Can a National Referendum Delay Eurozone Accession – the Bulgarian Experience?

I. Factual background 

On 8th of July 2025, Bulgaria was officially admitted to the Euro area, with entry effective as from 1st of January 2026¹.

The process preceding this approval generated significant debate within the Bulgarian political and legal spheres. In 2023, a group of 49 Members of Parliament (MPs) submitted a request to the Constitutional Court to review Parliament’s decision of 7th of July  2023, concerning the non-conduct of a referendum on joining the Euro area. The MPs challenging the decision supported a civil initiative aimed at asking voters whether the Bulgarian lev should remain the sole currency in Bulgaria until 2043. The Constitutional Court rejected this request through Decision No. 3/2024, citing several arguments. The core argument supported the thesis that Bulgaria had given preliminary consent to participate in the monetary union as a condition for its membership in the European Union.

Despite the aforementioned decision, on 12th of May 2025, Bulgarian President Rumen Radev submitted another request to Parliament to decide on a new referendum concerning the adoption of the European currency in Bulgaria. The draft question submitted by the President pertained to entry into the Euro area as of 2026. However, by Ruling No. 51-550-01-301/13.05.2025, Parliament’s President rejected this request as inadmissible.

Following this, the President of Bulgaria, as the requesting party, submitted two further questions for interpretation by the Constitutional Court. The first question deals with whether the Bulgarian Parliament is obliged by the Constitution to vote on a referendum request submitted by an authorized state body. The second concerns the empowerment of Parliament’s President to decline referendum requests made by a state body, as provided by law.

By Ruling No. 3 from 10th of June 2025 the Constitutional Court rejected the first question and concentrated the case on the second query. The rejection of the first question has been justified with the argument that the Constitutional Court is merely empowered to interpret the Constitution but not the law giving the framework how Bulgarian Parliament operates (The Parliament’s Houserules). The proceedings are still pending.

II. The legal debate surrounding the request for referendums 

The Bulgarian Constitution does not provide a detailed regulation on how national and local referendums should take place. Article 84, paragraph 4 of the Constitution merely states that Parliament has the power to adopt a decision on whether a national referendum should take place or not. Further provisions on the organization and other matters of referendums are set out in the Act on the Direct Participation of Citizens in the Local and Central Government (ADPCLCG)². It also provides what the legal consequences are if the question in the referendum has been answered positively. In those cases, the Bulgarian Parliament is required to enforce the will of the people through the new legislation.  

The main argument of the euro opponents who support the requests for a referendum stems from the provision of Article 10, paragraph 2 of the ADPCLCG. It limits the decision-making power of Parliament if more than 400,000 Bulgarian citizens have signed a petition for conducting a referendum and if it does not contravene the restrictions imposed by the ADPCLCG. These restrictions include, for example, matters of international treaty already ratified by Bulgaria or if it concerns the amount of tax or social security contributions.

In Decision No. 3/2024³, the Constitutional Court states that if a matter is the subject of an international treaty—for example, the Treaty on European Union, the Treaty on the Functioning of the European Union, or the Treaty concerning the Accession of the Republic of Bulgaria and Romania to the European Union—it cannot be questioned in a national referendum. This is because the Bulgarian Parliament is unable to unilaterally amend an international treaty. Thus, the scope of such referendums is considered very limited by the Bulgarian constitutional order. Such referendums could be admissible only if Bulgaria has not yet signed or ratified the treaty, and they could include questions on whether the treaty should be adopted or not, or a derogation (if such could be negotiated by the signing state at all).

The second argument of the euro-referendum supporters is that it could not lead to an amendment of the existing EU law, since Article 140 of the TFEU does not provide an exact date for waiving the derogation. In fact, it just gives an overview of the financial stability of the member state and its ability to join the Euro area. It has further merely the role to establish if a member-state with a derogation has changed its political will and amended the respective banking and currency legislation. Thus, a referendum related to the entry date into the euro area would not affect the legal consistency of the treaty. This is a controversial idea hidden behind a formal argument that the lack of an exact date for entering the Eurozone means that any member state could decide alone on admittance into the currency union even after all steps towards the admittance have been undertaken. 

European integration represents a dynamic and long-lasting process that can be accelerated or slowed down by a member state by fulfilling certain criteria. As an example of the latter Sweden is considered. For more than 20 years it has not fulfilling willingly the criteria, i.e., it is not undertaking any steps towards the synchronization of its Central Bank legislation with European law. However, this was a result of a non-binding referendum held in 2003 and the following anti-euro course taken by the ruling parties in the Scandinavian country. It shows an approach which is different to the Bulgarian one since the majority of the parties forming the governmental coalition in Bulgaria have initiated all steps, including legislative changes, necessary for the adoption of the common currency.  

The Swedish experience shows that integration into the currency union could be slowed down or avoided intentionally, but this could not happen as a result of a binding referendum establishing obligations for the country parliaments or governments to renegotiate the treaties. It is the clear purpose of the antieuropean parties in the Bulgarian Parliament not merely to slow down European integration but also to undertake all steps to quit the European Union. Instead, it could be a political reaction of a member state before the fulfillment of the admittance criteria, in which case the predominant political players would have to unite on such a course and make objective attempts against the fulfillment of the criteria set out by Article 140 of the TFEU.

The Bulgarian situation is different. On 29th of June 2018 the minister of finance and the director of the Bulgarian Central Bank submitted an official request that Bulgaria would like to join the ERM II currency mechanism. The member state has been admitted to the said mechanism on 10th of July 2020. Thus, it could be concluded that Bulgaria has willingly fulfilled the objective criteria set out in the primary European law. Hereby the most important criteria for entering the euro area are to be regarded as fulfilled. This reflects also the position of the Bulgarian Constitutional court which considers the entrance into the currency union as a preagreed (in terms of the Admission Treaty) condition of the membership in the European Union and further appearance of the successful European integration. 

Apart from that, it is widely accepted within Bulgarian constitutional jurisprudence⁴ that merely the act of Parliament which has been adopted can be subject to constitutional control, and not the matter as such. Given this, it is not possible for the Constitutional Court to rule abstractly on whether conducting a referendum on entry into the Euro area contradicts the Bulgarian Constitution or not.

In this context, it was not a big surprise that Bulgarian President Radev again challenged the country’s entrance into the common European currency area in May 2025, in order to gain political influence among the nationalist wing and start again the legal debate on the admissibility of a referendum which could postpone the admittance to the Euro zone even if the chances of success of such challenge are not big given the previous jurisprudence of the Constitutional Court.  

Despite the lack of a political majority ready to vote for a new referendum, the President of the Bulgarian Parliament, Natalia Kiselova (herself a professor of constitutional law), made a strategic mistake and did not process the request made by President Radev. This resulted in a situation where the Constitutional Court would have to elaborate on the constitutional role of the President of the National Assembly and the question of whether he could unilaterally reject a request for a referendum submitted by a state body authorized by law to do so. The outcome of such an interpretation of the Constitution could not be foreseen, as the Constitution has no provisions dealing with the constitutional role of the Parliament’s President.

III. Conclusion 

The position of the Bulgarian Constitutional Court confirms firmly that the integration of Bulgaria as a member state of the EU has been already predetermined by the membership itself. If Bulgaria has consented to the criteria set forth in the treaties, redefining the structure of the European integration and the content of the treaties is not an option on which the Bulgarian parliament and the Bulgarian voters could decide. Thus, the Bulgarian Parliament has to reject all requests made by state bodies or civil initiatives, even if large group of people, e.g. more than 400 000, support such referendum irrespectively whether it questions the admittance to the euro zone as such or the moment in which the country could become a part of it. 

However, the decision could be certainly criticized in the aspect concerning the lack of possibility for the Bulgarian citizens to give their opinion on aspects of the European integration process since it deprives them from the ability to influence political decisions concerning the role of Bulgaria during the European integration process. 

The adoption of the euro could be a hot political topic during the next few months (even a year), but it no longer represents a decisive legal issue. The euro is coming, and it is almost certain that everybody will use it as the state currency in Bulgaria starting from the beginning of 2026.

1. Council Regulation (EU) 2025/1408 of 8 July 2025 amending Regulation (EC) No 974/98 as regards the introduction of the euro in Bulgaria,OJ L 2025/1408,14.7.2025,E LI: http://data.europa.eu/eli/reg/2025/1408/oj.
2. DV (Darzhaven vestnik, i.e. State Gazette)  Nr. 44 from 12.6.2009, last amended DV Nr. 15 from 22. 2. 2022.
3. Decision No. 3 from 8.2.2024 of the Constitutional Court, DV No. 15 from 14. 2. 2024.
4.  Decision No. 9 from 28. 7. 2016, DV No. 60 from 2.8.2016.