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Disciplining Member States: EU Loyalty in External Relations

Published online by Cambridge University Press:  12 March 2020

Christina ECKES*
University of Amsterdam


This Article argues that the cooperation obligations of the Member States under EU law are best understood as forming part of an overall duty of EU loyalty and elaborates on the consequences of framing it in this way. EU loyalty legally requires Member States to make the common EU interest their own. The Article further demonstrates that EU loyalty is more relevant and more stringently applied in EU external relations than within the EU legal order. Loyalty obligations of the Member States reach into the future, extend to hypothetical situations, and are at a comparatively high level of abstraction aimed to protect the Union's ability to act effectively on the international plane. This limits Member States’ margin of manoeuvre, including when they take unilateral external action within the realm of their retained national competences. The Article explains that this may be functionally justified by the high stakes of non-concerted external action. However, and in particular with the EU's increased external powers and the ever-growing relevance of international cooperation, the stringent application of cooperation requirements should be (better) explicated and justified.

Copyright © The Author(s), 2020. Published by Cambridge University Press on behalf of Centre for European Legal Studies, Faculty of Law, University of Cambridge

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Professor of European Law, University of Amsterdam and Director, Amsterdam Centre for European Law and Governance, This Article draws from Chapter 2 of C Eckes, EU Powers under External Pressure (Oxford University Press, 2019).


1 Commission v Germany, C-620/16, EU:C:2019:256, para 93; Commission v Sweden, C-246/07, EU:C:2010:203, para 73 (with more references).

2 Judicial challenges concerning power relations in the area of external relations since the entry into force of the Lisbon Treaty: Parliament v Council (UN Sanctions), C-130/10, EU:C:2012:472; Commission v Council, C-28/12, EU:C:2015:282; Dai-Ichi Sankyo, C-414/11, EU:C:2013:520; Commission v Council, C-114/12, EU:C:2014:2151; Commission v Council (Services Convention), C-137/12, EU:C:2013:675; Commission v Council, C-377/12, EU:C:2014:1903; Council v Commission, C-660/13, EU:C:2016:616; European Parliament v Council, C-263/14, EU:C:2016:435; Commission v Council (Emission Trading System), C-425/13, EU:C:2015:483; Commission v Council (Lisbon Agreement on Appellations of Origin and Geographical Indications), C-389/15, EU:C:2017:798; Commission v Council (CMR-15), C-687/15, EU:C:2017:803; Commission v Council (Antarctica), Joined Cases C-626/15 and C-659/16, EU:C:2018:925; Commission v Council (PCA with Kazakhstan), C-244/17, EU:C:2018:662. See also Cardwell, P, ‘The Legalisation of European Union Foreign Policy and the Use of Sanctions’ (2015) 17 Cambridge Yearbook of European Legal Studies 287CrossRefGoogle Scholar.

3 Royce, J, The Philosophy of Loyalty (Macmillan, 1908), pp 1617Google Scholar.

4 Ibid, pp 14–15.

5 Hooghe, L and Marks, G, ‘Grand Theories of European Integration in the Twenty-First Century’ (2019) 26(8) Journal of European Public Policy 1113CrossRefGoogle Scholar.

6 Haas, E B, The Uniting of Europe: Political, Social and Economic Forces 1950–1957 (Stanford University Press, 1958), p 16Google Scholar.

7 Millward, A S The European Rescue of the Nation State (Routledge, 1992)Google Scholar.

8 See typology by Pollack, M, ‘Realist, Intergovernmentalist, and Institutionalist Approaches’ in Jones, E, Menon, A, and Weatherill, S (eds), The Oxford Handbook of the European Union (Oxford University Press 2012)Google Scholar.

9 Article 53 TEU.

10 In the landmark case of Costa v ENEL, C-6/64, EU:C:1964:66, the CJEU referred to sincere cooperation as one of a number of principles justifying primacy. In Confédération paysanne, C-298/12, EU:C:2013:630, para 37, the Court exclusively bases primacy on ‘cooperation in good faith’.

11 For notification duties of the executive, see eg Kortas, C-319/97 EU:C:1999:272.

12 Inter-Environnement Wallonie, Case C-129/96, EU:C:1997:628, para 45 (the case concerned an order from the Walloon Council).

13 Zwartveld, C-2/88, EU:C:1990:440, para 18; Marleasing, C-106/89, EU:C:1990:395, para 8; Peterbroeck, C-312/93, EU:C:1995:437; Dior, Joined Cases C-300-392/98, EU:C:2000:688; Kühne & Heitz, C-453/00, EU:C:2004:17, paras 24–27; Laboratoires Boiron, C-526/04, EU:C:2006:528, paras 55, 57; VTB-VAB and Galatea, Joined Cases C-261-299/07, EU:C:2009:244, para 39; Marra, Joined Cases C-200-201/07, EU:C:2008:579, para 41; Stergios Delimitis, C-234/89, EU:C:1991:91 (Commission vis-à-vis national judiciary); Commission v Austria, C-205/06, EU:C:2009:118, para 44 (Commission must facilitate cooperation between Member States); Confédération paysanne, note 10 above, para 37; Pupino, C-105/03, EU:C:2005:386, para 42–43 (principle of loyal cooperation applicable in the former third pillar and in particular on the national courts). See also Cremona, M, ‘Defending the Community Interest: The Duties of Cooperation and Compliance’ in Cremona, M and de Witte, B (eds), EU Foreign Relations Law: Constitutional Fundamentals (Hart Publishing, 2008), p 158Google Scholar.

14 Lesoochranárske zoskupenie VLK (Slovak Bear II), C-243/15, EU:C:2016:838, para 50. See on the ambiguous use of effectiveness and effective judicial protection in the case law, Bergström, J, ‘The Principle of Effective Judicial Protection after the Lisbon Treaty’ (2011) 4 Review of European Administrative Law 53Google Scholar.

15 Peterbroeck, note 13 above.

16 Rewe-Zentralfinanz, C-33/76, EU:C:1976:188, para 5 (‘impossible in practice’); Surgicare, C-662/13, EU:C:2015:89 (‘impossible in practice or excessively difficult’).

17 Costanzo, C-103/88, EU:C:1989:256. See also Lucchini, C-119/05, EU:C:2007:434, in which the Court, drawing on loyal cooperation, held that the duty of the Member States, eg national governments, to recover illegal state aid could justify ignoring the principle of res judicata. This could be read as an erosion of the power of national courts over the other branches of government.

18 The Court uses loyal and sincere cooperation interchangeably. This is also what this Article does.

19 Commission v Belgium, C-47/08, EU:C:2011:334, para 141 et seq.

20 Klamert, M, The Principle of Loyalty in EU Law (Oxford University Press 2014), pp 32, 55 et seqCrossRefGoogle Scholar.

21 Tushnet, M, ‘What Then Is the American?’ (1996) 38 Arizona Law Review 873, 879–81Google Scholar, emphasising the adversarial nature of interaction between the federate and federal level within the United States.

22 Commission v Council, C-22/70, EU:C:1971:32.

23 Ibid, paras 20–22.

24 Klamert, note 20 above, p 75.

25 Bilateral Investment Treaty cases (Commission v Austria, note 13 above, paras 1–3, 16–45; Commission v Sweden, C-249/06, EU:C:2009:119; Commission v Finland, C-118/07, EU:C:2009:715; see also eg Commission v Belgium, C-170/98, EU:C:1999:411; Commission v Portugal, C-84/98, EU:C:2000:359; Commission v Portugal, C-62/98, EU:C:2000:358. See for more details, Kokott, J and Sobotta, C, ‘Investment Arbitration and EU Law’ (2016) 18 Cambridge Yearbook of European Legal Studies 3CrossRefGoogle Scholar.

26 Commission v Finland, C-118/07, EU:C:2009:525, Opinion of AG Maduro, paras 23 et seq.

27 See Denza, E, ‘Bilateral Investment Treaties and EU Rules on Free Transfer: Comment on Commission v Austria, Commission v Sweden and Commission v Finland’ (2010) 35(2) European Law Review 263, 269Google Scholar et seq.; Lavranos, N, ‘New Developments in the Interaction between International Investment Law and EU Law9(3) (2010) The Law and Practice of International Courts and Tribunals 409, 421 et seqCrossRefGoogle Scholar.

28 Opinion 1/13, EU:C:2014:2303.

29 Ibid, para 72.

30 Ibid, para 89.

31 Commission v Finland, note 26 above, Opinion of AG Maduro, paras 23 et seq.

32 Inter-Environnement Wallonie, note 12 above.

33 Commission v Greece, C-45/07, EU:C:2009:81 (hereinafter ‘IMO case’).

34 Ibid, paras 24–26.

35 Portuguese Republic v Council of the European Union, C-149/96, EU:C:1999:574, paras 34–46. See also International Fruit Company NV and others v Produktschap voor Groenten en Fruit, C-21/72, EU:C:1972:115, para 21.

36 Opinion 1/17, EU:C:2019:72, Opinion of AG Bot, para 72 et seq.

37 OIV, C-399/12, EU:2014:2258 (hereinafter ‘OIV case). Examples of critical voices are, Govaere, I, ‘Novel Issues Pertaining to EU Member States Membership of Other International Organisations: The OIV Case’ in Govaere, I, Lannon, E, Elsuwege, P, and Adam, S (eds) The European Union in the World (Brill Nijhoff 2014)CrossRefGoogle Scholar; Konstadinides, T, ‘In the Union of Wine: Loose Ends in the Relationship between the European Union and the Member States in the Field of External Representation: Case C-399/12 Germany v. Council, Judgment of the Court of Justice of 7 October 2014, nyr’ (2015) 21(4) European Public Law 679Google Scholar.

38 OIV case, note 37 above.

39 Commission v Sweden (PFOS), C-246/07 EU:C:2010:203 (hereinafter PFOS, C-246/07).

40 See Casteleiro, A Delgado and Larik, J, ‘The Duty to Remain Silent: Limitless Loyalty in EU External Relations?’ (2011) 36 European Law Review 522, 534 et seq.Google Scholar; Casolari, FThe Principle of Loyal Co-operation: A “Master Key” for EU External Representation?’ in Blockmans, S and Wessel, R (eds), Principles and Practices of EU External Representation (CLEER Working Papers 2012/5), p 20Google Scholar.

41 Green Network SpA, C-66/13, EU:C:2014:156, Opinion of AG Bot, para 103.

42 Opinion 2/13, EU:C:2014:2454; Opinion 2/91, EU:C:1993:106, para 36; see also PFOS, EU:C:2009:589, Opinion AG Maduro, para 37.

43 Opinion 2/91, note 42 above, para 36.

44 M Cremona, ‘External Relations of the EU and the Member States: Competences, Mixed Agreements, International Responsibility, and Effects of International Law’ (EUI, 2006) Working Paper 22/2006, p 5 (on the position of Denmark in the context of the Lugano II Convention).

45 OIV case, note 37 above.

46 PFOS, C-246/07, note 39 above, para 103.

47 Ibid, paras 98–99.

48 Ibid, para 101.

49 Ibid, para 102.

50 PFOS, Opinion AG Maduro, note 42 above, para 56.

51 Commission v Germany, C-620/16, EU:C:2019:256.

52 Ibid, paras 45–47.

53 Ibid, para 98.

54 Article 21 TEU.

55 PFOS, note 39 above.

56 Hermès International, C-53/96, EU:C:1997:539, Opinion of AG Tesauro, para 21. See also Kuijper, PJ, ‘International Responsibility for EU Mixed Agreements’ in Hillion, C and Koutrakos, P (eds), Mixed Agreement Revisited – The EU and its Member States and the World (Hart Publishing, 2010)Google Scholar.

57 Italy v Council (premium for potato starch), C-166/78, EU:C:1979:195, para 6. Reaffirmed in Commission v Parliament and Council (Comitology), C-378/00, EU:C:2003:42, para 28; Parliament v Council (Schengen Borders Code), C-355/10, EU:C:2012:516, paras 37–40.

58 The difficulty of agreeing multilateral treaties is illustrated by the Arms Trade Treaty which was registered in December 2014,, for which the General Assembly started seeking views of the UN Member States on a legally binding instrument establishing common international standards for the import, export, and transfer of conventional arms in 2008. See GA Resolution 61/89 and the UN Convention on Contracts for the International Sale of Goods (CISG) 1980, which arose from the conclusions of a working group which was established in 1969.

59 For example, recommendations and opinions of several international bodies feature prominently in the discourse around Ireland's recent repeal of its abortion ban. Eg the UN Human Rights Committee (‘UNHRC’) in Mellet v Ireland, Human Rights Committee, Communication No. 2324/2013, UN Doc. CCPR/C/116/D/2324/2013 (2016) and Whelan v Ireland, Communication No. 2425/2014 CCPR/C/119/D/2425/2014 (2017); and the ECtHR in A, B and C v Ireland (2011) 53 EHRR 13, but also the World Health Organization (‘WHO’) guidelines (see WHO (2012) Safe Abortion: Technical and Policy Guidance for Health Systems,

60 Brölmann, C, ‘A Flat Earth? International Organizations in the System of International Law’ (2001) 70 Nordic Journal of International Law 319CrossRefGoogle Scholar.

61 Eg when the EU sought to become an observer in the UN General Assembly in 2010 and other states in the General Assembly voted against this. See L Phillips, ‘EU Wins New Powers at Global Body, Transforming Global Body’, EU Observer, 3 May 2011,

62 See eg Franck, Thomas, Political Questions Judicial Answers – Does the Rule of Law Apply to Foreign Affairs? (Princeton University Press, 1992)Google Scholar; Kuijper, PJ et al. , The Law of EU External Relations, 2nd ed (Oxford University Press, 2015), p 655Google Scholar. For recent developments in this area, see also Poli, S, ‘The Common Foreign Security Policy after Rosneft: Still Imperfect but Gradually Subject to the Rule of Law’ (2017) 54 Common Market Law Review 1799Google Scholar.

63 See the CJEU's case law denying direct effect of WTO law.

64 Article 207 TFEU.

65 See case law in note 2 above.

66 Lenaerts, K, ‘EU Federalism in 3-D’ in Cloots, E, de Baere, G, and Scottiaux, S (eds), Federalism in the European Union (Hart Publishing, 2012)Google Scholar.

67 Cf comprehensively already Cullen, H and Charlesworth, A, ‘Diplomacy by Other Means: The Use of Legal Basis Litigation as a Political Strategy by the European Parliament and Member States’ (1999) 36(6) Common Market Law Review 1243CrossRefGoogle Scholar.

68 OIV case, note 37 above; Germany v Council, C-600/14, EU:C:2017:935; United Kingdom v Council, C -656/11, EU:C:2014:97.

69 Eg Opinion 1/13, note 28 above; EU Singapore Free Trade Agreement, Opinion 2/15, EU:C:2017:376; pending Opinion 1/17, AG Bot's Opinion, note 36 above.

70 Commission v Council, note 2 above: twelve intervening Member States. Commission v Council, note 2 above: five intervening Member States; Tanzania Pirates Agreement, note 2 above: three intervening Member States; Commission v Council, note 2 above: eight intervening Member States; Commission v Council, note 2 above: twelve intervening Member States; Commission v Council, note 2 above: four intervening Member States; OIV case, note 37 above: seven intervening Member States.

71 Commission v Council (Antarctica), note 2 above, para 75.

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