National Identity, Same-Sex Marriage, and Union Citizenship: Slovakia's Preliminary Reference to the CJEU

https://doi.org/10.63189/JCTM2000

A commentary on the preliminary reference of the Constitutional Court of the Slovak Republic lodged with the Court of Justice of the European Union on 12 August 2026, in a case concerning the loss of Slovak, and thereby Union, citizenship following a same sex marriage concluded outside the European Union.

On 14 August 2026, the Constitutional Court of the Slovak Republic (Ústavný súd Slovenskej republiky, hereinafter also the Constitutional Court) announced that it had referred a preliminary question to the Court of Justice of the European Union (hereinafter also CJEU or Court of Justice). The reference was formally lodged with Luxembourg on 12 August 2026, after the Second Senate at a non public sitting on 1 July 2026 stayed proceedings on a constitutional complaint and submitted a question under Article 267 of the Treaty on the Functioning of the European Union.^[1] "Is Article 21(1), read in conjunction with Article 20(1), of the Treaty on the Functioning of the European Union to be interpreted as precluding an interpretation of a national provision under which a citizen of the European Union loses his or her State citizenship, and thereby also citizenship of the European Union, if he or she enters into marriage with a person of the same sex in a State which is not a Member State of the European Union, by reason of the acquisition of a foreign nationality on the basis of an express expression of will, where, under national law, loss of citizenship would not occur if the marriage were concluded between persons of different sex?" - that is the wording of the preliminary question. The request for a preliminary ruling was submitted to the Court of Justice of the EU on 12 August of this year.

The question is unusually narrow, and precisely for that reason politically charged. A Slovak citizen, born in Slovakia and long resident in the United Kingdom, married his male partner there and, in consequence of that marriage, was naturalised as a British citizen. He informed the Slovak Embassy in London that he wished to retain his Slovak citizenship. He was told that he had lost it, and with it citizenship of the European Union, and was ordered to surrender his Slovak identity documents. Slovak law provides an express exception under which citizenship is not lost when foreign nationality is acquired through marriage. The Ministry of the Interior refused to apply that exception, on the ground that Slovak law recognises marriage only as a union between a man and a woman.^[2]

The Constitutional Court asks whether Articles 20(1) and 21(1) TFEU preclude such a reading of national law. The question is about citizenship, not about marriage. It is nonetheless a question in which the two are entangled, and the answer will matter beyond Slovakia. The substantive Slovak definition of marriage is constitutionally protected; therefore the reference was legally correct and procedurally unavoidable, at the same time the case exposes a genuine drafting weakness in Slovak citizenship law that the September 2025 constitutional amendment neither caused nor cured.

The facts and the applicable Slovak law

Public reporting identifies the complainant as a thirty-four-year-old Slovak citizen, publicly known as Lukáš, from central Slovakia, who married his British partner on 28 August 2022 in the United Kingdom.^[3] The Constitutional Court’s press release does not name the complainant, but media sources do.^[4]

The applicable Slovak instrument is Act No. 40/1993 Coll. on the Citizenship of the Slovak Republic. Section 9(16) provides that a Slovak citizen loses citizenship if he or she voluntarily acquires foreign nationality, subject to an express spousal exception in Section 9(17), under which loss does not occur where foreign nationality is acquired during a marriage together with the foreign spouse.^[5] The Ministry of the Interior takes the view that this exception cannot apply where the foreign marriage is between persons of the same sex, because Slovak family law and, since 2014, the Slovak Constitution recognise marriage exclusively as a union between a man and a woman.^[6] That definition is not a recent political innovation but the codification of a legal and cultural understanding that has run through Slovak law without interruption.

The result is a legal outcome that we should find analytically striking. A Slovak who marries a foreigner abroad, and who acquires the foreign spouse’s nationality in consequence, retains Slovak citizenship if the spouse is of the opposite sex, and forfeits it if the spouse is of the same sex. The Constitutional Court frames the question exactly this way and asks Luxembourg whether Union law tolerates that differential outcome.^[7]

Why the Constitutional Court had to refer, not decide

There is a widespread misconception, on both sides of the debate, that a preliminary reference is a kind of surrender, a national court outsourcing a hard question to Brussels. That misconception should be laid to rest, and the Constitutional Court itself preempted it in its press release.

Under Article 267(3) TFEU, a national court against whose decisions there is no judicial remedy under national law is obliged to refer a question of Union law to the Court of Justice, unless the correct answer is obvious, has already been settled in the Court’s case law, or the question is irrelevant to the outcome. This is the doctrine of acte clair and acte éclairé, recently reaffirmed in Consorzio Italian Management.^[8] The Slovak Constitutional Court is such a court of last instance in the constitutional complaint procedure. It correctly notes that submitting a preliminary question in these circumstances is not a matter of discretion but of duty.^[9]

The question posed is not obvious and definitely not settled. The interaction between Union citizenship, national nationality law, and non-recognition of foreign same sex marriages is a genuinely open area. Deciding without referring would have exposed Slovakia to state liability under Köbler^[10] and to infringement risk under Commission v France for judicial breaches of the reference obligation.^[11] The reference is therefore not a political choice. It is a legal reflex, and a healthy one for a court that takes its European obligations seriously without conceding anything about domestic constitutional substance.

It is worth being precise, because the political discussion in Slovakia has already run ahead of the legal question. The reference does not ask the Court of Justice to require Slovakia to recognise same sex marriage. It does not ask the Court to require Slovakia to open marriage to same sex couples in its domestic law. It does not ask about registration of a foreign same sex marriage in Slovak civil registers, nor about permanent residence for a same sex spouse, nor about parental status. Those are separate questions, some of which are pending before other fora.

The question is single, and narrower: whether the state may, by operation of a purely domestic definition of marriage, strip a Union citizen of Union citizenship in circumstances in which an otherwise identical opposite sex marriage would leave that citizenship intact.

The September 2025 constitutional amendment in the background

The reference cannot be read outside the constitutional context that Slovakia itself created in the autumn of 2025. Constitutional Act No. 255/2025 Coll., adopted by the National Council on 26 September 2025 with the minimum ninety votes required and in force from 1 November 2025, added two paragraphs to Article 7 of the Slovak Constitution asserting Slovak sovereignty over “matters of national identity”, expressly including marriage, parenthood, and family, together with an interpretive clause that nothing in the Constitution shall be read as consent to transfer the exercise of Slovak competences in those matters.^[12] The amendment also constitutionalised the recognition of only two biologically determined sexes and reserved adoption to married heterosexual couples.^[13]

This is a legitimate expression of national constitutional identity. Article 4(2) TEU obliges the Union to respect the national identities of its Member States, “inherent in their fundamental structures, political and constitutional”, and the definition of marriage and family sits at the core of what Slovak constitutionalism has always claimed as its own. The provisions are not a novelty imposed on Slovak society but a constitutional codification of commitments that Slovak law, and Slovak public opinion across successive electoral cycles, has long affirmed. To treat their enshrinement in the Constitution as an act of hostility toward Europe is to misread both Slovak legal history and the pluralism that Article 4(2) TEU was drafted to protect. Central European scholarship has argued that constitutional identity clauses of this kind function not as anti European provocations but as anchors that allow European integration to proceed on terms compatible with democratic self government.^[14]

What the amendment does not do, and cannot do, is redraw the scope of Union citizenship under Article 20 TFEU. The Slovak Constitutional Court’s reference is a direct acknowledgment of that limit, and the acknowledgment is made from a position of institutional confidence rather than deference. The definition of marriage in Article 41 of the Slovak Constitution, and the sovereignty clause in Article 7, govern what Slovakia recognises as marriage. They do not govern whether Union law permits a Member State to translate its non recognition of a foreign marriage into a loss of Union citizenship for one of its own nationals. That translation is what the Court of Justice will be asked to assess.

The Union has never claimed a competence to define marriage. The Slovak spousal exception in Section 9(17) is drafted in terms of manžel and manželka, a linguistic pairing that fits a heterosexual union. The Ministry of the Interior can argue, with textual support, that the exception was drafted against a domestic legal background in which marriage meant one thing, and that extending it to a legal relationship the domestic order does not recognise is a matter for the legislature, not for administrative interpretation. The Constitutional Court itself has emphasised that the applicability of the exception is precisely the question the case turns on.^[15]

Prediction is risky in Luxembourg, but some observations are safe enough to venture in the register of a scholarly commentary. The Court of Justice is unlikely to instruct Slovakia to recognise same sex marriage in its domestic legal order. That is not the question the Constitutional Court has asked, and the Court has been careful, in Coman and elsewhere, to circumscribe its rulings. Even so, Coman itself was already a contested extension of the Free Movement Directive, and a further step into nationality law, where Member State competence is at its most exclusive, would be difficult to reconcile with the Court's own case law on the limits of Union competence.

A ruling that overreached would fracture its authority on the terrain, national identity, where it is most contested. More probable is a reaffirmation that Member States define the conditions of loss of nationality, but must do so with due regard to Union law and to the proportionality principle. That is a settled starting point since Rottmann, and it will hold. Alongside it, one should expect an insistence on some form of individualised proportionality assessment before Slovak citizenship can be extinguished in the circumstances described in the reference. This can be framed in ways that leave Slovak sovereignty intact on the definition of marriage while requiring that the ministry either apply the spousal exception or provide a specific, individualised justification for not doing so in a case where the only material distinction is the sex of the spouse.

Concluding observations

Central European constitutional courts have, for three decades, been asked to reconcile two loyalties, the loyalty to a domestic constitutional order and the loyalty to a European legal order the Member State has chosen to join. The Slovak reference belongs to that tradition. It is not a surrender of the first loyalty to the second, but the acknowledgment that the second exists. The substantive definition of marriage in the Slovak Constitution is not on trial. That definition remains a matter of Slovak constitutional identity, protected by Article 4(2) TEU, and Union law has neither claimed nor is being asked to claim a power to change it. The September 2025 constitutional amendment is an assertion of that identity, and its sovereignty clause in Article 7(6) and (7) is a serious constitutional statement. That statement rests on a view of the family that Slovakia has repeatedly affirmed. It reflects an understanding, shared across much of Central Europe, that the family unit is not a variable of policy but a pre-political institution which the Constitution recognises and protects, rather than invents. Whether one shares that understanding or not, it is a legitimate premise of a democratic constitutional order, and one that Article 4(2) TEU was designed to accommodate rather than to override.

Where the case gets interesting is not the marriage question at all, but the citizenship question. The spousal exception in Section 9(17) exists to prevent Slovak citizens from being penalised for the ordinary fact of marrying a foreigner. Whether that exception can be denied to a Slovak citizen for reasons that have nothing to do with the acquisition of the second nationality, and everything to do with the sex of the spouse, is a legitimate question. That legitimate question, it must be emphasised, is a technical one about the drafting of Section 9(17) of the Act on Citizenship, not a challenge to the substantive commitments the Slovak Constitution makes about marriage and family. The outcome that best preserves Slovak interests may be the one that decouples the marriage question from the citizenship question. A ruling that requires proportionality without requiring recognition would leave the constitutional definition of marriage intact, prevent the sex of a spouse from serving, on its own, as the operative ground for the loss of Union citizenship, and return the political discussion to the National Council. This approach is compatible with the deepest instincts of Central European constitutionalism, which have always understood that sovereignty and rule of law are allies rather than rivals. A rule of law that applies only when the outcome is politically congenial is not a rule of law. It is a rule of preference, dressed in the vocabulary of the rule of law. By referring, the Constitutional Court has kept faith with both loyalties it owes, to the Slovak legal order and to the European one. The answer, when it arrives, will not resolve the underlying moral and political disagreements about marriage that continue to divide European societies, and it is not the business of the Court of Justice to resolve them. What it may resolve, and resolve narrowly, is the question of whether a Member State's own definition of marriage can be enlisted to withdraw Union citizenship from one of its own nationals. The substantive commitments of the Slovak Constitution about marriage, family, and national identity are unaffected by the reference, and will remain unaffected by the answer.

^[1] Ústavný súd Slovenskej republiky, Ústavný súd sa obrátil na Súdny dvor EÚ s prejudiciálnou otázkou [The Constitutional Court has turned to the Court of Justice of the EU with a reference for a preliminary ruling] (Press Release No. 26/2026, Bratislava, 14 August 2026) <https://www.ustavnysud.sk/> accessed 14 August 2026. SITA, Ústavný súd sa obrátil na Európsky súdny dvor s prejudiciálnou otázkou, týka sa manželstiev osôb rovnakého pohlavia (SME, 14 August 2026) https://www.sme.sk/domov/c/ustavny-sud-sa-obratil-na-europsky-sudny-dvor-s-prejudicialnou-otazkou-tyka-sa-manzelstiev-osob-rovnakeho-pohlavia accessed 14 August 2026.

^[2] Ústavný súd Slovenskej republiky (n 2); The Slovak Spectator, A Slovak married the love of his life and became British. Then Slovakia stripped him of his citizenship (Spectator, 25 April 2024) https://spectator.sme.sk/politics-and-society/c/a-slovak-married-love-of-his-life-and-became-british-then-slovakia-stripped-him-of-his-citizenship accessed 14 August 2026; Magazín Kontext, ESĽP komunikoval Slovensku sťažnosť, ktorá otvára otázku uznávania manželstiev osôb rovnakého pohlavia (Magazín Kontext, 2026) https://magazinkontext.sk/eslp-komunikoval-slovensku-staznost-ktora-otvara-otazku-uznavania-manzelstiev-osob-rovnakeho-pohlavia/ accessed 14 August 2026.

^[3] The Slovak Spectator (n 3).

^[4] Ústavný súd Slovenskej republiky (n 2).

^[5] National Council of the Slovak Republic, Act No. 40/1993 Coll. on the Citizenship of the Slovak Republic, as amended, s 9(16) and (17).

^[6] Constitution of the Slovak Republic, No. 460/1992 Coll. (as amended).

^[7] Ústavný súd Slovenskej republiky (n 2); Standard.sk, Ústavný súd žiada výklad EÚ v prípade straty slovenského občianstva (Standard, 1 August 2026) https://standard.sk/1277283/ustavny-sud-ziada-vyklad-eu-v-pripade-straty-slovenskeho-obcianstva accessed 14 August 2026.

^[8] Case C 561/19 Consorzio Italian Management and Catania Multiservizi (CJEU, Grand Chamber, 6 October 2021) ECLI:EU:C:2021:799.

^[9] Ústavný súd Slovenskej republiky (n 2).

^[10] Case C 224/01 Köbler v Republik Österreich (CJEU, 30 September 2003) ECLI:EU:C:2003:513.

^[11] Case C 416/17 European Commission v French Republic (CJEU, 4 October 2018) ECLI:EU:C:2018:811.

^[12] Ústavný zákon č. 255/2025 Z. z., ktorým sa mení a dopĺňa Ústava Slovenskej republiky č. 460/1992 Zb. v znení neskorších predpisov https://www.epi.sk/zz/2025-255 accessed 14 August 2026; European Commission for Democracy through Law (Venice Commission), Slovak Republic — Urgent Opinion on the Draft Amendments to the Constitution, Opinion No. 1255/2025, CDL-PI(2025)011 (Strasbourg, 24 September 2025) <https://www.venice.coe.int/webforms/documents/default.aspx?pdffile=CDL-PI(2025)011-e> accessed 15 August 2026; TASR, Parliament passes constitutional amendment with 90 votes (TASR, 26 September 2025) https://www.tasr.sk/tasr-clanok/TASR:2025092600000174 accessed 14 August 2026; Reuters, Slovakia amends constitution to promote ‘national identity’ (Reuters, 26 September 2025) https://www.reuters.com/world/slovakia-amends-constitution-promote-national-identity-2025-09-26/ accessed 14 August 2026.

^[13] Amnesty International and others, Joint Open Letter on New Constitutional Amendments Adopted in Slovakia (16 October 2025) <https://www.amnesty.eu/wp-content/uploads/2025/10/Joint-open-letter-on-new-Constitutional-amendments-adopted-in-Slovakia-1.pdf> accessed 15 August 2026.; Garayová, L. (2025). Slovakia’s 2025 constitutional amendment: Traditional values and national identity in the constitution.Central European Researchers’ Blog, Oct 25, 1–5. https://doi.org/10.63189/HKMA4624, accessed 14 August 2026.

^[14] Garayová, L. (2025). (n 14).

^[15] Ústavný súd Slovenskej republiky (n 2).

References

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