The Utility and Limits of Canons of Construction in Public International Law

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Murphy, Sean D.
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This draft chapter, for a volume that considers canons of construction and other interpretive principles in public international law, considers the utility and limits of such canons, drawing in part upon lessons learned from schools of American jurisprudence (formalism, realism, pragmatism) with respect to statutory interpretation. In international law, there are certain obligatory canons of construction that have been expressly incorporated in Articles 31 and 32 of the Vienna Convention on the Law of Treaties. These canons are essential elements of the interpretive process; while in any given context, one or the other of these elements might be favored, they are all to be “thrown into the crucible” in order to arrive at a proper interpretation.By contrast, other canons of construction – such as “effet utile,” “ex abundante cautela,” or “in dubio mitius” – are regarded as less essential to the interpretive process, and hence of more limited value. They certainly should not be approached as providing a mechanical or decisive means for resolving cases, given the likely ability to pair any given canon with another canon that calls for a different outcome. Indeed, the invocation of a canon as requiring a particular outcome may be an attempt to mask with legal jargon the interpreter’s own policy preference. Even when invoked simply as an interpretive aide, such canons must be used with caution, taking full account of the context at issue. Over time, perhaps there will develop within international law a better understanding (if not theory) for when it is that such canons should be employed, making their use more consistent and legitimate.In the meantime, such canons have been found useful in international discourse, and hence are referred to and relied upon. A canon might provide assistance to an interpreter as a non-obligatory guide for how best to approach analyzing certain elements of Vienna Convention Article 31, such as understanding the context of a treaty provision. If application of the elements of Article 31 have led to an interpretive outcome that is problematic, a canon might provide an alternative path of reasoning, of the kind envisaged in Article 32, perhaps by suggesting a general approach for harmonizing the diverse system of international law. Indeed, since the canons might be viewed as expressing an interpretive code understood within the international legal community, a canon might help in divining what was likely intended by the drafters of a treaty (or of a unilateral declaration). In any event, at a minimum, a canon can serve as one tool in the international lawyer’s toolkit, providing a simple way of expressing a complex logical claim, even if susceptible to rebuttal by an opposing logical claim.