Is Evolutionary Interpretation Only A Matter of Finding the Parties’ Intentions?

The main thesis in Eirik Bjorge’s The Evolutionary Interpretation of Treaties is that evolutionary interpretation depends on the intention of the parties to a treaty and results from applying Articles 31 to 33 of the 1969 Vienna Convention on the Law of Treaties (‘Vienna Convention’).

Few would probably dispute that treaty interpretation always involves the intention of the parties. However, the debate – to which this monograph unquestionably is a valuable contribution – continues on where that intention is to be found. Is the controlling element the text of a treaty, its object and purpose (in whatever manner that might be established), its origins or some other feature? It would appear that there continue to be many perspectives on what the concept of the intention of the parties means and where it can (or should) be found.

Eirik Bjorge argues – in an intensely researched and reasoned manner showing deep familiarity with the origins of established views of methods of interpretation and the case-law supporting one or another view – that the basis of evolutionary interpretation can be all of these elements as long as they demonstrate the parties’ intentions. In so doing, he also elaborates in considerable detail on more or less related topics such as fragmented methods of interpretation and the merits of theoretical debates on interpretation. He approaches the concept of the parties’ intentions from, what appears to be, a strictly objective perspective according to which that intention can be found based on a methodological approach as commanded by customary principles of treaty interpretation, in particular Articles 31 to 33 of the Vienna Convention.

It is undoubtedly true that all of these elements might be relevant to an interpreter’s choice of whether or not it is necessary to interpret a treaty term or phrase in a manner that takes account of either legal or factual developments subsequent to a treaty’s conclusion. Thus, I do not take issue with the proposition that evolutionary interpretation is not a separate method of interpretation but rather can result from applying the principles codified in Articles 31 to 33 of the Vienna Convention. However, it appears to me that that those elements are not necessarily exclusive in controlling the decision of, in particular, an international court or tribunal, to interpret treaty terms or phrases in a manner that takes account of developments, whether or not specifically tied to the treaty being interpreted, that were not known to the treaty drafters at the time of the treaty’s conclusion.

In essence, at the time of a treaty’s conclusion or subsequent thereto, parties can choose to have that treaty interpreted in the light of later developments either by making that choice explicit in the treaty itself or in a later agreement (which might appear from applying the treaty in a particular manner). Each of these instances of what could be coined ‘evolutionary interpretation’ finds support in the Vienna Convention (see, for example, ordinary meaning and possibly special meaning, subsequent practice, subsequent agreement).

Other parts of Articles 31 to 33 of the Vienna Convention may also justify such an interpretation where that choice of the parties to a treaty is less easy to ascertain. For example, in so far as Article 31(3)(c) of the Vienna Convention is to be read as referring also to relevant rules of international law that emerge subsequent to the conclusion of the treaty, it might be that the parties’ decision to conclude an agreement that is to be governed by the law of treaties justifies, where relevant, evolutionary interpretation.

Yet, where an international court or tribunal must interpret a treaty in the light of general principles of law and apply those together with that treaty, the so-called intention of the parties might not necessarily be reflected solely in the text being interpreted but might need to be found elsewhere. Or, it might be that the parties are presumed to have intended a treaty to remain effective over time, especially where it is concluded for an indefinite period. In such circumstances, it would appear that, whilst it might very well be possible to tie evolutionary interpretation to the intention of the parties and, directly or indirectly, to Articles 31 and 32 of the Vienna Convention (and, as Eirik Bjorge’s monograph very usefully illustrates, those ties might be close or remote), the decision of international courts and tribunals to interpret a treaty in that manner also depends on the context in which they exercise their interpretive mandate. It would appear that evolutionary interpretation is not exclusively a matter of determining the intention of the parties.

Whether it is a matter of style or method of interpretive reasoning, the fact is that international courts and tribunals active in treaty interpretation and application (and using Articles 31 to 33 of the Vienna Convention) do not always make the same interpretive choices including as regards whether or not to take account of developments subsequent to a treaty’s conclusion. In a related context, Eirik Bjorge rightly asks how much evolutionary interpretation can be accepted before interpretation extends beyond the bounds of the intention of the parties. Yet, it seems to me that that question cannot be resolved entirely by relying solely on the concept of the parties’ intentions.

Elements outside what is codified in Articles 31 to 33 of the Vienna Convention also control interpretive choices. This is not a novel proposition. International courts and tribunals have always produced case-law within a specific context (whether or not institutional) and against a historical background, both of which affect what is considered to be acceptable and justified in terms of judicial interpretation in the context of a particular dispute submitted for adjudication by a third party. The interpretive practices of, for example, the World Trade Organization (‘WTO’) dispute settlement bodies or the Court of Justice of the European Union are deeply rooted in the features of the legal systems created by each organisation and the respective (often evolving) roles of each adjudicator therein as well as their origins.

I therefore have some reservations regarding a thesis that establishes the acceptability of and justification for evolutionary interpretation entirely on the notion of the intention of the parties as apparent from the application of Articles 31 to 33 of the Vienna Convention. I do not consider that the matter can be simplified in this manner. Despite the function of those provisions as the basis of evolutionary and other approaches to interpretation, international courts and tribunals exercise a certain degree of discretion (in a defined context and against a known historical background) in deciding to rely on those elements and possibly, based thereon, identify or (re)construct the intention of the parties.

Factors explaining how that discretion is exercised are relevant too in understanding the reasons for evolutionary interpretation. It is not particularly revealing to state that every interpretation of a text with authority as law is to start with the wording of that text because that text is the result of the consensus reached. That position does not resolve, for example, how to proceed in practice from one element to another in every case (taking into account the content and the logic of Articles 31 to 33). Nor does it help to explain how other factors (mostly) unrelated to the parties’ intention might be relevant. One example of such a factor is the possibility of treaty amendment or authoritative interpretations: rigidity in that regard might make it more acceptable for international courts and tribunals to ‘update’ the treaty so as to retain its relevance and thus effectiveness. Another is the function of an international court or tribunal in a wider institutional architecture, which might include separate entities with (quasi) legislative powers separate from the treaty-making powers of the drafters of the treaties establishing those entities. These are just a few of the factors that might also inform the choice of whether or not it is justified to take into account factual and legal developments subsequent to a treaty’s conclusion in interpreting it.