’ of customary international law. It divides the life of customary international law into three stages: the formation stage, the existence/identification stage and the concretization/interpretation stage, each of which differs with respect to the function they perform in the development of a full-fledged customary rule.

Secondly, this paper briefly addresses the two critiques of non-interpretability of customary international law and defines ‘interpretation’. Here, reference is made to the distinction made by Francis Lieber between construction and interpretation, but also to the difference between interpretation of state practice and interpretation of a customary rule.

Finally, what makes the core of this paper is an analysis of the problems that exist in recognizing the stage of interpretation in the case law of international courts and tribunals.

The first issue is that, oftentimes, judges are unaware that they engage in the interpretation of customary rules, which is why they do not explicitly acknowledge this normative process. But this silence should not be construed against interpretation of CIL. Borrowing from the language of the rules of treaty interpretation, the instances of customary law content determination become easy to detect. By ‘rules of treaty interpretation’ I refer not only to rules embodied within Article 31 VCLT, but also those outside the VCLT.

A second problem is that judges ‘blend’ interpretation of custom with treaty interpretation. There are cases where these two normative processes may occur simultaneously. Nonetheless, this should not be understood as a blanket authorization to resort to interpretation of treaties in order to determine the content of customary rules.

Lastly, this contribution tackles the problem of judicial choice – sometimes the employment of identification over interpretation or vice versa is just a matter of judicial preference. This problem stems from the design of customary international law, but may be overcome with a wider recognition of CIL interpretation.