Koen Lenaerts (*)
EUnited in Diversity III: the Role of Constitutional Justice in the EU Common Legal Order, Constitutional Court of Bulgaria, Sofia, 3-5 September 2025
President Panova,
Dear Colleagues,
Ladies and Gentlemen,
Welcome to this conference ‘EUnited in Diversity III: the Role of Constitutional Justice in the EU Common Legal Order’, co-organised by the Constitutional Court of Bulgaria and the Court of Justice of the European Union (the ‘Court of Justice’).
This is the third edition of this conference series. The first took place in Riga in 2021, on the initiative of my colleague and friend, Ineta Ziemele,[1] and the second in The Hague in 2023, as a collaborative effort between the Dutch Hoge Raad, the Belgian Constitutional Court and the Luxembourg Constitutional Court.[2]
Today, thanks to the tireless efforts of President Panova and her team, we gather here in the beautiful city of Sofia to discuss four topics over the next two days. The focus of those topics is, to some extent, different from those discussed previously in Riga and in The Hague. That is the result of a deliberate choice by the organisers, who aimed to highlight the fact that the dialogue between the Court of Justice and the Constitutional — or equivalent — Courts of the 27 Member States is not confined to issues relating to fundamental rights.
While fundamental rights are an essential component of that dialogue, they do not provide the full picture of constitutional justice in the EU common legal order. Structural aspects also constitute key components of that dialogue.
In democratic societies, national constitutions lay down a system of checks and balances which seeks to promote and protect the values of respect for liberty, equality, democracy and the rule of law. It is for national Constitutional Courts to uphold that system, by preserving the horizontal and vertical allocation of powers provided for in the constitution. In the EU legal order, the Court of Justice fulfils a similar task, in so far as it also strives to protect the system of checks and balances laid down in the Treaties, which seek to protect and promote the same values.[3]
As James Madison wrote in the Federalist Papers No. 51,[4] the principle of separation of powers and that of conferral (attribution) aim to ensure a ‘double security’ to protect individual liberty. The EU legal order also embraces that approach. Horizontally, the EU institutions must act within the scope of their powers, without upsetting the principle of institutional balance. Vertically, the balance of power between the EU and the Member States as provided for by the Treaties must be safeguarded.
As will be discussed in the first panel, the principle of conferral (attribution) is a means of preserving that balance.[5] Each level of governance – European and national – must operate within its own sphere of competences, without one encroaching upon the policy choices incumbent upon the other. That principle also serves to draw the dividing line between the jurisdiction of the Court of Justice and that of Constitutional Courts.
Yet the EU and the 27 national systems of checks and balances, which constitute the EU’s common legal order, do not function in isolation. The different crises faced by the EU and the 27 Member States have demonstrated that they must work together in order to overcome them. In so doing, the EU and the Member States must remain faithful to the values on which their democracies are founded.[6] As will be discussed in the second panel, it is in times of crisis that our common commitment to those values is truly tested.
Similarly, the European integration process is becoming more complex with EU law and national law interacting in novel ways. This point is illustrated by the emergence of composite administrative procedures,[7] in which acts of national law may operate as preparatory acts under EU law. Within the framework of the Banking Union, for example, a national central bank may propose that the European Central Bank (the ‘ECB’) should object to the acquisition of a bank by another institution whose reputation is questionable. The issue then arises as to which law applies to determine the validity of the national central bank’s proposal and which courts have jurisdiction to rule on that point. In Berlusconi and Fininvest,[8] the Court of Justice held that it is for the EU Courts to examine any defects vitiating the preparatory acts or the proposals of the national central bank that would be such as to affect the validity of the ECB’s decision, provided that the ECB exercises alone the final decision-making power.
More recently, in ECB and Commission v Corneli,[9] the Court of Justice was confronted with a similar issue. In that case, the ECB decided to place an Italian bank under temporary administration on the ground that the situation of that bank was deteriorating significantly, thereby dissolving its administration and supervisory bodies and replacing them by three extraordinary commissioners. In adopting that decision, the ECB exercised its prudential supervision powers. This meant that it had to apply the relevant EU regulations and directives as well as Italian law implementing those directives. The problem was that, unlike the relevant EU directive,[10] Italian law did not expressly provide for such a ground for action. The key question in Corneli was whether the ECB’s interpretation of Italian law was contra legem.
It should be recalled that, where national courts are bound by the duty of consistent interpretation, the question whether the limit of ‘contra legem’ is crossed is ultimately to be determined by the national courts themselves, in compliance with the relevant case law of the Court of Justice.[11] However, in Corneli, it was held that since the relevant duty was imposed on an EU institution, namely the ECB, the EU Courts enjoy jurisdiction to make that determination themselves.
At first instance, the General Court came to the conclusion that the limit of contra legem was breached,[12] since Italian law said nothing about the placement of a bank under temporary administration in the event of a significant deterioration of its situation. As a result, the General Court held that the ECB decision ran counter to Italian law and thus annulled it.
On appeal, the Court of Justice took a different view.[13] It observed that under Italian law, a bank may be placed under temporary administration ‘if serious financial losses are expected’. The Court of Justice considered the expressions ‘significant deterioration’ and ‘serious financial losses’ to be closely related, meaning, in essence, that when one occurs, so does the other. Accordingly, in finding that the ECB decision was indeed consistent with Italian law, the Court of Justice quashed the judgment of the General Court.
These judgments serve to illustrate the fact that EU law and national law are becoming increasingly interconnected and their relationship is becoming more complex. Since the EU and the Member States operate within a shared public space, they must cooperate on the basis of mutual trust. On the one hand, that mutual trust means that the 27 Constitutional – or equivalent – Courts must trust that the Court of Justice upholds the founding values and principles on which the EU is founded when interpreting provisions of EU law. On the other hand, the Court of Justice must trust that national Constitutional Courts will faithfully apply EU law and will not interfere in the dialogue between the Court of Justice and ordinary courts.[14]
In particular, Constitutional Courts should trust the Court of Justice’s firm commitment to the principle of conferral (attribution). The Court of Justice will not hesitate to annul or declare invalid an EU legislative act that is ultra vires because the EU lacks the competence to adopt it,[15] or because, although it enjoys such competence, the EU has failed to exercise it in a manner that complies with the principles of subsidiarity and proportionality,[16] or else because it was not adopted under the correct legal basis.[17] Moreover, the Court of Justice not only checks whether the EU legislature has overstepped the limits of its discretion but also applies a strict version of process-oriented review, according to which the EU legislature must do its ‘homework’ before acting.[18] For example, in the judgment on the Mobility Package,[19] decided last October, the Court of Justice annulled a provision laying down the obligation that required lorries to return to the operational centre of the transport undertaking every eight weeks. In that regard, the Court observed that the EU legislature did not produce, nor did it set out clearly and unequivocally, the basic facts on which the proportionality of the measure was based.[20]
Mutual trust must not be confused with blind trust. That is why, for example, the Court of Justice has ruled that only independent Constitutional Courts may issue judgments that are binding upon ordinary national courts.[21]
That is also why Constitutional Courts, which do not agree with a given judgment of the Court of Justice or wish to raise awareness about a fundamental aspect of their national identity, should engage in a dialogue with the Court of Justice, by means of the preliminary ruling procedure. That is the path followed by the Italian Constitutional Court in the context of the Taricco saga.[22] That is also the path followed by the Latvian Constitutional Court in Cilevičs, which stressed the importance of the Latvian language as an integral part of that Member State’s constitutional identity.[23]
As communication is key, I invite all Constitutional – or equivalent – Courts to enter or, as the case may be, to continue that dialogue.
It is worth noting that so far, 24 out of the 27 Constitutional – or equivalent – Courts of the Member States have made a reference to the Court of Justice.[24]
Moreover, as will be discussed in the third panel, it often happens that the case law of a Constitutional Court is examined in the light of EU law when ordinary courts engage in a dialogue with the Court of Justice. That is the case not only of lower national courts but also of national Supreme Courts where they are separate from Constitutional Courts.
I understand that some Constitutional Courts may feel side-lined, particularly when the crux of a case pending before the Court of Justice concerns their own case law, which is being subjected to external scrutiny. This sense of exclusion is heightened when the order for reference misrepresents or inaccurately reflects that case law.
That is why I must stress the fact that when confronted with complex and unexplored questions of EU law, Constitutional Courts should themselves engage in a dialogue with the Court of Justice. Otherwise, they run the risk of other courts doing it instead of them.
As a second-best alternative, it is worth noting that EU law does not prevent a Member State from establishing internal mechanisms that would enable its own Constitutional Court to make comments or remarks about the way in which its own case law is described in an order for reference. Those internal mechanisms may then compel the government of such a Member State to include those comments in its observations before the Court of Justice. For example, in Melki,[25] the French government drew the attention of the Court to the fact that the French Conseil d’État and Conseil constitutionnel had followed an interpretation of the relevant legislation on the contrôle prioritaire de constitutionnalité, which was different from that put forward by the referring court, the French Cour de cassation. The Court of Justice took into account those observations in its judgment.[26]
Such internal mechanisms have the advantage of preserving the integrity of the dialogue between the Court of Justice and the national court making the reference, while guaranteeing an accurate description of the case law of the Constitutional Court concerned.
Moreover, the fact that a lower or Supreme Court calls into question the case law of its own Constitutional Court certainly does not mean that the Court of Justice will follow suit. Take, for example, the seminal judgment of the Court in the KUBERA case,[27] which will be examined in the fourth and last panel of this conference.
The case involved a reference of the Slovenian Supreme Court, whose case law on the relevant point had been reversed by the Slovenian Constitutional Court.[28] In that case, the Court of Justice was asked to examine the compatibility with the preliminary ruling procedure of a filtering system for bringing matters before the Slovenian Supreme Court (i.e. a leave to appeal system). The Court of Justice ruled that, while EU law does not preclude the Member States from establishing ‘filtering’ systems for bringing matters before the national supreme courts, those systems must meet the requirements deriving from that law and, in particular, the preliminary ruling procedure.[29] In KUBERA, that was not the case, since the Slovenian Supreme Court did not examine whether it was, as a court of last instance, under the obligation to make a reference to the Court of Justice. That being said, the Court observed that it was possible for the Slovenian Supreme Court to change its case law, by having recourse to the duty of consistent interpretation. It came to that finding after noting that the Slovenian Constitutional Court had held that the provision of national law at issue in the main proceedings could be interpreted in a way that enabled the Slovenian Supreme Court to fulfil its obligations under the preliminary ruling mechanism.[30] It is worth noting that, after the Court of Justice delivered its judgment, the Slovenian Supreme Court changed its case law accordingly.[31]
President Panova,
Dear Colleagues,
Ladies and Gentlemen,
The European Union, understood as a common legal order, is founded on the preservation and promotion of common values and structures. To that end, the Court of Justice of the European Union and the Constitutional – or equivalent – Courts of the Member States must work closely together and must trust each other. Only through such cooperation can the EU and the 27 national constitutional orders create the necessary synergies to strengthen democracies, safeguard fundamental rights, and uphold the rule of law across Europe.
Thank you very much.
* * *
(*) President of the Court of Justice of the European Union and Professor of European Union Law, Leuven University. All opinions expressed herein are personal to the author. This opening speech will also appear in the Conference Proceedings, to be published as: ‘EUnited in Diversity: The Role of Constitutional Justice in the EU Common Legal Order’, EUnited in Diversity, Vol. 3, Luxembourg, Court of Justice of the European Union – Publications and Electronic Media Unit (forthcoming).
[1] Conference proceedings, ‘EUnited in Diversity: between common constitutional traditions and national identities’, EUnited in Diversity, Vol. 1, Luxembourg, Court of Justice of the European Union – Publications and Electronic Media Unit, 2021.
[2] Conference proceedings, ‘EUnited in diversity II: The Rule of Law and Constitutional Diversity’, EUnited in Diversity, Vol. 2, Luxembourg, Court of Justice of the European Union – Publications and Electronic Media Unit, 2023.
[3] K. Lenaerts and J.A. Gutiérrez-Fons, ‘The European Union: A Constitutional Perspective’, in R. Schütze and T. Tridimas (eds), Oxford Principles of European Union Law, Vol. 1 (Oxford, OUP, 2018).
[4] See J Madison, ‘The Federalist No 51’ in A. Hamilton, J Madison and J Jay, The Federalist Papers (Oxford University Press 2008) 256 (observing that those two principles give rise to a ‘double security’ to the rights of individuals, because ‘[t]he different governments will control each other [i.e. federalism], at the same time that each will be controlled by itself [i.e., separation of powers]’.
[5] Article 5 TUE. See also K. Lenaerts, ‘Constitutionalism and the Many Faces of Federalism’ (1990) 38 American Journal of Comparative Law 205.
[6] See, in this regard, D. Sarmiento, ‘General Report : Topic I – Emergency Law’ in K. Pacuła (ed), EU Emergency Law – XXXI FIDE Congress |Katowice 2025 Congress, Vol. 1 (Silesia, University of Silesia Press, 2025).
[7] F. Brito Bastos, Judging Composite Decision-Making (Oxford, Hart Publishing, 2024).
[8] Judgment of 19 December 2018, Berlusconi and Fininvest (C‑219/17, EU:C:2018:1023).
[9] Judgment of 15 July 2025, ECB and Commission v Corneli (C‑777/22 P and C‑789/22 P, EU:C:2025:580).
[10] See Directive 2014/59/EU of the European Parliament and of the Council of 15 May 2014 establishing a framework for the recovery and resolution of credit institutions and investment firms and amending Council Directive 82/891/EEC, and Directives 2001/24/EC, 2002/47/EC, 2004/25/EC, 2005/56/EC, 2007/36/EC, 2011/35/EU, 2012/30/EU and 2013/36/EU, and Regulations (EU) No 1093/2010 and (EU) No 648/2012, of the European Parliament and of the Council, [2014] OJ 173/190.
[11] See, in this regard, judgment of 24 June 2019, Popławski II (C‑573/17, EU:C:2019:530), para. 76 and case law cited.
[12] Judgment of 12 October 2022, Corneli v ECB (T‑502/19, EU:T:2022:627), paras 107 and 108.
[13] Judgment of 15 July 2025, ECB and Commission v Corneli (C 777/22 P and C 789/22 P, EU:C:2025:XXX), para. 158.
[14] Judgment of 22 February 2022, RS (Effect of the decisions of a constitutional court) (C‑430/21, EU:C:2022:99).
[15] See, e.g., Opinion 2/94 (Accession of the Community to the ECHR) of 28 March 1996 (EU:C:1996:140), and judgment of 5 October 2000, Germany v Parliament and Council (C‑376/98, EU:C:2000:544). The same applies where an EU administrative measure covers subject matter that is excluded by the EU legislature. See, e.g., judgment of 30 May 2006, Parliament v Council and Commission (C‑317/04 and C‑318/04, EU:C:2006:346. The principle of conferral (attribution) is also upheld where the Court of Justice finds that the EU lacks exclusive competences to act in the realm of external relations. See, in this regard, Opinion 2/15 (Free Trade Agreement with Singapore) of 16 May 2017 (EU:C:2017:376), and judgment of 20 November 2018, Commission v Council (Antarctic MPAs) (C‑626/15 and C‑659/16, EU:C:2018:925).
[16] In the context of fundamental rights protection, the principle of proportionality has led the Court of Justice to declare certain EU measures invalid. See, e.g., judgments of 9 November 2010, Volker und Markus Schecke and Eifert (C‑92/09 and C‑93/09, EU:C:2010:662); of 8 April 2014, Digital Rights Ireland and Others (C‑293/12 and C‑594/12, EU:C:2014:238); of 16 July 2020, Facebook Ireland and Schrems (C‑311/18, EU:C:2020:559), and of 21 March 2024, Landeshauptstadt Wiesbaden (C‑61/22, EU:C:2024:251). See also Opinion 1/15 (EU-Canada PNR Agreement) of 26 July 2017 (EU:C:2017:592).
[17] See, e.g., judgment of 21 March 2024, Landeshauptstadt Wiesbaden (C‑61/22, EU:C:2024:251). In that case, the Court of Justice ruled that Regulation (EU) 2019/1157 of the European Parliament and of the Council of 20 June 2019 on strengthening the security of identity cards of Union citizens and of residence documents issued to Union citizens and their family members exercising their right of free movement was invalid, on the ground that it was adopted under the wrong legal basis. The Court of Justice reasoned that such Regulation should have been adopted under Article 77(3) TFEU (requiring unanimity in the Council), and not under Article 21(2) TFEU (requiring qualified majority in the Council). In that regard, the Court found that the purpose of that Regulation – i.e., to strengthen the security standards applicable to identity cards issued by Member States to their nationals and to residence documents issued by Member States to Union citizens and their family members when exercising their right to free movement – fell within the specific scope of Article 77(3) TFEU. In the aftermath of the Landeshauptstadt Wiesbaden judgment, the EU legislature adopted a new regulation reproducing, in essence, the content of Regulation (EU) 2019/1157 but, this time, with Article 77(3) TFEU as legal basis. See Council Regulation (EU) 2025/1208 of 12 June 2025 on strengthening the security of identity cards of Union citizens and of residence documents issued to Union citizens and their family members exercising their right of free movement, [2025] OJ L, 2025/1208, 20.6.2025.
[18] See, in this regard, K. Lenaerts, ‘The European Court of Justice and Process-Oriented Review’ (2012) 31 Yearbook of European Law 3. See generally X. Groussot and D. Harvey (eds), Process-Oriented Federalism in EU law (Granada, EU Law Live Press, 2024).
[19] Judgment of 4 October 2024, Lithuania and Others v Parliament and Council (Mobility package) (C‑541/20 to C‑555/20, EU:C:2024:818)
[20] Ibid., para. 737.
[21] Judgment of 21 December 2021, Euro Box Promotion and Others (C‑357/19, C‑379/19, C‑547/19, C‑811/19 and C‑840/19, EU:C:2021:1034), para. 232 (holding that ‘EU law does not preclude the establishment of a constitutional court the decisions of which are binding on the ordinary courts, provided that that court complies with the requirements of independence [under Article 19 TEU]’).
[22] Judgments of 8 September 2015, Taricco and Others (C‑105/14, EU:C:2015:555), and of 5 December 2017, M.A.S. and M.B. (C‑42/17, EU:C:2017:936). See also Italian Constitutional Court, Order no. 24/2017. See, in this regard, M. Bonelli, ‘The Taricco saga and the consolidation of judicial dialogue in the European Union’ (2018) 25 Maastricht Journal of European and Comparative Law 357.
[23] Judgment of 7 September 2022, Cilevičs and Others (C‑391/20, EU:C:2022:638). See also Latvian Constitutional Court, judgment of 9 February 2023, Nr.2020-33-01.
[24] AT [judgment of 8 May 2003, Wählergruppe Gemeinsam (C‑171/01, EU:C:2003:260), EU:C:2003:294)], BE [judgment of 29 July 2024, Belgian Association of Tax Lawyers and Others (C‑623/22, EU:C:2024:639)], BG (to date, no reference made), HR [judgment of 16 January 2025, E P (Bourse Erasmus+) (C‑277/23, EU:C:2025:18)], CY (established in 2023), CZ (to date, no reference made), DK [judgment of 19 April 2016, DI (C‑441/14, EU:C:2016:278)], EE [judgment of 15 July 2021, Tartu Vangla (C‑795/19, EU:C:2021:606)], FI [judgment of 10 July 2018, Jehovan todistajat (C‑25/17, EU:C:2018:551)], FR [judgment of 30 May 2013, F. (C‑168/13 PPU, EU:C:2013:358)], DE [judgment of 11 December 2018, Weiss and Others (C‑493/17, EU:C:2018:1000)], GR [judgment of 16 December 2008, Michaniki (C‑213/07, EU:C:2008:731)], HU (to date, no reference made), IE [judgment of 27 November 2012, Pringle (C‑370/12, EU:C:2012:756)], IT [judgment of 6 June 2023, O. G. (European arrest warrant issued against a third-country national) (C‑700/21, EU:C:2023:444)], LV [judgment of 4 October 2024, 1Dream and Others (C‑767/22, C‑49/23 and C‑161/23, EU:C:2024:823)], LT [judgment of 13 November 2019, Lietuvos Respublikos Seimo narių grupė (C‑2/18, EU:C:2019:962)], LU [judgment of 8 March 2017, ArcelorMittal Rodange et Schifflange (C‑321/15, EU:C:2017:179)], MT [judgment of 20 April 2021, Repubblika (C‑896/19, EU:C:2021:311)], NL [judgment of 8 November 2022, Staatssecretaris van Justitie en Veiligheid (Ex officio review of detention) (C‑704/20 and C‑39/21, EU:C:2022:858)], PL [judgment of 7 March 2017, RPO (C‑390/15, EU:C:2017:174)], PT [order of the President of the Court of 26 October 2021, VectorImpacto – Automóveis Unipessoal (C‑136/21, not published, EU:C:2021:925)], RO [judgment of 5 June 2018, Coman and Others (C‑673/16, EU:C:2018:385)], SK [judgment of 11 June 2020, Prezident Slovenskej republiky (C‑378/19, EU:C:2020:462)], SI [judgment of 27 February 2025, AEON NEPREMIČNINE and Others, (C‑674/23, EU:C:2025:113)], ES [judgment of 26 February 2013, Melloni (C‑399/11, EU:C:2013:107)], SE [judgment of 26 October 2021, PL Holdings (C‑109/20, EU:C:2021:875)].
[25] Judgment of 22 June 2010, Melki and Abdeli (C‑188/10 and C‑189/10, EU:C:2010:363).
[26] Ibid., paras 48 to 50.
[27] Judgment of 15 October 2024, KUBERA (C‑144/23, EU:C:2024:881).
[28] Ibid., paras 24 et seq.
[29] Ibid., para. 32.
[30] Ibid., para. 54.
[31] Vrhovno sodišče, Sklep z dne 29/01/2025, Dossier QP/13082-P1.
