Marking the 50th anniversary of the influential ERTA doctrine, this book analyses and contextualises the entire breadth of the jurisprudence of EU external relations law through a systematic, case-by-case account of the field. The entire framework of EU external relations law has been built from the ground up by the jurisprudence of the Court of Justice of the European Union. At the beginning of the field's emergence, the legal questions to be answered concerned the division of powers and competence between, firstly, the Member States and that of the Union; and secondly, the division of powers and competence between the different institutions of the Union. Questions on such matters continue to be asked, but more contemporarily, new legal questions have arisen that have been in need of adjudication, including questions concerning the autonomy of Union law; the relationship between the Union and other international organisations; the relationship between Union law and international law; the scope and breadth of international agreements; amongst others. The book features established academic scholars, judges, agents of institutions and Member States, and legal practitioners in the field of EU external relations law, analysing over 90 cases in which the Court has legally shaped the theory and practice of the external dimension of legal Europe. Cited in Opinion of Advocate General Nicholas Emiliou in Case C-516/22, European Commission v United Kingdom of Great Britain and Northern Ireland, ECLI:EU:C:2023:857 (Judgment of the UK Supreme Court), Court of Justice of the European Union, 9 November 2023; and, Opinion of Advocate General Nicholas Emiliou in Case C 728/23 P, Kingdom of Spain v Robert Stockdale, Council of the European Union, European Commission, European External Action Service (EEAS), European Union Special Representative in Bosnia and Herzegovina, ECLI:EU:C:2025:710, Court of Justice of the European Union, 18 September 2025.

Table of Contents:
EU External Relations Law and Navigating the Case Law of the Court of Justice of the European Union Graham Butler and Ramses A Wessel 1. Implied Powers of the EU, Limits to Political Expediency and Internationally Inspired Pragmatism: Commission v Council (ERTA) Inge Govaere 2. International Agreements in the EU Legal Order: International Fruit Alessandro Petti and Joanne Scott 3. International Agreements as an Integral Part of EU Law: Haegeman Ramses A Wessel 4. Common Commercial Policy and the Determination of Exclusivity: Opinion 1/75 (Local Cost Standard) Marise Cremona and Jaka Kukavica 5. The EU Customs Union, International Agreements of EU Member States and the Doctrine of Substitution: Nederlandse Spoorwegen Graham Butler 6. Establishing Direct Effect of Provisions in International Agreements: Bresciani Timothy Roes 7. Refining and Expanding Implied Powers of the Union: Kramer Tobias Lock 8. Linking Internal and External Trade in a Perfect Customs Union: Donckerwolcke Piet Eeckhout 9. EU External Competence in the Absence of Internal Rules, and the Sleeping Beauty: Opinion 1/76 (Laying Up Fund for Inland Waterway Vessels) Allan Rosas 10. The Birth of the Principle of Close Cooperation, Declaration of Competences, and the Ruling Procedure: Ruling 1/78 (Convention on Nuclear Protection) Anna Södersten 11. Defining the Scope of the Treaty-Making Competence for the Formulation of the Common Commercial Policy: Opinion 1/78 (Natural Rubber) Per Cramér 12. International Agreements Concluded by Member States Prior to their EU Accession: Burgoa Panos Koutrakos 13. The Purpose of International Agreements and their Direct Effect: Polydor Jan Klabbers 14. Status and Enforceability of EU International Agreements within the Domestic Legal Systems of the Member States: Kupferberg Eleftheria Neframi 15. The EU's Common Customs Tariff, Uniform Application of International Agreements, and the Demarcation between EU and Member State 'Spheres of International Law': SPI/SAMI Dylan Geraets 16. Direct Effect of Association Agreements and the Meaning of 'Association': Demirel Guillaume Van der Loo 17. Judicial Review of EU Measures in the Light of WTO Rules: Fediol and Nakajima Tamara Perišin and Ilektra Antonaki 18. The Integration of Decisions of Association Councils in EU Law: Greece v Commission (Special Aid to Turkey) Fernando Castillo de la Torre 19. The Legal Effects of Decisions of Autonomous Bodies Established under an International Agreement: Sevince Nathan Cambien 20. The Union's Participation in Legally Binding International Third-Party Dispute Settlement: Opinion 1/91 (EEA I) and Opinion 1/92 (EEA II) Esa Paasivirta 21. Setting the Multiple Functions of Customary International Law in the EU Legal Order: Poulsen Charlotte Beaucillon 22. ERTA, Mixity and the Duty of Cooperation in the Conclusion of International Agreements: Opinion 2/91 (ILO Convention) Mirka Kuisma 23. The Reviewability of Acts Adopted by the Member States Meeting within the Council: Parliament v Council and Commission (Bangladesh Aid) Luca Pantaleo 24. Legality of the European Development Fund and the European Parliament's Prerogatives: Parliament v Council (European Development Fund) Sandra Bartelt 25. Unrecognised 'States' and EU Law: Anastasiou I Alina Tryfonidou 26. No General Treaty-Making Power of the Commission to Conclude International Administrative Agreements: France v Commission I Andrea Ott 27. Consistent Interpretation and Continuous Dialogue between the EU and the WTO: Germany v Council (Bananas) Joseph A McMahon 28. A Setback in a Never-Ending Expansion to External Competence? Opinion 1/94 (WTO) Enzo Cannizzaro 29. The Scope of the Union's Exclusive External Competences and the Verification of Competence: Opinion 2/92 (OECD) Daniel Sarmiento 30. Unilateral Measures of Member States Affecting the Internal Market and the Law/Politics Divide in External Relations: Commission v Greece (FYROM) Henri de Waele 31. EU Membership in International Organisations and the Joint Exercise of Membership Rights: Commission v Council (FAO) Rita Guerreiro Teixeira and Jan Wouters 32. The First Attempt at EU Accession to the ECHR: Opinion 2/94 Stian Oby Johansen 33. Enforcement of International Sanctions within the EU Legal Order: Bosphorus Aindrias Ó Caoimh 34. Scope of EU Development Policy: Portugal v Council (India Cooperation Agreement) Morten Broberg 35. Legal Certainty and Customary International Law: Opel Austria Marcus Klamert 36. Invoking Customary International Law before the Court: Racke Jed Odermatt 37. The Effect of WTO Law in the EU Legal Order: Portugal v Council Holger P Hestermeyer 38. The Member States' Duty to Denounce Anterior Treaties: Commission v Portugal (Maritime Policies) Hannes Lenk 39. The Relationship between the Common Commercial Policy and Other External Competences of the EU: Opinion 2/00 (Cartagena Protocol) Koen Lenaerts and Stanislas Adam 40. Autonomy of the EU Legal Order and International Agreements Extending the Acquis: Opinion 1/00 (European Common Aviation Area) Cécile Rapoport 41. Clarification of Exclusive Implied External Competence of the Union: Open Skies Wybe Th Douma 42. Respect for Institutional Balance in the Adoption of Non-legally Binding Agreements: France v Commission II Paula García Andrade 43. The Effect of WTO Dispute Settlement Body Decisions in EU Law: Van Parys Karsten Engsig Sorensen 44. Direct Effect of the EU–Russia Partnership and Cooperation Agreement, Non-discrimination and the Beautiful Game: Simutenkov Adam Lazowski 45. The Indissociable Link between Environmental Policy and the Common Commercial Policy: Commission v Council (Rotterdam Convention I) Geert De Baere 46. Lowering the Threshold for Finding Implied Powers: Opinion 1/03 (Lugano Convention) Merijn Chamon 47. The Exclusive Jurisdiction of the Court and International Courts: Commission v Ireland (Mox Plant) Andrés Delgado Casteleiro 48. Judicial Protection in Autonomous Restrictive Measures Involving Composite Administrative Procedures: OMPI Trevor Redmond 49. The Autonomy of EU Law vis-a-vis International Law: Kadi I and Kadi II Christina Eckes 50. Laying the Foundation for a Broad Scope of EU Development Cooperation Policy and its Delimitation with Other EU External Competence: Parliament v Commission (Philippines Border Management) Tina Van den Sanden 51. The Pre-Lisbon Machinery for the Delimitation of the CFSP: Commission v Council (ECOWAS) Rass Holdgaard and Gustav Krohn Schaldemose 52. The Legal Effects of the MARPOL Convention and the UN Convention on the Law of the Sea: Intertanko Mario Mendez 53. Implied External Exclusivity and the Duty of Loyal Cooperation in International Organisations: Commission v Greece (International Maritime Organisation) Thomas Ramopoulos 54. Visa Requirements for Turkish Citizens: Soysal & Savatli and Demirkan Bruno De Witte 55. The Application of EU Law in an Unrecognised Entity: Apostolides v Orams Nikos Skoutaris 56. Potential Incompatibility of International Agreements Concluded by Member States before Accession: Commission v Austria, Commission v Sweden and Commission v Finland Luigi Lonardo 57. The Application of EU International Agreements to Occupied and Disputed Territories: Brita Paul James Cardwell 58. Union Loyalty in Mixed External Relations and the Weight of Informal Preparatory Acts: Commission v Sweden (PFOS) Pieter Jan Kuijper 59. The Ambivalent Clarifi cation of the Effects of International Conventional and Customary Law in the European Union: Air Transport Association of America Isabelle Bosse-Platiere 60. The Choice of Legal Basis between the AFSJ and the CFSP: Parliament v Council (Smart Sanctions) José Manuel Cortés Martín and Gloria Fernández Arribas 61. Common Commercial Policy or Internal Market Rules as the Legal Basis for the Conclusion of International Agreements after Lisbon: Commission v Council (Conditional Access Convention) Roberto Mastroianni and Giorgia Lo Tauro 62. The Choice of Legal Basis for Coordination of Social Security Systems with Associated Third Countries: UK v Council (EEC–Turkey) Katarina Hyltén-Cavallius 63. Jurisdiction of the EU Courts in the CFSP when Linked to the EU Budget: Elitaliana Ricardo da Silva Passos 64. Intellectual Property and the Post-Lisbon Common Commercial Policy: Daiichi Sankyo Joris Larik 65. The Application of EU Internal Competences in an External Context: UK v Council (EEA) Tarjei Bekkedal 66. The Normalisation of CFSP International Agreements in the EU Legal Order: Parliament v Council (Mauritius) and Parliament v Council (Tanzania) Juan Santos Vara 67. The Legal Basis for International Agreements in the fi eld of Development Cooperation Post-Lisbon, and its Potential as a Catch-All Provision: Commission v Council (Philippines PCA) Stephan Marquardt and Soledad Rodríguez Sánchez-Tabernero 68. Member States as Trustees of the Union in International Organisations: Germany v Council (OIV) Theodore Konstadinides 69. The ERTA Doctrine Post-Lisbon: Opinion 1/13 (Convention on the Civil Aspects of International Child Abduction) Christian Thorning 70. The Second Attempt at EU Accession to the ECHR: Opinion 2/13 Katja S Ziegler 71. The Impact of Obligations under International Agreements on the (Judicial) Review of EU Measures: Stichting Natuur en Milieu and Pesticide Action Network Europe Anne Thies 72. Hybrid Acts of the EU and its Member States Concerning International Agreements: Commission v Council (US Air Transport Agreement) Joni Heliskoski 73. Balancing Institutional Powers in Negotiating Directives and EU External Environmental Relations: Commission v Council (Australia ETS) Sanja Bogojevic 74. EU Representation in International Litigation: Council v Commission (International Tribunal for the Law of the Sea) Alexander Kornezov 75. The Compatibility of EU International Agreements Extending to Occupied Territories with International Law: Front Polisario and Western Sahara Campaign UK Eva Kassoti 76. The Scope of the Court's Jurisdiction in the CFSP: H v Council and Others Luca Prete 77. Institutional Balance in the Conclusion of Non-binding International Agreements Revisited: Council v Commission (Swiss MoU) Anders Neergaard 78. The Concept of (Non-)Commerciality and the ERTA Doctrine Post-Lisbon: Opinion 3/15 (Marrakesh Treaty) Gesa Kübek 79. Attribution of Authorship of 'EU' Legal Acts: NF and Others v European Council Mauro Gatti 80. The Absence of Rights to Humanitarian Visas, and Missions of EU Member States in Third Countries: X and X v Belgium Louise Halleskov 81. Securing a Coherent System of Judicial Protection in Relation to Restrictive Measures: Rosneft Peter Van Elsuwege 82. The EU Competence to Conclude the New Generation of Free Trade Agreements: Opinion 2/15 (EU–Singapore FTA) Christine Kaddous 83. International Agreements Assessed Through the Prism of the Charter of Fundamental Rights: Opinion 1/15 (EU–Canada PNR) Suzanne Kingston 84. The Unitary Representation of the Union in an International Forum and Clarification of Shared Competence and Facultative Mixity Post-Lisbon: Germany v Council (COTIF I) and Commission v Germany (COTIF II) Maciej Szpunar and Roland Klages 85. The Web of Autonomy of the EU Legal Order: Achmea Xavier Groussot and Marja-Liisa Öberg 86. The Delineation between CFSP and Non-CFSP Matters: Commission v Council (Kazakhstan) Thomas Verellen 87. Mixity and Exercising Shared Competence in International Fora: Commission v Council (Antarctic Marine Protected Areas) Frederik Naert 88. Investor–State Dispute Tribunals Established under EU International Agreements: Opinion 1/17 (EU–Canada CETA) Kieran Bradley 89. Ensuring Respect for International Humanitarian Law Through Labelling Requirements: OJE and Vignoble Psagot Sara Poli 90. Inter se Agreements between Member States, and the Outer Limits of the Court's Jurisdiction in Infringement Proceedings: Slovenia v Croatia Federico Casolari 91. Jurisdiction of the Court for Non-contractual Liability and Actions for Damages Claims within the CFSP: Bank Refah Kargaran Graham Butler and Ramses A Wessel 92. The Right of Third States to Challenge EU Restrictive Measures before the Court: Venezuela v Council Francesca Finelli