A brief restatement of the facts is, however, desirable.
The Appellant, an Australian national visiting England, was the subject of a European Arrest Warrant issued by the Respondent, the Swedish criminal prosecution authority. As a consequence, the Appellant was arrested in England, and promptly challenged the validity of the warrant on various bases. His challenge was denied in the first instance before a District Judge, and then on appeal by the Divisional Court (Assange v Swedish Judicial Authority  EWHC 2849 (Admin)). He finally appealed to the Supreme Court on a single point, namely that s. 2(2) of the Extradition Act 2003 (UK) required that the warrant be issued by “a judicial authority”. The Appellant contended that the Respondent as a prosecutorial body was not ‘judicial’ in nature and accordingly, that the warrant was invalid. The Court was therefore required to determine the meaning of “judicial authority” as provided for in the Extradition Act and, more particularly, whether the Respondent fell within the definition so developed.
An additional layer of complexity, however, was added to the matter by the fact that the Extradition Act was not a solely municipal piece of legislation. Part 1 of the Act was passed to give effect to the Council Framework Decision on the European Arrest Warrant and Surrender Procedures between Member States of the European Union (the Framework Decision), which itself used the term “judicial authority” in a number of places. The meaning of “judicial authority” as it appeared in s.2(2) of the Extradition Act therefore depended on the meaning to be given to the term as it appeared in the Framework Decision. The Court, applying the Vienna Convention on the Law of Treaties (VCLT) – and particularly Article 31(3)(b) thereof, concerned with the subsequent practice of states – determined that a prosecutorial body could be considered a “judicial authority” for the purposes of the Framework Decision, and accordingly that the warrant was valid for the purposes of the Extradition Act ( UKSC 22, para 67 (Lord Phillips PSC), para 94 (Lord Walker JSC), paras 106-108 (Lord Kerr JSC), paras 130-1, 154, 171 (Lord Dyson JSC). Cf ibid, para 191 (Lady Hale), para 242 (Lord Mance)).
This conclusion, with respect, was incorrect as a matter of European and international law: VCLT Article 31(3)(b) cannot be legitimately used to support the Court’s interpretation of “judicial authority”. In the first place (to be considered in this post), the Court erred in applying VCLT Article 31(3)(b) to the Framework Decision as (a) the jurisprudence of the European Court of Justice (ECJ) demonstrates that court’s aversion to the use of subsequent practice as a tool of interpretation, (b) the Framework Decision is not a treaty, and (c) the ECJ has never applied the VCLT to secondary EU acts. In the second (to be considered in the next post), even if VCLT Article 31(3)(b) was applicable to the Framework Decision, the conditions for its application were not met in Assange.
Part 1: Non-applicability of the Vienna Convention on the Law of Treaties to the Framework Decision
The Supreme Court in Assange ignored the practice of the ECJ when it applied VCLT Article 31(3)(b) in interpreting the Framework Decision. It is true that the ECJ has affirmed that the customary international law of treaties forms part of the European legal order, and it generally follows the VCLT (implicitly or explicitly). However, despite the ECJ adhering to the general rule embodied in Article 31, it applies the principles embodied in the article in a “Community manner”, greatly emphasising the importance of the object and purpose rather than that of the literal meaning, and disregarding subsequent practice as a supplementary method of treaty interpretation.
A. The ECJ’s approach to subsequent practice
The ECJ has never explicitly relied on Article 31(3)(b) in its case law. As far as Community law is concerned, especially in relation to the EC Treaty, the Court does not accept arguments of subsequent practice. The Court has held that “mere practice” cannot change the treaty. Originally this approach applied only to the choice of legal basis for Community acts, but the Court extended it to the interpretation of the EC Treaty in Case C-327/91. In this case, between France and the Commission, France brought an action under the first paragraph of Article 173 of the EC Treaty and Article 33 of the European Coal and Steel Community (ECSC) Treaty for a declaration that the Agreement signed on 23 September 1991 by the Commission and the United States regarding the application of their competition laws was void. In interpreting Article 228 of the EC Treaty regarding the conclusion of agreements by the Community, the Court held that “a mere practice cannot override the provisions of the Treaty” (Case C-327/91, France v Commission,  ECR I-3641, para 36).
The Court affirmed this in Opinion 1/94. The Court, in interpreting Article 114 of the EC Treaty, reiterated that “the Court has consistently held that a mere practice of the Council cannot derogate from the rules laid down in the Treaty and cannot, therefore, create a precedent binding on Community institutions with regard to the correct legal basis (see Case 68/86 United Kingdom v Council  ECR 855, paragraph 24)”. In a later paragraph of the Opinion the Court concluded that institutional practice in relation to autonomous measures or external agreements adopted on the basis of Article 113 could not alter its conclusion (Opinion 1/94,  ECR, p. I-5267, paras 52, 61).
On the basis of these cases Kuijper correctly concludes that ‘“[s]ubsequent practice” as an aid to interpretation of treaty texts is seriously neglected and frankly rejected when interpreting the EC Treaty and the instruments based on it’ (Kuijper (1998) 25 LIEI (1998), 23). The Supreme Court in Assange did not enquire whether the VCLT Article 31(3)(b) would be applicable; it was just assumed it was, without any legal reasoning.
B. The secondary acts of the EU do not qualify as “treaties”
Article 2 of the VCLT provides that “(a) ‘treaty’ means an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation”. The instrument to be interpreted in Assange was the Council Framework Decision 2002/584/JHA of 13 June 2002 on the European Arrest Warrant and the Surrender Procedures between Member States. Framework decisions were pre-Lisbon legal instruments of the second pillar of the European Community created on the basis of Article 34 of the Amsterdam Treaty and used exclusively within the EU’s competences in police and judicial cooperation in criminal justice matters.
Article 34(2)(b) gave the Council the right to adopt framework decisions for the purpose of approximation of the laws and regulations of the member states. Framework decisions were created by the Council, an organ of an international organisation (the EU); the procedure for the adoption of a framework decision was different from the procedure of concluding a treaty; and there were no parties to the instrument as it was a unilateral act of the EU. For these reasons alone, framework decisions do not fall under the definition of “treaty” contained in Article 2 of the VCLT and, accordingly, the VCLT is not applicable to their interpretation. It is surprising that the Supreme Court failed to take into consideration the legal nature of the act in question and did not justify their decision to apply the VCLT in interpreting the Framework Decision.
C. The ECJ has never applied the VCLT to secondary acts
A survey of the judgments of the ECJ reveals that the Court has never referred to the VCLT in interpreting secondary acts of the EU. Instead, it refers to the “principles of interpretation”, the content of which becomes clear from an examination of its case law, and not from international law sources on treaty interpretation. In Foreningen the Court held that:
“It is common ground that Directive No 77/187 does not contain an express definition of the term ‘employee’. In order to establish its meaning it is necessary to apply generally recognized principles of interpretation by referring in the first place to the ordinary meaning to be attributed to that term in its context and by obtaining such guidance as may be derived from community texts and from concepts common to the legal systems of the member states”.
In Bosphorus the Court, interpreting a regulation, stated that it is evident from the ECJ’s case-law that “in interpreting a provision of Community law it is necessary to consider its wording, its context and its aims” (Case C-84/95, Bosphorus,  ECR I-3953, para 11). More recently, in Reliance Industries, the Court had to interpret both international agreements and EC anti-dumping and anti-subsidy regulations. In interpreting the former the Court stated that: “a treaty under international law […] must, in accordance with Article 31(1) of the Vienna Convention on the Laws of Treaties of 23 May 1969, ‘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’” and held that:
“That rule of interpretation corresponds to the rule applied by the Community judicature when called upon to interpret a provision of Community law. Thus, the Court of Justice has repeatedly held that, in interpreting a provision of Community law, it is necessary to consider its wording, its context and its aims” (Case T-45/06, Reliance Industries Ltd v Council of the European Union and Commission of the European Communities,  ECR II-02399, para 100).
The ECJ does not apply the VCLT to the interpretation of regulations; rather it applies a Community rule of interpretation, albeit one with a similar content to Article 31(1). Importantly, the Court does not refer to the entirety of Article 31, which would include subsidiary means of interpretation, in explaining the content of its interpretative rule.
The Supreme Court wrongly, and without any analysis, assumed that VCLT Article 31(3)(b) is applicable in the interpretation of secondary European acts such as the Framework Decision. It also neglected to look into the interpretative rules of the EU. The result was a fundamental mistake in the legal reasoning of the Court.