–Jinlin Hu, Undergraduate student in Bulgarian Studies, Beijing Foreign Studies University
Introduction
On 1 January 2026, Bulgaria officially adopted the euro as its new currency. For the EU, this represents a routine step in European integration, fulfilling a promise undertaken by Bulgaria upon its accession to the EU in 2007. Beneath the apparent smoothness of this accession, however, lies a persistent constitutional friction surrounding the adoption of the euro.
Unlike when Bulgaria first joined the EU, public opinions today are markedly more skeptical of the concept of further European integration and are increasingly distrustful of the purported benefits. These concerns crystallized in repeated attempts to trigger a national referendum aimed at postponing the adoption of the euro until 2043. Yet by the time these initiatives emerged, the legal status of euro adoption had already acquired a degree of finality. In this way, popular sovereignty clashes with international treaty obligations.
The Bulgarian Constitutional Court (the Court) addressed the conflict in its core ruling on this matter in 2024 (Decision No. 3/2024), which upheld the National Assembly’s (the Assembly) refusal to call a national referendum on the matter of adopting the euro. However, though the judgment is procedurally sound and justified, the Court’s decision to ensure the smooth adoption process may well be the result of a legal compromise. This post argues that the Court’s decision should be understood not as a straightforward application of constitutional hierarchy, but as a conscious constitutional trade-off in which the Court curtailed procedural expressions of popular sovereignty in order to preserve Bulgaria’s substantive capacity to act as a full monetary sovereign within the EU.
The Referendum Challenge and Bulgaria’s Binding International Obligations
In the 2024 ruling, the petitioner put forward two principal claims on which this post focuses: (1) the Assembly lacks the competence to adopt a decision rejecting a proposal for holding a national referendum; and (2) the question contained in the proposal complies with the Constitution, especially with the principle of popular sovereignty.
Before ruling on the merits of these claims, the Court first emphasizes the governing principle of the rule of law in the present case.
According to Articles 1(2) and 4(1) of the Constitution, Bulgaria is a modern state where power derives from the people and is governed by the Rule of Law. The Court maintains, following Decision No. 9/2016, that while the people are the source of power, they have “voluntarily placed themselves under the action of the Constitution” (para. 28). This creates a hierarchical mechanism of self-binding: the sovereign people, as the constituent power, established the Constitution as a supreme framework that limits their own actions as a constituted power. Consequently, the “will of the sovereign” expressed through a referendum cannot bypass this framework; the rule of law serves as a jurisdictional gatekeeper that prevents the “misappropriation of sovereignty” by ensuring that direct democracy operates only within the boundaries of the Constitution.
Regarding the petitioner’s first claim, therefore, the Court distinguishes between the initiation and the outcome of a referendum. It acknowledges that a referendum, involving the direct exercise of state power, “directly decides the question posed” (para. 31), and under Article 84(5), the National Assembly is legally bound by the final result. However, the Court rejects the notion that the Assembly is automatically bound to approve any proposal that meets the 400,000-signature threshold (para. 32). Instead, the Assembly acts more like as a constitutional filter (para. 34). As the representative of the people, the Assembly has a mandatory duty to independently assess whether the referendum question complies with the substantive values of the Constitution, specifically the rule of law and existing legal obligations. Consequently, the petitioner’s first claim is unfounded.
Moving on to the constitutionality of question on the adoption of the euro, the Court points out two factors relevant to the holding of a national referendum. First, the enforceability of the question to be put to the people (para. 61). As previously noted, given that a decision adopted in a referendum constitutes the direct exercise of power, whatever choice the public makes in a referendum must be implemented. Thus, if the decision adopted through a national referendum is non-enforceable, the Assembly will be unable to fulfill its legal obligations, which constitutes a breach of the principle of the rule of law.
When Bulgaria signed the Treaty of Accession to the European Union (the Treaty) in April 2005, it did not merely join a trade bloc; rather, it accepted the entire Acquis Communautaire, including the obligation to eventually adopt the euro. Under Article 85 of the Bulgarian Constitution, the Assembly ratifies international treaties, which then become part of the domestic legal order and take precedence over conflicting domestic legislation. Therefore, as long as Bulgaria is a member state of the EU, it is bound by the Union’s founding treaties and is not permitted to unilaterally amend, suspend or change an international treaty (para. 67).
Consequently, contrary to what the petitioner had argued, the Act on Direct Citizen Participation in State and Local Government (ADCPSLG) could not be used to trigger a referendum on a topic covered by the European Treaties. Once a treaty is ratified and the delegation of sovereignty to the EU has taken effect, the resultant international norms preempt all other domestic laws, as per Article 5(4) of the Bulgarian Constitution.
Secondly, the Court indicates that Bulgaria’s membership status is that of a Member State with a derogation. When signing the Accession Treaty, Bulgaria promised to adopt the euro once the convergence criteria set out in Article 140(1) TFEU were met. As such, this participation was a fulfillment of its accession obligations rather than a discretionary choice that could be reversed by a popular vote. In this way, the Court sees this status as an irrevocable commitment to join the European Monetary Union (para. 75). Therefore, a national referendum seeking to postpone this obligation until 2043 is not merely a “clarification” of the treaty’s content but a constitutionally inadmissible attempt to unilaterally modify international obligations. Again, such an act would violate the principle of the rule of law and the separation of powers under Article 4(3) and Article 85(3) of the Constitution.
A Legal Compromise that Must be Made
The Court is justified in maintaining Bulgaria’s international obligations by invoking the principle of the rule of law enshrined in the national Constitution. However, its reasoning is also vulnerable to criticism.
As mentioned, the Court considers the Constitution as the ultimate embodiment of the common values agreed by all Bulgarian people, therefore no other values or principles should supersede it. In its defense of irrevocable treaty obligations, the Court sought to argue that even when the exercise of state power occurs directly by the people as the sovereign, failing to adhere to the Accession Treaty’s obligations would mean non-fulfillment of the state’s constitutional commitment (para. 92), with constitutionalism requiring the placement of the people under the law they created (para. 93). In this view, the Court is essentially expressing that Bulgaria has made a pre-commitment, and the will of the people was fully exercised and exhausted at the moment of accession. But this attitude seems somewhat passive as it might be neglecting genuine popular objection, thereby damaging the country’s own democratic nature.
It is instructive to contrast the Bulgarian Court’s reasoning with that of the German Federal Constitutional Court in its Lisbon Urteil, in which it famously rejected the legitimization of the European Union as a federal state, insisting instead that sovereignty remains vested in the Member States. European integration was held to be constitutionally permissible only insofar as it preserves the German people’s capacity for democratic self-determination through the German parliament.1 To this end, the German Court articulated two safeguards: constitutional identity review and ultra vires review, both designed to ensure that integration does not hollow out the democratic substance protected by the German Basic Law. It is in this way that the German Court can ensure the principle of popular sovereignty will not be eroded or eased out in international decision-making.
Whereas the Bulgarian Court frames the adoption of the euro as the legal consequence of an irrevocable international commitment, the German Court conceptualizes integration as a conditional process grounded in democratic authorization by a sovereign state. In this sense, the German Court takes the role of an active agent in preserving the power of the people. But in essence, the Bulgarian Court’s “passivity” does not mean that it does nothing; it actively chooses to be “pro-integrationist,” while Germany is more cautious to European integration.
Bulgaria is not as economically and politically power in the EU as Germany. Since 1997, Bulgaria has operated under a currency board arrangement, pegging the Bulgarian lev first to the Deutsch Mark, then, after the euro became the legal tender of Germany, to the euro. For nearly three decades, Bulgaria has lived in a state of “monetary limbo”: it has undertaken much of the responsibility as a member of the European Central Bank (ECB) while having zero say in the ECB’s decisions (para. 83).
In this light, the Court’s “passive” stance is in fact a pragmatic recognition of the constitutional and economic reality. To allow a referendum on a choice that has long been settled in practice risks destabilizing a monetary framework that had already shaped Bulgaria’s fiscal policy for decades. The “compromise” here is that by officially surrendering a degree of sovereignty that was already functionally lost, Bulgaria can finally participate in ECB’s decision-making.
In addition, amid internal political instability and demonstrable right-wing populism in the country,the Court sought to contain the risk of constitutional incoherence arising from popular votes within the bounds of Bulgaria’s existing international commitments by compromising short-term public volatility in exchange for long-term economic and legal credibility.
The Maturity of a Bound Sovereign
In saying that the Bulgarian Court might have pursued a legal compromise in deciding the referendum case, I acknowledge that in a modern, integrated democracy, popular sovereignty is not the right to make a new choice every day, but the strength to honor the choices made previously and collectively. The Bulgarian case suggests a new principle for European integration: democratic self-government depends not on the constant re-opening of foundational choices, but on the principled fulfillment of sovereign promises. The euro adoption process is not just changing a currency; it is how a mature sovereign secures its future by transforming a self-imposed constraint into an active seat at the table of European governance.
Suggested citation: Jinlin Hu, A Legal Compromise That Must Be Made? Behind Bulgaria’s Euro Adoption, Int’l J. Const. L. Blog, Feb. 14, 2026, at: http://www.iconnectblog.com/a-legal-compromise-that-must-be-made-behind-bulgarias-euro-adoption/
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The purpose of a Democracy is to select the people to make decisions. Not every decision those people make is going to be individually popular. The model is to allow the population to select the mood and direction of the country. In this case, the Democractic decision was for the country to join up with other European countries. This will inevitably have outcomes some of which are popular, some are unpopular, and some divide opinion.
It is also for the Democratically elected people to decide when a topic is to be passed to a Referendum vote – as the court notes, there is not a legal requirement for Referenda to be held. The political stance on Euro adoption was clear when the Bulgarian Government was elected.
In any case, it is mostly older people who disfavor the Euro adoption so demographically there is an argument that the results of a referendum are simply a transient snapshot.