International Court of Justice, ICJ, customary international law, conventional obligations, Silala waters dispute, Chile, Bolivia, international law, treaties, custom, State practice, opinio juris
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Abstract
The International Court of Justice (ICJ) judgment on the dispute concerning the status and use of the Silala waters between Chile and Bolivia clarifies the distinction between customary and conventional obligations in international law.
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[...] The States are not in agreement on the qualification of the customary norms applicable to the dispute, as well as their applicability. Thus, Articles 11 and 12 of the 1997 Convention are discussed, in order to determine whether they are customary and to determine their application in the event of a customary obligation. Referring to the theory of two elements, in what measures does the ICJ clarify the distinction between conventional obligations and customary obligations to determine the obligations of States? [...]
[...] Theopinio juris reflects an intentional element of States, which practice the rule in question because they think it is obligatory, or because they have the feeling that it should be. The ICJ uses the two-element theory to determine whether Article 11 of the 1997 Convention reflects customary international law. The application of the two-element theory to Articles 11 and 12 of the 1997 Convention In this judgment, the ICJ applies the two-element theory to determine the existence or non-existence of an international custom regarding Article 11 of the 1997 Convention. In fact, the Parties are not in agreement; Chile asserts the customary nature of the provision, unlike Bolivia. [...]
[...] The ICJ concludes that there is a rule that the obligation should be implemented if the measures are 'of a nature to produce prejudicial effects of a certain scope ». Thus, while the obligations are different, the ICJ forms a fairly general and vague rule on the condition for implementing the obligation. While the Court is aware that the requirements for notification and consultation set out are not the same, the jurisdiction holds that Article 12 of the Convention does not reflect a customary rule that 'would be more demanding than the general obligation to notify and consult as it emerges from its jurisprudence ». [...]
[...] Commentary on the text: ICJ, Dispute concerning the status and use of the waters of the Silala (Chile v. Bolivia), judgment, 1er December 2022: « Not only the work of the International Law Commission and the conventions resulting from it constitute a means of proof of customary law in areas where there is prior state practice, but also, codification can contribute to creating customary law, even when the rules stated in the codification convention are new. »1 Henri Torrione, law professor shows the interactions between international treaties and custom, stating that a treaty can give rise to a customary rule, and conversely, a treaty can codify a customary rule. [...]
[...] The ICJ therefore reiterates this argumentation, to conclude that in « in the absence of general practice and opinio juris supporting this thesis, the Court cannot conclude that Article 11 would be a reflection of customary international law. » The Court's jurisprudence therefore reiterates the traditional theory of two elements. In parallel, as regards Article 12, the Parties agree on « to consider it as reflecting customary international law ». The Court notes that Article 12 of the Convention corresponds to its jurisprudence « relating to procedural obligations incumbent on States under customary international law regarding transboundary damage ». Beyond knowing whether Article 12 is customary, the Court then asks which obligation applies to the Parties between Article 12 of the Convention or the Court's jurisprudence, the two seeming to be different. [...]
