2. How to interpret an interpretive device

It might seem strange that a rule of interpretation could itself be in need of interpretation. How could an interpretive tool possibly guide the interpretive process if the guidance it provides is not immediately clear and ready for use? This problem might seem paradoxical. It has, however, frequently been present in the history of thought, as demonstrated by the famous old enquiry as to ‘Who guards the guardians?’ (Quis custodiet ipsos custodes?).

Nor is the paradox entirely unfamiliar in international law. During the United Nations Conference on the Law of Treaties, the Greek delegation observed that interpretation could not obey hard-and-fast legal rules. According to the Greek delegation, the explanation for this lies precisely in the fact that there is no answer to the question of how to interpret the rules of interpretation:

Though theoretically fascinating, the problem does not, however, seem to be as dramatic as the Greek delegation's comment might suggest. In fact, it is perfectly conceivable to apply the general rule of interpretation provided in the Vienna Convention to this rule itself. The reason for this is that most rules of treaty interpretation set forth in Article 31 of the Vienna Convention seem to be dictated by common sense. One could, for instance, hardly imagine a rule of interpretation according to which a treaty should be interpreted in bad faith, without any regard for its context, or its object and purpose.Footnote ⁷ A comment to this effect was in fact explicitly made during the debates within the International Law Commission on the draft rules of interpretation, when Roberto Ago stated that ‘if the parties agreed to interpret the treaty in another way, there was nothing to prevent them from doing so; but that would no doubt occur rarely, for those rules were eminently reasonable’.Footnote ⁸

Such an approach, which points to the self-referential nature of interpretive rules, is explicitly adopted in some national legislative acts.Footnote ⁹ One could also mention the guideline provisionally adopted by the International Law Commission for the determination of the object and purpose of the treaty. According to that guideline, ‘The object and purpose of the treaty is to be determined in good faith, taking account of the terms of the treaty in their context’.Footnote ¹⁰ It is clear that the guideline relies on the framework provided by Article 31(1) of the Vienna Convention, even though the provision in question in turn invites the interpreter to look to the object and purpose of the treaty to shed light on the ordinary meaning of the terms that the treaty contains. There seems, therefore, to be nothing revolutionary about the notion that Article 31(3)(c) is itself subject to the interpretive regime set forth in Article 31 of the Vienna Convention.

3. Why ‘the parties’ could not mean anything less than ‘all of the parties’

The application of Article 31 in order to clarify the meaning of Article 31(3)(c) helps us to better understand the ambiguous aspects of this provision. A good example is the term ‘the parties’ as used in the provision. There is some debate in the literature as to whether the term ‘the parties’ mentioned in Article 31(3)(c) refers to all the parties to the treaty under interpretation or only those who are in dispute.Footnote ¹¹ This issue has attracted much debate in the context of the interpretation of the WTO Agreements. Some authors have suggested that the term ‘the parties’ could be interpreted as referring to the contentious context, thus providing the WTO's dispute-settlement bodies with the opportunity to take into account the rules of a treaty applicable between the parties in dispute.Footnote ¹² This reading was defended in the Report of the International Law Commission's Study Group on Fragmentation of International Law,Footnote ¹³ but explicitly rejected by a WTO Panel in the EC-Biotech Products case in which the Convention on Biological Diversity and the Biosafety Protocol – instruments to which all WTO members were not parties – were invoked by the European Communities as sources of ‘relevant rules of international law applicable in the relations between the parties’.Footnote ¹⁴

The interpretation offered by the WTO Panel has been defended on a number of grounds ranging from the definition of parties in Article 2(g) of the Vienna ConventionFootnote ¹⁵ to the contextual arguments taken from the overall structure of Article 31(3).Footnote ¹⁶ However, few commentators seem to rely on the direct application of the interpretive regime of the Vienna Convention to interpret the term ‘the parties’ as referring to all of the parties to the treaty. It is our contention that the use of this interpretive regime confirms the accuracy of the reading offered by the WTO Panel in more straightforward terms. Two lines of inquiry could be followed to support this suggestion. First, throughout the Vienna Convention, the term ‘parties’ refers to the ‘parties’ to the treaty and, when the context of litigation is specifically intended, a textual specification is provided.Footnote ¹⁷ On the basis of this, one could argue that a case would need to be made in support of the idea that, in Article 31(3)(c), the meaning of the term ‘the parties’ differs from its ordinary meaning in the overall context of the Vienna Convention. It seems, therefore, that the question is one envisioned by Article 31(4). According to this provision, ‘A special meaning shall be given to a term if it is established that the parties so intended’. This means that proponents of the interpretation of ‘the parties’ as referring to ‘the parties in dispute’ bear the burden of proof of the special meaning as provided in Article 31(4). It would, however, be difficult to find any such proof, given that the Vienna Convention is obviously not confined to the context of litigation.Footnote ¹⁸

Second, the interpretation of ‘the parties’ as referring to the parties in dispute before a judicial body would run counter to the very raison d'être of the interpretive regime of the Vienna Convention. The logical assumption behind the Vienna interpretive regime is that there is one correct meaning for any treaty provision that is common to all the parties and that this meaning is the one obtained through the application of the rules of interpretation that the Vienna Convention provides. If the interpretation of a treaty comes to vary depending on the identity of those of the parties that are in dispute, then the whole point of the Vienna interpretive regime would be missed. Incidentally, such a result would hardly be a desirable outcome as far as the harmonization of the international legal order is concerned, considering that interpretations of a treaty in harmony with the rest of international law would come at the price of a fragmentation of the treaty itself. In this regard, it is far from convincing to contend that a treaty could well be subject to different interpretations by relying on the possibility of the inter se agreements ‘to modify multilateral treaties between certain of the parties only’ as provided in Article 41, on the differentiation of the treaty relationship by virtue of reservations as contemplated by Article 21, or on Article 30(4), which provides that different treaty regimes could apply to different parties, depending on whether or not they participate in the subsequent treaty on the same subject matter.Footnote ¹⁹ When these events occur, what is at issue is not the interpretation of the same treaty along different lines, but the modification of the treaty by the will of some parties. In other words, the very object of interpretation changes because of some acts accomplished to this effect by two or more parties, but not by the decision of the interpreter.

4. A structural limitation on the operation of Article 31(3)(c) in judicial settings

It is commonplace in international law that international judges are not in the same position as their domestic counterparts. The international judge is traditionally said to exist only because and to the extent that he is wanted.Footnote ²⁰ The spectacular development of international law since the end of the Second World War has in no way altered the fact that ‘no State can, without its consent, be compelled to submit its disputes with other States either to mediation or to arbitration, or to any other kind of pacific settlement’.Footnote ²¹

The relevance of such a state of affairs for the authority of international courts and tribunals lies not only in the fact that the jurisdiction of these bodies is always consent-based, but also in the limitation of the jus dicere power of international courts and tribunals – in other words, their power to say what the law is. Since this often neglected aspect of jurisdiction entails important consequences for the implementation of Article 31(3)(c), some clarification is in order.

The absence of centralized power structures on the international scene is a well-known reality in international society. One of the consequences of this situation is the power of auto-interpretationFootnote ²² held by states: states are judges in their own cases, each state having the power to determine for itself the content of its rights and obligations.Footnote ²³ This means that the judicial determination of the content of states’ rights and obligations can, as a matter of general international law, only occur as a result of a delegation on the part of states concerned. In other words, judicial pronouncements on a rule of international law produce legal consequences for states concerned not because they are made by a judicial body – they could equally be made by any other third party empowered to do so – but because those states delegate their potestas interpretandi to the international judge, renouncing this power on a general basis or on the occasion of the particular case submitted to the judge. Of course, as a matter of fact, judicial pronouncements produce effects well beyond individual cases. But this sociological fact has no bearing on the accuracy of the legal analysis along the lines just presented as a structural reality of international law.

This point can be illustrated by a well-known example. It is generally assumed and officially confirmed that the advisory opinions of the ICJ are not binding.Footnote ²⁴ This may come as a remarkable surprise if one confines one's analysis to the fact that an advisory opinion of the ICJ is as much grounded on legal materials as a judgment in a contentious case. How can an opinion grounded on international law be said to be ‘advisory’, but not mandatory as a matter of international law? The only satisfactory answer is that, while a contentious case implies a delegation of interpretive power on the part of states parties to the dispute, the advisory jurisdiction involves no such thing. Another relevant example to the same effect is Article 63(2) of the Statute of the ICJ, which provides that, outside the circle of the states in dispute, the interpretation of a multilateral treaty given in a judgment of the Court would be binding only on those of the parties that exercise their right of intervention. This shows that, as a matter of official doctrine, the authoritativeness of an interpretation is a function of legal ‘conventions’, without being automatically attached to an interpretation because of its judicial nature.

As acknowledged by one author, such limitations on the power of international tribunals to say what the law is are a matter of public order in international litigation.Footnote ²⁵ The judicial power to determine the meaning of the law is thus intimately linked to the jurisdiction of the international judge, as suggested by the very terminology used to refer to it (juris dictio).Footnote ²⁶

It cannot be disputed that Article 31(3)(c) is subject to such a structural limitation in judicial contexts. First, the limitation in question can be considered one of ‘inherent limitations' by which the judicial function in international law is ‘circumscribed’.Footnote ²⁷ Second, applying the interpretive rule contained in Article 31(3)(c) to this rule itself, one could argue that the limitation in question can be seen as a rule of general international law relevant for the purposes of Article 31(3)(c). It is true that, formally speaking, the rule in question is not applicable in the relations between the parties, but rather to an international tribunal. But it is equally true that a rule with such drastic consequences in terms of states’ potestas interpretandi can also be characterized as a rule applicable between parties.

Bearing this limitation in mind, it is important to clarify what kind of rules Article 31(3)(c) refers to. It is beyond question that rules of general international law are among those rules. The travaux préparatoires of the Vienna Convention provide ample evidence for the notion that rules of general international law are what many members of the International Law Commission had in mind while discussing Article 31(3)(c).Footnote ²⁸ Another piece of evidence can be found in the remarks made by the German representative in the Vienna Conference on the Law of Treaties. While the draft text submitted to the Conference did not specify that rules of general international law were what the text was referring to, the German representative asked ‘Why should only the rules of general international law applicable between the parties be taken into account?’.Footnote ²⁹

That being said, there is also support for the suggestion that the ‘rules of international law’ are not confined to general international law. First, some members of the International Law Commission explicitly supported this view.Footnote ³⁰ One can also posit that the specification ‘applicable between the parties’ makes more sense in the case of treaty law than in that of general international law, the latter being, by definition, applicable between the parties, with the possible exception of cases in which there is the problem of persistent objectionFootnote ³¹ or in which specific rules of general international law have been contracted out. Finally, the application of the interpretive regime of Article 31 supports the conclusion that rules of international law designate a broader category than general international law. One needs only to mention the ordinary meaning of ‘international law’ to see that treaty law is also contemplated by Article 31(3)(c).Footnote ³²

The fact that Article 31(3)(c) refers to the rules of general international as well as to those of treaty law applicable between the parties does not, however, imply that an international tribunal has a similar interpretive power with regard to these two categories of rules. It seems beyond dispute that an international tribunal has the power to construe general international law given that rules of general international law constitute the normative background of every treaty. One can say that this power is part of the inherent jurisdiction of every tribunal as recently defined by the Special Tribunal for Lebanon.Footnote ³³ However, one should also pay special attention to the fact that treaties are often, by definition, lex specialis with regard to general international law. As Richard Baxter once observed, ‘the very existence of the treaties may indicate that the parties had assumed duties to which they would not have been subject in the absence of agreement’.Footnote ³⁴ The conclusion that follows was clearly stated by the Permanent Court of International Justice: ‘A principle taken from general international law cannot be regarded as constituting an obligation contracted by [the parties] except in so far as it has been expressly or implicitly incorporated in the [treaty].’Footnote ³⁵ Bearing in mind the relationship between general law and special law, one could lay down the following presumption: whenever general international law is not explicitly or implicitly contracted out, it is subject to the juris dictio power of an international tribunal given the fact that every treaty is concluded against the background of general international law.Footnote ³⁶

The situation is altogether different where treaty law is concerned. Unless an extraneous treaty rule is subject to the jurisdiction of the tribunal, the latter does not have the power to say authoritatively what the law of the treaty in question is. Contrary to what some authors suggest,Footnote ³⁷ the fact that the applicable law is not limited by the contours of the jurisdiction does not alter the conclusion that the scope of applicable law that an international tribunal can authoritatively determine is closely linked to the scope of its jurisdiction. It is rare to see international tribunals, especially those specialized in specific areas of international law, empowered with the competence to settle a dispute on the basis of international law as a whole. The jurisdiction is often recognized with regard to a clearly specified law and, if this limitation is to have any meaning, it should mean that the law objectively applicable between the parties in dispute is not entirely subject to the judicial cognizance. That is why – to take one example among many – the ICJ was not able to have recourse to the rules set forth in multilateral treaties in the Nicaragua case,Footnote ³⁸ even though those rules were clearly part of the applicable law between the parties. In other words, the law objectively applicable between the parties in dispute is not judicially cognizable in its totality when the jurisdiction to consider the applicable law is limited. This is the case because the authority attached to the judicial determination of the meaning of law is a function of the jurisdiction of the tribunal.

5. An attempt at a meaningful reading of Article 31(3)(c)

The above observations might seem to suggest that Article 31(3)(c) does not have much utility. This conclusion should be resisted, for several reasons. To start with, with the caveats stated above, general international law is always the legal background of any treaty and, as such, subject to the implicit power of jus dicere of an international tribunal.

Second, the limitation applicable in judicial contexts has no relevance when states parties to a treaty themselves interpret their rights and obligations under that treaty. To paraphrase an observation made by Robert Jennings in a not-too-dissimilar context,Footnote ³⁹ it is perhaps only lawyers who could think that litigation is the only worthwhile aspect of the law. Since the operation of the Vienna Convention is obviously not confined to the judicial context, Article 31(3)(c) cannot be said to be of limited interest.

However, it remains to be seen what use can be made of Article 31(3)(c) in judicial contexts with regard to extraneous treaty rules applicable between the parties when the tribunal has no jurisdiction in relation to those rules. It is not entirely clear that the principle of effet utile would require that a treaty provision should be operational in the same way in every conceivable situation. It is nonetheless reasonably safe to assume that to read Article 31(3)(c) as categorically prohibiting judges from taking into account rules contained in a treaty that is not technically part of the applicable law in relation to which they have jurisdiction would deprive the provision of much of its effect.

Several scenarios can be considered in this regard. When the rule contained in the other treaty has been interpreted by the parties in an interpretive agreement or when the meaning of the rule has been otherwise authoritatively established, such as through a consistent practice of a treaty-monitoring body if there is one, the tribunal could arguably take notice of the rule so interpreted without risking the accusation of overstepping its power of jus dicere.

If there is neither interpretive agreement nor any other authoritatively established interpretation, a case could be made to support the suggestion that the tribunal could take into account the rule of the other treaty if this means only taking notice of the ordinary meaning of the terms through which the rule is formulated. This condition is crucially important for the tribunal to remain within the limits of its power of jus dicere. If the ordinary meaning of the relevant terms of the other treaty is not clear and an in-depth investigation into the object and purpose, the subsequent practice, or the travaux préparatoires is required, the tribunal could hardly engage in such an effort, for doing so would be tantamount to determining the meaning of the rule but not taking notice of it – a power that the tribunal does not possess in our hypothetical case because of ‘the jurisdictional restraints on [its] freedom of treaty interpretation, given the consensual nature of [its] jurisdiction’.Footnote ⁴⁰

Whatever the scenario, it seems reasonable to assume that the rule of the other treaty could only be used as an interpretive working presumption to be confirmed by the ‘internal materials’ of the treaty under interpretation itself. If the rule in question is used not as a working hypothesis to be confirmed by the internal elements of the treaty under interpretation, but as a decisive factor for selecting a particular interpretation, the tribunal would overstep its authority, since the latter does not include the power to decide what the true meaning of the rule contained in the other treaty is.

This last point is also confirmed by the structure of Article 31 as it is interpreted in international practice. It is true that the International Law Commission did not mean to establish any hierarchy among different elements of this article.Footnote ⁴¹ As the Special Rapporteur, Sir Humphrey Waldock, put it in his commentary, the very fact that the provision in question is entitled ‘General Rule of Interpretation’ and not ‘General Rules of Interpretation’ suggests that the interpretive process guided by this provision is to be seen as a single process involving all the various components it contains.Footnote ⁴² That being said, it is also clear that Article 31 implies what the Special Rapporteur termed ‘a logical order’.Footnote ⁴³ Despite the unity of the interpretive process suggested by the International Law Commission, practice shows that paragraph 1 of Article 31 enjoys an undeniable priority in the sense that the basic rule seems to be that ‘Interpretation must be based above all upon the text of the treaty’.Footnote ⁴⁴ The proposed reading of Article 31(3)(c) would thus be in line with the general philosophy of Article 31, which is dominated by the ‘ordinary-meaning’ approach.

This, however, raises a question about the possible added value of Article 31(3)(c) given that extraneous instruments are used in practice on the basis of Article 31(1). By way of an example, one could mention the US-Shrimps case, in which the Appellate Body of the WTO interpreted the phrase ‘exhaustible natural resources’ employed in Article XX(g) of the GATT in light of some environmental treaties that were not binding on all the members of the WTO in an attempt to determine the ordinary meaning of the term ‘exhaustible natural resources’ – in other words, using the interpretive device contained in Article 31(1).Footnote ⁴⁵ The latter provision might seem even more attractive given that the limitation related to the identity of the parties applicable in the context of Article 31(3)(c) has no relevance here: recourse may be had to other treaties merely to clarify the ordinary meaning of the provision under interpretation in light of what are considered to be relevant indicia extracted from extraneous legal materials. One could therefore wonder what Article 31(3)(c) could possibly add if the option of taking into account extraneous rules is already available on the basis of Article 31(1).

A possible answer could be that, while Article 31(1) does not mandate the use of extraneous materials, Article 31(3)(c) is part of the ‘common disciplines [imposed] upon treaty interpreters’.Footnote ⁴⁶ In other words, Article 31(3)(c) contains a mandatory disciplining rule whose use is not left to the discretion of the interpreter when the conditions of its application are met.Footnote ⁴⁷ In addition, focusing specifically on extraneous rules applicable between parties, Article 31(3)(c) provides room for the application of the presumption of non-conflict.Footnote ⁴⁸ In this regard, it is interesting to note that the rule according to which ‘A text emanating from a Government must, in principle, be interpreted as producing and as intended to produce effects in accordance with existing law and not in violation of it’Footnote ⁴⁹ was qualified by the ICJ as ‘a rule of interpretation’. Whenever it seems possible, an international tribunal should thus follow the assumption that the parties to the treaty did not want to undertake conflicting obligations.Footnote ⁵⁰ It could be argued that the presumption of non-conflict is a logical implication of the presumption of good faith: responsible governments are thought to take special care to avoid any conflict between their different obligations and one cannot presume that, in a particular case, they have not done so.Footnote ⁵¹ By pointing to the extraneous rules, Article 31(3)(c) could, thus, be considered as inviting the interpreter to take the presumption of non-conflict seriously and to make every reasonable effort to give it a meaningful effect. One should, however, bear in mind that the primary purpose of Article 31(3)(c) is not to bring coherence to the world of international legal rules, but to offer interpretive guidance. The very fact that the norms of conflict resolution are offered in Article 30 shows that the main task of Article 31(3)(c) is not to provide a solution to conflicts between different rules of international law. Even the assumption of non-conflict could not help to avoid conflicts when the provision under interpretation and the extraneous rule are irreconcilable.