In his Fourth Report on the Identification of Customary International Law (2016), Special Rapporteur Sir Michael Wood confirmed that ‘[i]n certain cases, the practice of international organizations also contributes to the expression, or creation, of rules of customary international law’. That the practice of international organizations can be relevant when identifying customary international law is relatively uncontroversial. The issue that is more debated is the extent to which the practice of international organizations as such may contribute to the development of customary international law. Using examples from the European Union's treaty practice and from the Court of Justice of the European Union, this article argues that international organizations may contribute to such practice, not only by representing the collective will of States, but as autonomous actors in their own right.
1 ILC, Fourth Report on Identification of Customary International Law by Michael Wood, Special Rapporteur, International Law Commission 68th Session, Geneva, (2 May–10 June and 4 July–12 August 2016) UN Doc A/CN.4/695 (‘Fourth Report’).
2 ILC, Third Report on Identification of Customary International Law by Michael Wood, Special Rapporteur, International Law Commission 67th Session, Geneva, (4 May–5 June and 6 July–7 August 2015) Un Doc A/CN.4/682, (‘Third Report’) para 77.
3 In 1958, the UN General Assembly invited the ILC to take up work on ‘the relations between States and intergovernmental organizations’ (UNGA Res 1289 (XIII) 5 December, 1958). The ILC first worked on the topic of ‘Representation of States in their relations with international organizations’ (1963–75) which led to the draft articles forming the basis of the Vienna Convention on the Representation of States in Their Relations with International Organizations of a Universal Character (done 14 March 1975, not yet in force) UN Doc A/CONF.67/16. The second part examined ‘Status, privileges and immunities of international organizations, their officials, experts, etc.’. In 1992, the ILC decided that the topic should not be given further consideration unless the UNGA decided otherwise.
4 These were the Vienna Convention on the Law of Treaties (23 May 1969) 1155 UNTS 331, entered into force 27 January 1980 (‘VCLT’) and subsequently the Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations (21 March 1986) 25 ILM 543 (1986), not yet in force (‘VCLT-IO’).
5 Draft Articles on Responsibility of States for Internationally Wrongful Acts, with Commentaries, Yearbook of the International Law Commission, Vol II, Pt I, Documents of the 53rd Session (2001) UN Doc A/56/10.
6 Draft Articles on the Responsibility of International Organizations with Commentaries, in Report of the International Law Commission, 63rd Session (26 April–3 June 3, 4 July 4–12 August, 2011) UN Doc A/66/10, at 52; GAOR, 66th Session, Supp No 10 (2011) (‘ARIO’).
7 Art 1.1, ILC, Guide to Practice on Reservations to Treaties, adopted by the International Law Commission at its 63rd Session, in 2011, and submitted to the General Assembly as a part of the Commission's report covering the work of that session, UN Doc A/66/10, para 75.
8 ‘Although the International Law Commission had some reservations on equating the rules applicable to international organizations to those applicable to states, it was decided in the end to assimilate international organizations to states.’ Verwey, D, The European Community, the European Union and the International Law of Treaties (TMC Asser Press 2004) 129.
9 See ILC, Fourth Report on the Provisional Application of Treaties by Juan Manuel Gómez-Robledo, Special Rapporteur, International Law Commission, 68th Session Geneva (2 May–10 June and 4 July–12 August 2016) UN Doc A/CN.4/699, para 102.
10 For example, Draft Guideline 1 sets out that ‘States and international organizations may provisionally apply a treaty, or parts thereof, when the treaty itself so provides, or when they have in some other manner so agreed, provided that the internal law of the States or the rules of the international organizations do not prohibit such provisional application.’ ILC, Third Report on the Provisional Application of Treaties by Juan Manuel Gómez-Robledo, Special Rapporteur, International Law Commission, 67th Session Geneva (4 May–5 June and 6 July–7 August 2015) UN Doc A/CN.4/687, para 131.
11 Fourth Report (n 1) para 19: ‘It was also noted that at present the reference to international organizations is not entirely consistent throughout the draft conclusions as a whole, since in places the latter refer explicitly to State practice alone.’
12 Martin, JM Cores, ‘European Exceptionalism in International Law? The European Union and the System of International Responsibility’ in Ragazzi, M (ed), The Responsibility of International Organizations: Essays in Memory of Sir Ian Brownlie (Brill 2013) 192.
13 ARIO (n 6).
14 See Kuijper, P-J and Paasivirta, E, ‘EU International Responsibility and Its Attribution: From the Inside Looking Out’ in Evans, M and Koutrakos, P (eds), The International Responsibility of the European Union: European and International Perspectives (Hart Publishing 2013) 35. Paasivirta, E and Kuijper, P-J, ‘Does One Size Fit All? The European Community and the Responsibility of International Organizations’ 36 NYIL (2005) 169, 211–12. Hoffmeister, F, ‘Litigating against the European Union and Its Member States – Who Responds under the ILC's Draft Articles on International Responsibility of International Organizations?’ (2010) 21(3) EJIL 723.
15 The ‘Regional Economic Integration Organization/Regional Integration’ (REIO/RIO) clause is discussed in more detail under the heading ‘The EU as an International Treaty Actor’ in Section IVA.
16 ‘The special situation of the European Union and other potentially similar organizations could be accommodated in the DARIO articles by special rules of attribution of conduct, so that the actions of organs of member states could be attributed to the organization, by special rules of responsibility, so that responsibility could be attributed to the organization, even if organs of member states were the prime actors of a breach of an obligation borne by the organization, or by a special exception or saving clause for organizations such as the European Community.’ Observations of Mr. Kuijper (Observer for the European Commission), Sixth Committee, Summary Record of its 21st Meeting, 18 November 2004, UN Doc A/C.6/59/SR.21, para 18.
17 Statement on behalf of the European Union, Professor G Nesi, Legal Adviser of the Permanent Mission of Italy to the United Nations. Sixth Committee, Report of the International Law Commission Chapter IV, Responsibility of International Organizations Item 152, New York, 27 October (2003) <http://eu-un.europa.eu/eu-presidency-statement-report-of-the-international-law-commission/>.
18 One of the most vocal critics was the EU itself. See Comments of the European Commission, Comments and Observations Received from International Organizations, 14 February 2011, UN Doc A.CN.4/637, 8: ‘for now the European Union remains unconvinced that the draft articles and the commentaries thereto adequately reflect the diversity of international organizations’.
19 Third Report (n 2) para 70.
20 See Crawford, J, Brownlie's Principles of Public International Law (8th edn, Oxford University Press 2013) 192.
21 Fourth Report (n 1) para 20.
22 Fourth Report (n 1) para 20.
23 The preamble of the VCLT-IO (n4) states that ‘rules of customary international law will continue to govern questions not regulated by the provisions of the present Convention’.
24 T Treves, ‘Customary International Law’ in Max Planck Encyclopedia of Public International Law at <http://opil.ouplaw.com/home/EPIL> para 51.
25 See SD Murphy, ‘The Identification of Customary International Law and Other Topics: The Sixty-Seventh Session of the International Law Commission’ GW Law School Public Law and Legal Theory Paper No 2015-38 (2015) 9–11.
26 Fourth Report (n 1) para 20.
27 ILC, Second Report on Identification of Customary International Law by Michael Wood, Special Rapporteur, International Law Commission, 66th Session, Geneva (5 May–6 June and 7 July–8 August 2014) UN Doc A/CN.4/672 (‘Second Report’) para 18.
28 Art 2(a) ARIO (n 6).
29 Art 1, para 1(1), 1975 Vienna Convention on the Representation of States in their Relations with International Organizations of a Universal Character, Doc A/CONF.67/16 (adopted and opened for signature in Vienna, 14 March 1975) not yet in force.
30 Art 2, para 1(a)(i), VCLT-IO (n4).
31 Third Report (n 2) fn 159: ‘The Special Rapporteur does not at present consider it necessary to include a definition in the draft conclusions, provided that an explanation is given in the commentary. This is a matter which the Drafting Committee may wish to consider further.’
32 ‘The definition of international organizations […] comprises entities of a quite different nature. Membership, functions, ways of deliberating and means at their disposal vary so much that with regard to responsibility it may be unreasonable to look for general rules applying for all intergovernmental organizations, especially with regard to the issue of responsibility into which States may incur for activities of the organization of which they are members. It may be necessary to devise specific rules for different categories of international organizations.’ ILC, Report of the International Law Commission on the work of its 54th Session (29 April–7 June and 22 July–16 August 2002) Official Records of the General Assembly, 54th Session, Supp No 10, UN Doc A/57/10, para 470.
33 ‘[F]or now the European Union remains unconvinced that the draft articles and the commentaries thereto adequately reflect the diversity of international organizations. Several draft articles appear either inadequate or even inapplicable to regional integration organizations such as the European Union, even when account is taken of some of the nuances now set out in the commentaries.’ ILC, Comments of the European Commission, Comments and Observations Received from International Organizations, 14 February 2011, UN Doc A.CN.4/637, 8.
34 Statement on Behalf of the European Union and Its Member States by Lucio Gussetti, Director, European Commission Legal Service at the General Assembly Sixth Committee on Item 83, ‘Identification of Customary International Law’, United Nations, New York, 4 November 2015, para 5.
35 Blokker, N and Wessel, RA, ‘Introduction: First Views at the Articles on the Responsibility of International Organizations’ (2012) 9 IOLR 1, 5.
36 See Wouters, J and Odermatt, J, ‘Are All International Organizations Created Equal?’ (2012) 9 IOLR 7–14 .
37 Fourth Report (n 1) para 20.
38 Third Report (n 2) para 71.
39 Third Report (n 2) para 72.
40 American Law Institute. Restatement of the Law, Third, the Foreign Relations Law of the United States (American Law Institute Publishers 1987) Section102 (Sources of International Law) Reporters’ Notes 2.
41 See Bordin, FL, ‘Reflections of Customary International Law: The Authority of Codification Conventions and ILC Draft Articles in International Law’ (2014) 63 ICLQ 535–67 arguing that courts and tribunals have increasingly cited ILC codification conventions and draft articles as reflections of customary international law.
42 Resolutions of the UNGA may ‘in certain circumstances, provide evidence important for establishing the existence of a rule or the emergence of an opinio juris’. Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion)  ICJ Rep 226, para 70. See also the discussion on ‘Resolutions adopted by international organizations and at international conferences’ in the Third Report (n 2) 31 and fn 114 and the authorities cited therein.
43 Draft Conclusion 12, point 2.
44 Wouters, J and De Man, P, ‘International Organizations as Law-Makers’ in Klabbers, J and Wallendahl, A (eds), Research Handbook on International Organizations Law: Between Functionalism and Constitutionalism (Edward Elgar 2011). See Third Report (n 2),fn 169 and the academic literature cited.
45 Third Report (n 2) para 75.
46 Third Report (n 2) fn 179.
47 Murphy (n 25) 7.
48 Third Report (n 2) para 77.
49 Third Report (n 2) para 77.
50 Statement on Behalf of the European Union (n 34) para 5.
51 Larik, J and Casteleiro, A Delgado, ‘The Duty to Remain Silent: Limitless Loyalty in EU External Relations’ (2011) 36 ELR 524, 540: ‘the duty of sincere cooperation in external relations manifests itself indeed rather often as a duty for the Member States to keep silent, unless told to speak by the EU institutions’. See Cremona, M, ‘Defending the Community Interest: the Duties of Cooperation and Compliance’ in Cremona, M and de Witte, B, EU Foreign Relations Law: Constitutional Fundamentals (Hart 2008).
52 Murphy (n 25) 8.
53 See eg Paasivirta, E, ‘Four Contributions of the European Union to the Law of the Sea’ in Czuczai, J and Naert, F (eds), The EU as a Global Actor – Bridging Legal Theory and Practice. Liber Amicorum in Honour of Ricardo Gosalbo Bono (forthcoming Brill 2017).
54 Third Report (n 2) para 77.
55 ILC, Identification of customary international law, Statement of the Chairman of the Drafting Committee, Mr Gilberto Saboia, 7 August 2014, Draft Conclusion 4 , para 2: ‘In certain cases, the practice of international organizations also contributes to the formation, or expression, of rules of customary international law.’
56 Third Report (n 2) para 79.
57 Statement on Behalf of the European Union (n 34) para 11.
58 Third Report (n 2) paras 68–79.
59 Fourth Report (n 1) Annex, Draft conclusion 4.
60 Treaty on European Union (as amended by the Treaty of Lisbon) (13 December 2007) Official Journal C 326 (26 October 2012), entered into force 1 December 2009.
61 The Court has interpreted this to mean that ‘when [the Union] adopts an act, it is bound to observe international law in its entirety, including customary international law, which is binding upon the institutions of the European Union.’ Judgment in Air Transport Association of America and Others v Secretary of State for Energy and Climate Change, C-366/10, EU:C:2011:864, para 101. See Kuijper, P-J, ‘‘‘It Shall Contribute to … the Strict Observance and Development of International Law…’’ The Role of the Court of Justice’ in Rosas, A, Levits, E and Bot, Y (eds), The Court of Justice and the Construction of Europe: Analyses and Perspectives on Sixty Years of Case-law (TMC Asser Press 2013).
62 An example of such a work is Hoffmeister, F, ‘The Contribution of EU Practice under International Law’ in Cremona, M (ed), Developments in EU External Relations Law (Oxford University Press 2008). Regarding the Law of the Sea, see Paasivirta (n 53); Boelaert-Suominen, S, ‘The European Community, the European Court of Justice and the Law of the Sea’ (2008) 23 The International Journal of Marine and Coastal Law 643.
63 Regarding the adaptation of the law of treaties to the context of the EU, see Verwey, D., The European Community, the European Union and the International Law of Treaties (The Hague, TMC Asser Press, 2004); Odermatt, J, ‘The Use of International Treaty Law by the Court of Justice of the European Union’ (2015) 7 Cambridge Yearbook of European Legal Studies 121.
64 See Statement on behalf of the European Union by Eglantine Cujo, Legal Adviser, Delegation of the European Union to the United Nations, at the Sixth Committee on Agenda item 78 on Identification of customary international law.
65 ARIO (n 6).
66 Commentary to art 9 ARIO (n 6) (Conduct acknowledged and adopted by an international organization as its own).
67 Third report on the provisional application of treaties (n 10) para 123.
68 Fourth report on the provisional application of treaties (n 9) paras 156–161, providing examples of the provisional application of treaties by the EU.
69 Vanhamme, J, ‘Formation and Enforcement of Customary International Law: The European Union's Contribution’ (2008) 29 NYIL 131.
70 See European Union, Treaties Office Database. Available at <http://ec.europa.eu/world/agreements/default.home.do>. Statistics as of 11 January 2017. This includes an inventory of all agreements to which the European Union (EU), the European Community (EC), the European Economic Community (EEC), or the European Atomic Energy Community (EURATOM) is a party.
71 Council Decision 2010/48/EC of 26 November 2009 concerning the conclusion, by the European Community, of the United Nations Convention on the Rights of Persons with Disabilities  OJ L23/35.
72 European Commission, ‘EU ratifies UN Convention on disability rights’, Press Release, 5 January 2011, <http://europa.eu/rapid/press-release_IP-11-4_en.htm>.
73 These plans have been derailed by Opinion 2/13 in which the Court held that the Draft Accession agreement designed to allow the EU become as an ECHR contracting party was not consistent with the EU Treaties. Opinion 2/13 of 18 December 2014, Accession of the EU to the ECHR, EU:C:2014:2454.
74 Racke v Hauptzollamt Mainz, C-162/96, EU:C:1998:293.
75 Brita v Hauptzollamt Hamburg Hafen, C-386/08, EU:C:2010:91, para 40.
76 Art 44 of the Convention on the Rights of Persons with Disabilities (CRPD), New York, 13 December 2006, entry into force 28 May 2008, UNTS 2514, 3 allows participation by regional integration organizations. It defines a RIO as ‘an organization constituted by sovereign States of a given region, to which its member States have transferred competence in respect of matters governed by this Convention.’
77 Art 305(1)(f), United Nations Convention on the Law of the Sea (‘UNCLOS’), signed at Montego Bay, 10 December 1982, entry into force 16 November 1994, UNTS 1833, 3: ‘This Convention shall be open for signature by international organizations, in accordance with Annex IX.’
78 Art 1, para 5. Fifth Negotiation Meeting Between the CDDH ad hoc Negotiation Group and the European Commission on the Accession of the European Union to the European Convention on Human Rights, ‘Final report to the CDDH’, 47+1(2013)008rev2, Strasbourg, 10 June 2013, Appendix I ‘Draft revised agreement on the accession of the European Union to the Convention for the Protection of Human Rights and Fundamental Freedoms’.
79 eg art II(5), Constitution of the Food and Agricultural Organization (with Annexes) (adopted 16 October 1945, entered into force 16 October 1945) 145 BSP 910.
80 See J Heliskoski, ‘EU Declarations of Competence and International Responsibility’ in Evans and Koutrakos (n 14) 189.
81 Draft Declaration of competences by the European Union in respect of matters covered by the Constitution of the Food and Agriculture Organization of the United Nations (FAO), in Communication from the Commission to the Council, The role of the European Union in the FAO after the Treaty of Lisbon: Updated Declaration of Competences and new arrangements between the Council and the Commission for the exercise of membership rights of the EU and its Member States, COM(2013) 333 fin, annex 2, 13.
82 See P-J Kuijper and E Paasivirta, ‘EU International Responsibility and Its Attribution: From the Inside Looking Out’ in Evans and Koutrakos (n 14) 70.
83 Statement on Behalf of the European Union (n 34) para 8.
84 See, for instance, the Oxford Reports on International Law in EU Courts <http://opil.ouplaw.com/page/ILEC/oxford-reports-on-international-law-in-eu-courts> which compiles and analyses key judgments of EU courts dealing with questions of international law.
85 Third Report (n 2) para 58.
86 As Rosas argues, ‘it should be recalled that the ECJ, or the other EU courts, including the national courts of the Member States, are not international courts primarily called upon the deliver authoritative interpretations of public international norms’. A Rosas, ‘International Responsibility of the EU and the ECJ’ in Evans and Koutrakos (n 14) 159.
87 Arguing that the CJEU plays a dual role, see Odermatt, J, ‘The Court of Justice of the European Union: International or Domestic Court?’ 3 CJICL (2014).
88 Crawford (n 20) 194.
89 Aust, HP, Rodiles, A and Staubach, P, ‘Unity or Uniformity? Domestic Courts and Treaty Interpretation’ 27 LJIL 1 (2014) 75, 100 arguing, ‘[i]t has become more and more common, however, to regard the ECJ as being functionally equivalent to a municipal court’.
90 Rather, art 52 TEU sets out that the EU Treaties shall apply to the EU Member States.
91 Judgment in Ahlström Osakeyhtiö and Others v Commission (‘Woodpulp’), Joined Cases 89/85, 104/85, 114/85, 116/85, 117/85 and 125/85 to 129/85, EU:C:1993:120, paras 14–18.
92 ibid para 18.
93 Judgment in Imperial Chemical Industries Ltd. v Commission of the European Communities, Case 48–69 EU:C:1972:70.
94 Directive 2003/87/EC of the European Parliament and of the Council of 13 October 2003 establishing a scheme for greenhouse gas emission allowance trading within the Community and amending Council Directive 96/61/EC, 25 OJ 2003 L 275, a7 32 (25 October 2002).
95 Woodpulp (n 92).
96 Judgment in Commune de Mesquer, C-188/07, EU:C:2008:359.
97 Air Transport Association of America (n 61) paras 125–130. See De Baere, G and Ryngaert, C, ‘The ECJ's Judgment in Air Transport Association of America and the International Legal Context of the EU's Climate Change Policy’ (2013) 18 European Foreign Affairs Review 389, 400.
98 Judgment in Parliament v Council and Commission v Council, Joined Cases C-103/12 and C-165/12, EU:C:2014:2400.
99 D Verwey (n 8) 93. Nuclear Tests Case (New Zealand v France)  ICJ Rep 457, para 46.
100 See Odermatt, J, ‘The Use of International Treaty Law by the European Court of Justice’ 17 Cambridge Yearbook of European Legal Studies (2015) 121.
101 As Brölmann points out, ‘[o]rganisations are involved in almost all fields of human cooperation, where they present themselves not only as institutional fora for states, but also as independent international actors’. Brölmann, C, The Institutional Veil in Public International Law: International Organisations and the Law of Treaties, (Hart 2007) 1.
102 Murphy (n 25).
* Jed Odermatt, Postdoctoral Research Fellow, University of Copenhagen, Centre of Excellence for International Courts (iCourts), Jed.Odermatt@jur.ku.dk. This contribution is based on a paper presented at the 2016 European Society of International Law Research Forum at Koç University Law School and the Center for Global Public Law in Istanbul. I would like to thank the organisers of the conference and the panel participants for their comments and feedback. I would also like to thank those who have commented on earlier drafts, including Marise Cremona, Esa Paasivirta, Thomas Ramopoulos, Miriam Cullen and Graham Butler.
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