Interpretation of International Uniform Law
1. Fundamental issues of interpretation and application of international uniform law
In order to promote greater legal certainty through the international unification of laws, the mere adoption of conventions on uniform law is insufficient. It is also necessary to ensure the uniform application and interpretation of such conventions by the courts. Although legal scholars and courts do not dispute the necessity of uniform application and interpretation, legal practice shows a clear homeward trend that is likely to endanger the project of legal unification. Of the factors which are crucial to achieving uniform application and interpretation, three stand out in particular. First, an autonomous definition of legal terms is required that is not overly infused with preconceptions imported from the respective jurist’s domestic legal education. Secondly, the autonomous meaning of terms ought not to be discerned through application of domestic legal methodology. Instead, the interpretation must be found through an international, autonomous methodology. Thirdly, international uniform application of conventions requires that courts pay due regard to the findings of other countries’ courts. Article 7(1) of the CISG, as well as similar provisions in other conventions, oblige contracting states and their courts to act accordingly. However, considering foreign courts’ rulings not only requires the willingness of domestic courts to do so, but also the access to foreign judgments and the ability to understand them.
As to uniform private law conventions (regarding the interpretation of Union law see: interpretation of EU law), a dichotomy in the nature of these conventions affects the choice of method of interpretation. While these conventions aim at governing the legal relations between private persons, the source of law is an international treaty, obliging contracting states to harmonize their respective laws. Due to the lack of an authoritative international judiciary, it is left to domestic courts to rule on these conventions. Moreover, these courts must obey their respective constitutional provisions on the relationship of public international law and domestic law, which may significantly influence the interpretation of conventions.
2. Applicable rules of interpretation
Before the entry into force of the Vienna Convention on the Law of Treaties (VCLT), legal scholarship disagreed as to whether the public international law rules on the interpretation of treaties could apply to uniform law conventions. However, after the VCLT (which does not exclude uniform law conventions) entered into force, the applicability of Arts 31 to 33 of the VCLT is now beyond serious challenge. Even where the Vienna Convention itself is not applicable due to its limited temporal scope (see Art 4 VCLT), its rules on interpretation apply as part of customary international law, as the International Court of Justice has confirmed (see Oil Platforms (Islamic Republic of Iran v United States of America), Preliminary Objection, Judgment  ICJ 803 para 23).
The criticism regarding the application of public international law rules on the interpretation of treaties is founded on the argument that these rules are addressed to legal relations between states, but not between individuals. The former would be governed by the sovereign will of states, the latter by the freedom of contract. The subjective and narrow interpretation oriented at the sovereign will of states would endanger the aim of uniform law conventions, ie the creation of legal certainty in international commercial relations. Instead, a more objective understanding would be required. The rules of public international law should apply only when interpreting the concluding provisions that are directly aimed at states.
Even in the hypothetical absence of the VCLT, this criticism must be emphatically rejected. Those who oppose VCLT’s application argue in favour of canons of construction yet to be developed by legal scholarship. It is questionable whether this method of interpretation de lege ferenda serves legal certainty. Though public international law rules on interpretation are indeed not suitable for contracts between private individuals, it is the uniform law treaty and not the contract whose interpretation is in question here. In addition, the VCLT does not adhere to the distinction between contractual treaties and law-making treaties that sometimes appeared in international legal scholarship before the adoption of the VCLT. Instead, Art 31(1) VCLT gives preference to the objective literal meaning over the subjective will of the parties as evidenced in the travaux préparatoires. VCLT rules on interpretation and resolution of conflicts between conventions are thus not only pertinent and applicable, but also widely accepted by courts in practice. However, it must be admitted that the applicability of the VCLT to many different types of treaties necessitates a certain flexibility which may give rise to conflicts with the interest in legal certainty. Nevertheless, the VCLT offers a framework upon which legal scholarship can further build.
3. Rules on the interpretation of treaties and their application to uniform private law conventions
According to Art 31(1) VCLT, a treaty ‘shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose’. By adopting textual, contextual, and also purposive methods of construction, the VCLT takes an objective approach. As Art 32 VCLT makes clear, the original intent of the parties as reflected by the travaux préparatoires is only accepted as a supplementary means of interpretation when the methods under Art 31(1) leave the meaning ambiguous or obscure, or lead to a result which is manifestly absurd or unreasonable.
a) Textual interpretation
The starting point for treaty interpretation according to the Vienna Convention is the ordinary meaning of the treaty’s terms at the time of its conclusion, unless the parties intended, per Art 31(4) VCLT, that a special meaning should be given to a term. However, even the determination of the ordinary meaning can be difficult in the case of a multilingual convention. Though Art 33 VCLT provides for some rules on the treatment of multilingual treaties, it cannot entirely solve problems arising from the use of several languages for the same text. If a treaty has been authenticated in two or more languages, the text in each language is equally official entailing a presumption that the terms of the treaty have the same meaning in each. If, nevertheless, ambiguities remain and cannot be eliminated by adherence to Arts 31 and 32 VCLT, an interpretation in the light of the treaty’s object and purpose shall be decisive. Interpretation is by no means limited to the lowest common denominator for all authentic textual versions. In the case of divergent meanings, it seems advisable to choose the text that best corresponds with the treaty’s object and purpose. Despite some argument in legal scholarship before the adoption of the Vienna Convention, Art 33 VCLT does not privilege the languages that were used in drafting. Nevertheless, the drafting languages become determinative when the travaux préparatoires are consulted as a supplementary means of interpretation.
However, these prescriptions must be confined as far as it concerns the application of uniform law conventions in domestic courts—their primary field of application. The practitioner in general will neither be able nor competent to perform a comparison of all authenticated texts. Instead, he will rely on the authenticated text version in his national language, or even a mere official translation supplied by his government if no authenticated text version in his national language exists, even though the latter has no binding value under international law. To the extent that divergences exist between these texts, domestic courts may—depending on the mode of incorporation of international treaties into domestic law under their respective constitutions—be obliged to apply the official text version in their respective national language, thereby breaching international law. Even where the constitution prescribes an interpretation of domestic law in the light of international law, textual divergences will not be evident to the judge. Consequently it remains for legal scholarship to assist and clarify the interpretation of uniform law conventions.
b) Contextual interpretation
Article 31(2) and (3) of the VCLT further clarifies the meaning of ‘context’ as mentioned in para 1 of Art 31. In addition to the text of the treaty, including its preamble and annexes, para 2 additionally incorporates interpretative agreements or declarations made by one or more state parties. When considering interpretive declarations by the parties, it is necessary, however, to bear in mind the thin line separating interpretive declarations and reservations. Paragraph 3 enlarges the scope of materials to be used in contextual interpretation to a) specific (even informal) agreements the parties concluded subsequently with regard to the treaty, b) to the subsequent practice in the application of the treaty, and c) any relevant rules of international law applicable in the relations between the parties. Rules of international law in this sense comprise treaties, customary law and general principles of law, but not non-binding restatements. This provision thus offers at least to a certain extent a means to resolve terminological inconsistencies between different conventions (see 4. below). As the application of uniform law by courts is also part of the parties’ subsequent practice in the sense of Art 31(3)(b) VCLT, a consistent application by courts can also become relevant for interpretation, obviating the need for recourse to provisions like Art 7(1) CISG. Nonetheless, it cannot be denied that subsections (a) and (b) of Art 31(3) have a certain subjective connotation, which is undesirable for the purpose of uniform law since the boundary between interpretation of a treaty and its revision is likely to be blurred.
c) Interpretation consistent with aims and purposes
Interpretation in the light of the convention’s objective and purpose is of utmost importance with respect to uniform law conventions. Although Art 31(1) VCLT only mentions the treaty as a whole, it also applies to the treaty’s individual provisions that must be read in the light of their relation to the whole treaty. According to the International Law Commission, the purpose of a given rule must be found within the parameters set by the plain meaning of its terms. Despite this strict textual approach, some international legal scholars endorse a more extensive or dynamic interpretation, especially for law-making treaties (and therefore, inter alia, uniform law conventions), that can be similarly found in European Union law. But examples also exist in case decisions, like the famous Fothergill v Monarch Airlines judgment (House of Lords  2 All ER 696) in which the court rejected on the basis of purposive considerations a possible result under a strict textual construction. Indeed—considering the difficulty of the revision of uniform instruments once they are adopted—a more dynamic interpretation would facilitate constant adjustment to changing economic needs and social values. But one should not forget that one would at the same time open up a wide discretion for judges, thus endangering the uniformity of treaty application. In addition, the adjustment to existing needs and values would face difficulties if the uniform instrument itself only reflects a minimum consensus among contracting states. Nevertheless, whether the wording is unambiguous or not is a question of degree and not to be assessed by a simple ‘yes’ or ‘no’. Thus, whether a purposive argument can outweigh a reasonably precise plain meaning depends on the importance of the particular objective at issue.
d) Historical interpretation
Although Art 32 VCLT stipulates that preparatory works and the circumstances of the treaty’s conclusion are only a supplementary means of interpretation, recourse to the travaux préparatoires actually plays an important role for the interpretation of uniform law conventions. This paradox, however, cannot be gainsaid insofar as the notion of ambiguity or obscurity in Art 32(a) VCLT is itself quite ambiguous. Compared to domestic legislative materials like records of parliamentary debates, whose interpretive value is doubtful at times, the quality of preparatory works published by the drafting organization generally gives a better clue as to the ‘correct’ understanding of the convention. Nonetheless, a textual interpretation that is buttressed by contextual and purposive arguments can hardly be rebutted by invocation of the parties’ original intent as reflected in the travaux préparatoires. Even if recourse is made to the preparatory papers for an interpretation based on historical considerations, the result must be, to some extent, based on an interpretation consistent with Art 31 VCLT.
4. Additional methods and maxims of interpretation
International legal scholarship has suggested additional means of interpretation such as comparative interpretation for uniform law conventions. Though the Vienna Convention does not refer to them, they are not necessarily incompatible. Moreover, they can be used at least to a certain extent within the frame set by the above-mentioned canons.
Several authors call for an interpretation that considers the use of terms in the context of the respective convention as well as in other similar conventions. The terminology in a whole field of uniform private law would be thereby harmonized, thus promoting the uniformity of application. Article 31(3)(c) VCLT is amenable to this approach, as long as the resulting interpretation is buttressed by context as well as object and purpose. However, this approach would require that all contracting states are also parties to the other conventions containing the same terminology. If the drafters intended to refer to the terminology of other conventions, this intent may be considered in the light of a historical interpretation to the extent permitted by Art 32 VCLT.
It remains unsettled in legal writing the extent to which comparative law may itself furnish a separate canon of interpretation. It has been argued that comparative legal analysis helps to fix the reading of treaty provisions in the varying contexts of different domestic legal systems. Moreover, comparative analysis helps to identify, among all the possible solutions in domestic legal systems, the ‘best’ one or at least a solution that is common, and thus acceptable, to all contracting states. In general, extensive comparative legal reports are submitted during the drafting process of a convention, forming a part of the travaux préparatoires in the sense of Art 32 VCLT. Moreover, by its functional character, legal comparison helps to discern the underlying (social) conflict that the convention’s rule addresses, thereby elucidating its object and purpose. But even in the case of identical wording, the necessity of an autonomous interpretation necessarily excludes automatically transferring findings regarding national law to uniform law conventions. Although comparative studies are therefore somewhat useful in the interpretive process, one should not forget that courts are generally not in a position to base their judgments on extensive comparative studies.
Legal maxims, like lex specialis or—in the case of subsequent revision—lex posterior, can apply when interpreting the same convention. Other legal maxims customary to some domestic legal systems, like expressio unius, argumentum e contrario, as well as general principles of logic are in conformity with the Vienna Convention. However, as to the former it is imperative to recall that they lack the mandatory character as found in some domestic legal systems. Their role is merely limited to arguments that can be referenced in systematic and purposive reasoning. The applicability of public international legal maxims, like in dubio pro mitius, or contra proferentem, to law-making treaties, and thus uniform law conventions, remains contested insofar as their existence is accepted at all.
5. Gap-filling and analogical reasoning
While more recent conventions provide rules for filling gaps within the respective conventions themselves (see Art 7(2) CISG), the extent to which gap-filling is permissible as to older conventions remains unsettled. Some authors reject the use of analogies in public international law founded upon sovereignty. However, one might wonder whether arguments based on the sovereign will of states are pertinent insofar as they concern uniform law conventions. In general, efforts to revise unsatisfactory conventions fail not because of the contentious positions of the contracting parties, but rather because of a lack of interest on the part of their respective domestic policymakers. Otherwise, fundamental notions of justice, as well as the guarantee of uniform autonomous interpretation (instead of recourse to the respective applicable domestic law) speak in favour of gap-filling by the judge. Despite its merits, the admissibility of analogical reasoning varies widely among domestic legal systems. Therefore, it remains unclear as to which gaps in international conventions are amenable to the judicial use of analogical reasoning.
6. Conflict of conventions
As a large number of conventions govern similar subjects, there is potential for conflict among these conventions. When conflicts arise, they diminish legal certainty, thereby endangering the whole project of legal unification. The Vienna Convention offers limited help. Insofar as the parties do not themselves provide for a solution (eg by including compatibility clauses), the lex posterior principle as enshrined in Art 30(2) and (3) VCLT will govern the relationship. Nevertheless, ‘mutual rights and obligations’ under the older treaty remain valid in relation to states that did not join the more recent treaty. As far as they concern uniform law conventions that are not based on strict reciprocity, conflicting obligations must co-exist. If a state becomes a party to two incompatible uniform law conventions, it will necessarily breach its obligations under public international law if this conflict cannot be solved by interpretation. In that event, the judge himself must decide which convention to apply and which to ignore. Legal scholarship has tried to develop criteria to address this issue: (1) the more efficient convention should prevail over the less efficient; and (2) the more specific convention should prevail over the more general. Although this question remains unsettled, it is largely accepted that substantive uniform law conventions take priority over conventions on the conflict of laws. Purposive considerations and Art 31(3)(c) VCLT support this result.
International Law Commission, ‘Report of the International Law Commission on its eighteenth session, UN Doc A/6309/Rev 1’ [1966-II] Yearbook of the International Law Commission 217; René David, ‘The International Unification of Private Law’ in IECL II (1971) ch 5, paras 247 ff; FA Mann, ‘Uniform Statutes in English Law’ (1983) 99 LQR 377; Rudolf Bernhardt, ‘Interpretation in International Law’ in Rudolf Bernhardt (ed), Encyclopedia of Public International Law, vol II (1995) 1418; Michael P Van Alstine, ‘Dynamic Treaty Interpretation’ (1998) 146 University of Pennsylvania Law Review 687; Christophe Bernasconi, ‘Rules of Interpretation Applicable to Private International Law Treaties: An Overview’ in Wybo Heere (ed), International Law and the Hague’s 750th Anniversary (1999) 139; Franco Ferrari, ‘Interpretation of the Convention and Gap-filling: Article 7’ in Franco Ferrari, Harry Flechtner and Ronald A Brand (eds), The Draft UNCITRAL Digest and Beyond (2004) 138; Jürgen Basedow, ‘Uniform Private Law Conventions and the Law of Treaties’  Uniform Law Review 731; Ulf Linderfalk, On the Interpretation of Treaties (2007).