The Function of Principles of Treaty Interpretation
As Jan suggested at the end of his post, it seems that the broader question underlying our debate is how principles of treaty interpretation are used to empower international courts and tribunals and what the limits are of that function.
On interpretation as a rule-governed activity, it seems that we all approach Articles 31 to 33 VCLT as principles rather than rules, despite the fact that they are formally treaty law reflecting customary international law on the matter. But it seems that this is not necessarily (anymore) the common perception of many commentators on treaty interpretation. This impression is based on many discussions and writings about the interpretation Article 31(3)(c) VCLT, characterized by a high-level of technicality and very much the belief that this is ‘a rule’. I’ve written elsewhere that Article 31(3)(c) VCLT is perhaps the only mistake in Articles 31 to 33 VCLT, in the sense that the value and function of the principle of harmonious interpretation might have been better served had the ILC decided not to codify the principle, for the same reasons why they decided not to codify the principle of effectiveness (which is widely applied, especially by courts and tribunals operating within an institutional context and interpreting continuously the same treaty text). The ILC made it clear that it did not intend to ‘exhaustively’ codify the matter of interpretation; it merely intended to state the basic principles based on the available practice at that time.
On the function of principles of treaty interpretation, I still think that they, on the one hand, help guide and structure the reasoning process, but, on the other hand, also help to justify the conclusion a court or tribunal reaches on the meaning of the treaty (to some extent, for whatever reason). They help make this conclusion acceptable for its audience (which introduces another contextual element). But their role cannot entirely be reduced to merely one of post hoc rationalization.
As international courts and tribunals multiply and judicial review of States’ measures and laws in the light of their international obligations increases, Articles 31 to 33 VCLT become more attractive. They seem to offer some level of objectivity, making the applicable standard of review more acceptable – especially at the earlier stage of a court’s existence when it might still be developing that standard of review (depending on the applicable procedural rules). Perhaps this is the start of a complex answer to Jan’s question.
I should also clarify that my earlier comment on the mild trend from formalism to informalism in justifying treaty interpretation in the WTO applies to the Appellate Body. It appears that panels have yet to fully respond to this development.