Butler, G 2019, Constitutional Law of the EU’s Common Foreign and Security Policy: Competence and Institutions in External Relations. Modern Studies in European Law series, Hart Publishing (imprint of Bloomsbury Publishing), Oxford.

The Common Foreign and Security Policy (CFSP) of the European Union is a highly exceptional component of the EU legal order. This constitutionalised foreign policy regime, with legal, diplomatic, and political DNA woven throughout its fabric, is a distinct sub-system of law on the outer-most sphere of European supranationalism. When contrasted against other Union policies, it is immediately clear that EU foreign policy has a special decision-making mechanism, making it highly exceptional.

In the now depillarised framework of the EU treaties, issues of institutional division arise from the legacy of the former pillar system. This is due to the reality that of prime concern in EU external relations is the question of ‘who decides?’ By engaging a number of legal themes, cutting across foreign affairs exceptionalism, executive prerogatives, parliamentary accountability, judicial review, and the constitutionalisation of European integration; the book lays bare how EU foreign affairs has become highly legalised, leading to ever-greater coherence in how Europe exerts itself on the global stage.

In this first monograph dedicated exclusively to the law of the EU’s Common Foreign and Security Policy in modern times, the book argues that the legal framework for EU foreign affairs must adapt in a changing world as to ensure the EU treaties can cater for a more assertive Europe in the wider world.

Published 3 October 2019. 

Order at at:

Hart/Bloomsbury here (20% discount code: CV7).

Amazon here,

Book Despository here,

Waterstones here,

Wildy here.


Butler, G & Sørensen, KE 2020, The Prohibition of Abuse of EU Law: A Special General Principle. in K. Ziegler, P. Neuvonen, & V. Moreno-Lax (eds), Research Handbook on General Principles of EU Law, Research Handbooks in European Law, Edward Elgar: Cheltenham. 

Butler, G 2019 ‘An Interim Post-mortem: Specialised Courts in the EU Judicial Architecture after the Civil Service Tribunal International Organizations Law Review, vol. 16. DOI: 10.1163/15723747-2019010.

Butler, G 2019, The EU Flexibility Clause is Dead, Long Live the EU Flexibility Clause. in A. Bakardjieva Engelbrekt, & X. Groussot (eds), The Future of Europe: Political and Legal Integration Beyond Brexit, Swedish Studies in European Law, Hart Publishing: Oxford. ISBN (Print): 9781509923304 (978-1-5099-2330-4). ISBN (Electronic): 9781509923311 (978-1-5099-2331-1), 9781509923328 (978-1-5099-2332-8), 9781509923335 (978-1-50992-333-5). pp. 63-95. DOI: 10.5040/

Butler, G 2019, United Nations Educational, Scientific and Cultural Organization (UNESCO): The EU’s transition from observer to full participant on an ad hoc basis. in R.A. Wessel, & J. Odermatt (eds), Research Handbook on the European Union and International Organizations, Research Handbooks in International Law, Edward Elgar: Cheltenham. ISBN (Print): 9781786438928 (978-1-78643-892-8). ISBN (Electronic): 9781786438935 (978-1-78643-893-5). pp. 142-164. DOI: 10.4337/9781786438935.00014.

Butler, G 2019, The balance of powers and the EU’s Common Foreign and Security Policy, in D. Fromage, A. Herranz-Surrallés, & T. Christiansen (eds), Executive-legislative (im)balance in the European Union, Parliamentary Democracy in Europe, Hart Publishing: Oxford.  

Butler, G. & Snaith, H. 2019, Negative solidarity: The EU and the financial crisis. in H. Krunke, H. Petersen & I. Manner (eds), Transnational Solidarity: Concept, Challenges and Opportunities, Cambridge University Press: Cambridge. 

Butler, G 2019, Solidaritet og dets grænser for økonomisk integration i EU’s indre marked, EU-ret & Menneskeret, vol. 26, no. 3, pp. 3-27.

Butler, G 2019, Chambers of Deputies. in R Grote, F Lachenmann & R Wolfrum (eds), Max Planck Encyclopedia of Comparative Constitutional Law. Oxford University Press, Oxford. DOI: 10.1093/law-mpeccol/law-mpeccol-e218.

Butler, G & Sadl, U 2018, 'The Preliminaries of a Reference' European Law Review, vol. 43, no. 1, pp. 120-128.

Butler, G 2018, Pre-Ratification Judicial Review of International Agreements to be Concluded by the European Union. in M. Derlén & J. Lindholm (eds), The Court of Justice of the European Union: Multidisciplinary Perspectives, Swedish Studies in European Law, Hart Publishing: Oxford. ISBN (Print): 9781509919086 (978-1-5099-1908-6). ISBN (Electronic): 9781509919093 (978-1-5099-1909-3), 9781509919109 (978-1-5099-1910-9). pp. 53-77.  DOI: 10.5040/

Butler, G & Barrett, G 2018 'Europe’s ‘Other’ Open-Border Zone: The Common Travel Area under the Shadow of Brexit' Cambridge Yearbook of European Legal Studies, vol. 20 no. 1, pp. 252-286. DOI: 10.1017/cel.2018.10.

Butler, G 2018 'Solidarity and its limits for economic integration in the European Union’s internal marketMaastricht Journal of European and Comparative Law, vol. 25, no. 3, pp. 310-331. DOI: 10.1177/1023263X18769207.

Butler, G 2018, 'Legal Responses to the European Union’s Migration Crisis' San Diego International Law Journal, vol. 19, no. 2, pp. 277-310. 

Butler, G 2018, 'In Search of the Political Question Doctrine in EU Law', Legal Issues of Economic Integration, vol. 45, no. 4, 329-354. 

  • Cited in Opinion of Advocate General Michal Bobek, Case C-418/18 P, Puppinck and Others v European Commission, ECLI:EU:C:2019:640, Court of Justice of the European Union (Grand Chamber case).

Butler, G 2018, 'Tvistbilæggelse mellem EU-medlemsstaterne ved Den Europæiske Unions DomstolEuroparättslig Tidskrift, vol. 21, no. 1, pp. 57-74. 

Butler, G 2018, EU Foreign Policy and Other EU External Relations in Times of Crisis: Forcing the Law to Overlap? in E. Kużelewska, A. Weatherburn, D. Kloza (eds), Irregular Migration as a Challenge for Democracy, European Integration and Democracy, Intersentia: Cambridge. ISBN: 978-1-7806-8622-6. pp. 51-81. DOI: 10.1017/9781780687025.005.

Butler, G. 2018, A post-national legal order: Does the European Union have an imposed constitution?. in R. Albert, X. Contiades, A. Fotiadou (eds), The Law and Legitimacy of Imposed Constitutions, Comparative Constitutional Change, Routledge: Abingdon. ISBN (Print): 9781138488984 (978-1-1384-8898-4). ISBN (Electronic): 9781351038980 (978-1-351-03898-0), pp. 227-242.

Butler, G 2018, 'Implementing a Complete System of Legal Remedies in EU Foreign Affairs Law' Columbia Journal of European Law, vol. 24, no. 3, pp. 637-676. 

Butler, G 2017 'The Court of Justice as an inter-state court' Yearbook of European Law, vol. 36, no. 1, pp. 179-208. DOI: 10.1093/yel/yex014

Butler, G 2017 'The Coming of Age of the Court’s Jurisdiction in the Common Foreign and Security Policy' European Constitutional Law Review, vol 13, no. 4, pp. 673-703. DOI: 10.1017/S1574019617000268

Butler, G. 2017, The European Union and Diplomatic Law: An Emerging Actor in Twenty-First Century Diplomacy. in P. Behrens (ed.), Diplomatic Law in a New Millennium. Oxford University Press, Oxford. ISBN: 9780198795940 (978-0-19-879594-0). pp. 319-340. DOI: 10.1093/oso/9780198795940.003.0018.

Butler, G 2017 'Standing the Test of Time: Reference for a Preliminary Ruling' Irish Journal of European Law, vol 20 no. 1, pp. 103-116. Link:

Butler, G 2017, 'A Question of Jurisdiction: Art. 267 TFEU Preliminary References of a CFSP Nature', European Papers, vol 2, no. 1, pp. 201-208. DOI: 10.15166/2499-8249/127

Butler, G. & Jensen, M.D., 2017, Storbritanniens had-kærlighedsforhold til Den Europæiske Union (The United Kingdom's Love-Hate Relationship with the European Union). in C.H. Grøn (ed), Politologisk Årbog 2016-2017 (Political Science Yearbook 2016-2017). Hans Reitzels Forlag, Copenhagen. ISBN-10: 8741269801. ISBN-13: 9788741269801 (978-87-412-6980-1). pp. 20-23. 

Butler, G 2016, Constitutional Limits of the EU's Common Foreign and Security Policy. Ph.D. thesis. 333 pp. 

Butler, G 2016, 'Attacking or Defending? Jurisdiction of the Court of Justice in the EU's Common Foreign and Security PolicyEuroparättslig Tidskrift (Swedish European Law Journal), vol 19, no. 4, pp. 671-684. Link:

Butler, G & Ratcovich, M 2016, 'Operation Sophia in Uncharted Waters: European and International Law Challenges for the EU Naval Mission in the Mediterranean SeaNordic Journal of International Law, vol 85, no. 3, pp. 235-259. DOI: 10.1163/15718107-08503003

  • Cited in Opinion of Advocate General Eleanor Sharpston, Case C-670//16, Tsegezab Mengesteab v Federal Republic of Germany, ECLI:EU:C:2017:480, Court of Justice of the European Union (Grand Chamber case).

Butler, G, Jensen, MD & Snaith, H (eds) 2016, 'British Exit from the EU: Legal and Political Implications' Journal of European Public Policy, vol 23, no. 9, pp. 1278-1328.

Butler, G, Jensen, MD & Snaith, H 2016, '‘Slow change may pull us apart’: debating a British exit from the European UnionJournal of European Public Policy, British Exit from the EU: Legal and Political Implications, Butler, G, Jensen, MD & Snaith, H (eds) vol 23, no. 9, pp. 1278-1284. DOI: 10.1080/13501763.2016.1174527

Butler, G 2016, 'A new means of dissemination for doctoral research in Danish legal education' Retfaerd (Nordic Journal of Law and Justice), vol 39, no. 1/152, pp. 88-95.

Butler, G 2016, 'The Ultimate Stumbling Block? The Common Foreign and Security Policy, and Accession of the European Union to the European Convention on Human Rights' Dublin University Law Journal, vol 39, no. 1, pp. 229-244. 

Butler, G 2015, 'Pinpointing the Appropriate Legal Basis for External Action' European Journal of Risk Regulation, vol 6, no. 2, pp. 323-328.

Butler, G 2015, 'A Political Decision Disguised as Legal Argument? Opinion 2/13 and European Union Accession to the European Convention on Human RightsUtrecht Journal of International and European Law, vol 31, no. 81, pp. 104-111. DOI: 10.5334/ujiel.df

Butler, G 2015, 'The Interparliamentary Conference on the CFSP/CSDP: A new forum for the Oireachtas in Irish and EU foreign policy?Irish Studies in International Affairs, vol 26, pp. 163-186. DOI: 10.3318/isia.2015.26.4

Butler, G 2015, 'Not a “real” common travel area: Pachero v Minister for Justice and EqualityIrish Jurist, vol 54, pp. 155-164.

Butler, G 2015, 'The Road to a Court of Appeal—Part I: History and Constitutional Amendment' Irish Law Times, vol 33, no. 14, pp. 208-211.

Butler, G 2015, 'The Road to a Court of Appeal—Part II: Distinguishing Features and Establishment' Irish Law Times, vol 33, no. 15, pp. 222-226.