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Induction, Assertion and the Limits of the Existing Methodologies to Identify Customary International Law

Published on December 2, 2015        Author: 
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Professor Talmon’s article on the methodologies employed by the International Court of Justice to ascertain custom is as important as it is timely now that the International Law Commission is advancing with its study on the identification of customary international law. To contribute to the debate, I propose to elaborate on a crucial question that the piece raises. Why is it that the Court so often resorts to ‘asserting’ customary international law instead of providing more robust reasoning to back up the rules that it identifies? Though the precise reasons why the Court takes the approach it does are a matter for speculation, I suspect that this has to do with limitations that are inherent to the standard methodology to establish custom (the ‘inductive method’, to use Professor Talmon’s terminology), in the shaping of which the Court itself has played a large part.

As Professor Talmon suggests, systemic reasoning – argument by principle and argument by analogy – has been a major catalyst for development in international law, filling gaps that would be left behind if the inductive method were applied. Yet, the inductive method is the best accepted methodology to identify custom insofar as it encapsulates the prevailing view as to what is required by the ‘rule of recognition’ of international law.

The problem with that ‘rule of recognition’ is that it does not allow us to reach any firm conclusions as to the existence of particular rules of custom. That becomes clear when one dissects the inductive method as defined and applied by the International Court. Read the rest of this entry…