Customary International Law as a Dance Floor: Part I

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International lawyers’ thirst for argumentative freedom seems unquenchable. Nowhere is this more conspicuous than in the debate unfolding around the current work of the International Law Commission (hereafter ILC) on the identification of customary international law. Indeed, whilst the ILC has espoused a rather self-restrained approach so far, its study on the identification of customary international law has laid bare the prodigious emancipatory fervour at work outside the Palais des Nations. Particularly remarkable is the widespread presupposition that, in order to allow customary international law to serve the various agendas of ambitious 21st century international lawyers, one can simply toss out some of the elementary constraints around which the 20th century modern theory of customary international law had been shaped.

As this short note will argue, the emancipation from the traditional theory of customary international law at play in international legal scholarship, and unveiled by the current work of the ILC, is perplexing. This is certainly not because the traditional and modern theory of customary law should be redeemed. The inconsistency and deceitfulness of customary international law have long been proven. It is even astounding that such a frail gospel has been able to survive for so long. What is perplexing is that international lawyers may currently be replacing the duplicitous prison of customary international law with a dance floor where (almost) anything goes while still believing that this uncomplicated discourse-production technique can serve all their – sometimes extravagant – ambitions. It is contended in the following observations that this argumentative freedom is not only bound to be short-lived but may also end up depriving international lawyers of what has so far been a surprisingly useful discursive technique to create authority and make demands of the world.

Prolegomenon: customary international law and the ever-lasting eviction of rigorous minds

Before shedding light on the emancipatory frenzy uncovered by the work of the ILC on the identification of customary international law, it should preliminarily be acknowledged that the intellectual prison of customary international law has never been hermetically sealed. The walls of the prison of custom have always been rather porous and permeable and the sentinels rather lenient. Such porosity is not to be lamented because it is part of the raison d’être of this doctrine, rather than its fatal flaw. Customary international law has always been valued for its flexibility by both judges and legal advisers, the former because they could easily promote its development, the latter because they could contest it. In this respect, it must be recalled that when it was introduced in the Statute of the Permanent Court of International Justice, such malleability was meant to delegate a great deal of public authority and norm-making power to the newly constituted judicial body. Sceptics who then thought that custom was not a theory about the sources of international law but rather a device to delegate law-making powers to the judge, had a – very compelling – point.

Unsurprisingly, judges and legal advisers have not been the only one to relish the leakiness of the theory of custom. Activists and legal scholars have continuously found in the theory of customary international law a convenient instrument to vindicate the progressive development of international law and its expansion in areas which they perceive as being insufficiently regulated by it. In that sense, customary international law has much more in common with the idea of softness of law than with the other traditional sources of international law. Like soft law, customary international law is meant to provide all actors engaged in the business of the application of international law with a much appreciated “comfort zone” with a view to either expanding or restricting international law. The price for that, however, is that discourses, literature and interpretive practices on customary international law can, at times, prove extremely frustrating for a legal mind in search of conceptual rigour. Yet, this predicament has generally been deemed endurable.

Wisdom at the Palais des Nations

The ongoing emancipation from the constraints of modern customary law contrasts with the welcome pragmatism vindicated by the Special Rapporteur of the ILC whose effort and choices must be commended. Indeed, Sir Michael Wood has so far convincingly sought to keep the work of the ILC in a reasonable (but not less challenging) low-altitude orbit. There are three particular choices made by the Special Rapporteur which must be acclaimed. It is hoped that that such choices will be upheld in the course of the work of the ILC in the coming years. It suffices to mention them briefly to show the extent to which at they are at variance with the free-for-all going on outside the Palais des Nations.

First, the Special Rapporteur’s suggestion to leave questions of ius cogens aside should be strongly supported. Despite the resilient enthusiasm for an ubiquitous concept of ius cogens, the Special Rapporteurs is right in not conflating the making or primary norms with the making of hierarchies – even if the latter manifest themselves as limitation to freedom of contracts. The ILC should not yield to the common inclination of those scholars that see the world through ius cogens to construe questions of hierarchies as questions of sources.

Second, the Special Rapporteur has resisted the calls of some members of the ILC to engage with the question of the nature of the custom-ascertainment criteria, that is the nature of the rule of recognition found in the theory of customary international law. Even if his methodological choices will inevitably denote a jurisprudential position on the matter, this theoretical self-restrain is certainly prudent. Calls for a venture into this question bespeak an underestimation of the contentious character of this jurisprudential debate. There is no agreement in jurisprudence and legal theory as to whether the criteria of law-identification in a legal system constitute rules properly so-called or, more simply, sets of beliefs or sets of practices. Moreover, irrespective of whether judges may subjectively feel bound by a possible rule in this respect – which is a question of source of authority and not of source of law, the ILC does not seem to be the adequate body for an adventure into this explosive jurisprudential matter.

Third, the Special Rapporteur has been reluctant to open the debate between new and old custom. This choice is perspicacious. The ‘new custom vs old custom’ controversy has always been a false debate. In mainstream legal scholarship, the former is meant to be more inductive whilst the latter is understood as being more deductive. Yet, the dichotomy remains very inconclusive, for even the traditional approach is largely deductive (see here). Albeit being allegedly inductive, traditional custom puts in place a pre-formed hypothesis that leads to the production of a limited number of empirical outcomes. Likewise, the sampling of evidence rests on a predefined pattern and a predefined sequence. The practice is also tested in a way that is informed by the question raised: is there a customary rule on this matter, has the rule on this matter disappeared, does the rule on the matter now include this phenomenon or actor? In that sense, there is almost nothing new in the so-called ‘new custom’. The difference between the old and new custom is just a matter of degree in the deductive process. For that reason, the Special Rapporteur is well-advised to invite the ILC to stay away from this dichotomous view on customary international law.

Revelling on a new dance floor

Unfortunately this prudence is in short supply amongst the community of international legal scholars. On the contrary, the self-restraint of the Special Rapporteur seems inversely proportional to the agitation witnessed outside the Palais des Nations. It is not only that everyone now feels an urge to speak about the identification of customary law. It is rather that it now seems possible to say anything about customary international law without running any risk of epistemic invalidation. The traditional constraints on the making of arguments based on customary international law have been growing thinner. All-in-all, the intellectual prison of custom seems to be gradually transformed into a large dance floor where (almost) every step and movement is allowed or, at least, tolerated.

It is the aim of the observations formulated in the second part of this blog post to spell out a few of the steps and movements currently seen on this new dance floor where any argument on customary law is allowed to fly. Before concluding this first part, an important preliminary caveat must be formulated. Revelling under the emancipatory sound of a liberating theory of customary international law should certainly not be bemoaned. Transforming a prison into a dance floor is a cool thing. Such a conversion looks even more justifiable now that we are all well aware of the fundamental contradictions of the theory of customary international law and the false constraints it places on international legal argumentation.

Yet, in shedding light on the manifestations of this new feeling of liberty witnessed within debates about customary international law, the second part of this blog post will seek to demonstrate that the unbridled flow of liberating moves around customary international law has come with great simplifications of the traditional theory which has always been more sophisticated than is currently assumed. The paradox is that easing the theory of customary international law and amplifying the argumentative platform it offers diminishes the authority that can possibly be created by this modern argumentative technique while simultaneously leaving the intellectual prison intact. In other words, behind the dance floor, the prison bars and the steel gates are left in place. Worse, the cells are now filled with new villains.

(To be continued in Part II).

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Jordan says

April 14, 2014

This is a delightful read, but so was the exchange between Alice and Humpty. I suspect that behind the metaphors there is a lurking state-oriented, rule-oriented positivist abhorrence of community law created through a process of participation in the shaping of practice and opinio juris, such as that identified by the IMT at Nuremberg as CIL. "Soft"? hardly.
In any event, there have always been actors other than the "state" with formal participatory roles ( ) Further, many types of actors particpate in the creation, expansion, contraction, invocation, application, reaffirmation, and termination of CIL norms. See
Are you opposed to this process and the evident general acceptance of CIL? Are you opposed to its primacy when it becomes jus cogens? Are you opposed to its use as background for interpretation of any treaty? Do you consider treaty meaning or content over time to be far less malleable? What sort of consequences might occur if CIL is relegated to what is merely "soft"? Before the ICC, in view of trends before the IMTs at Nuremberg and the Far East, the ICTY, and the ICTR?