The adoption of the euro in bulgaria from a legal point of view.
Image taken by: Patrick Fore.
I. INTRODUCTION
The adoption of the Euro is one of the most significant steps in European integration. It symbolizes the unity of Member States by adopting the same currency, a phenomenon which would have been foolish to imagine just 40 years ago. However, there are rising questions about whether the adoption of the euro is a political choice or a legal obligation. The most recent issue regarding the adoption of the universal European currency arose in Bulgaria. The country, which joined the European project in 2007, officially adopted the euro in 2026, becoming the 21st Member State of the Eurozone after fulfilling the convergence criteria. Therefore, Bulgaria’s accession to the euro area raises an important legal question, was this step a matter of political discretion, or was it the fulfillment of a binding legal obligation under EU law? In this article, I will examine whether, from a legal perspective, Bulgaria was obliged under EU law to adopt the euro, or whether it retained a legal right to indefinitely postpone accession to the Eurozone. Furthermore, Bulgaria’s 2005 Accession Treaty and its domestic constitutional legal framework will be taken into consideration.
II. THE LEGAL FRAMEWORK OF THE ECONOMIC AND MONETARY UNION
The Economic and Monetary Union (EMU) is a fundamental objective of the European Union established in Article 3(4) of the Treaty on European Union, which states that the Union shall establish a monetary union whose currency is the euro. Additionally, Articles 119–140 of the Treaty on the Functioning of the European Union provide us with the detailed “legal architecture” for EMU. Why is Article 119 important? It is the provision which sets the EU’s commitment to maintain a stable and competitive economy by coordinating national budgets and maintaining the stability of the euro. By imposing a level of discipline, Article 119 explains why the EU can set limits on national deficits and why the European Central Bank focuses on keeping the inflation rate around 2%.
Article 139 of the TFEU makes the distinction between Member States whose currency is the euro and those with a “derogation”. There are specific rules that do not apply to non-euro countries enshrined in this article. For instance, countries outside the Eurozone do not get to vote on specific euro-related issues such as:
· The European Central Bank (ECB): They do not participate in the main monetary policy decisions of the European Central Bank.
· Sanctions: They are not involved in deciding whether a euro area country should be fined for having excessive debt.
· Exchange Rates: They do not participate in setting the exchange rate of the euro against foreign currencies (such as the dollar or yen).
Furthermore, because they keep their own currencies, the non-euro States are not held to strict “eurozone-only” standards, such as the direct management of the euro in the international context. Without Article 139, there would be legal uncertainty regarding the status of non-euro Member States.
Article 140 is the provision that lists all the economic requirements. They are designed to prove that a country’s economy is stable enough to handle the euro. The established conditions to be met are:
a) Price Stability (Inflation) – The inflation rate cannot be more than 1.5% higher than that of the three best-performing EU countries.
b) Sound Public Finances – There must not be an “excessive deficit.” Usually, this means the yearly budget deficit is under 3% of GDP and total public debt is under 60% of GDP.
c) Exchange Rate Stability – The national currency must have remained stable against the euro (in ERM II) for at least two years without devaluation.
d) Long-term Interest Rates – Long-term interest rates cannot be more than 2% higher than those of the three best-performing countries.
Every two years, the European Commission and the European Central Bank prepare a “Convergence Report” (Article 140(1)) and submit it to the Council to assess how non-euro countries are progressing towards achieving Economic and Monetary Union. Article 140 is important because it serves as the final step for joining the Eurozone and ensures that countries are sufficiently stable before fulfilling their legal obligation.
III. WHY SOME MEMBER STATES ARE NOT IN THE EUROZONE. THE “OPT-OUTS”
Not all Member States are part of the Eurozone, and this is a well-known fact. The main question is why they are not. Some do not meet the requirements set out in Article 140, while others negotiated explicit opt-outs (a legal exemption that allows an EU country to skip specific rules, such as adopting the euro, while remaining in the Union). The most prominent example is Denmark, which secured a permanent opt-out from the third stage of EMU through an additional protocol formally attached to the Treaty of Maastricht (1992). An interesting fact is that Denmark, thanks to its opt-outs, can also opt out of certain EU rules on police and justice cooperation.
Previously, the United Kingdom also held a formal opt-out before leaving the EU. In contrast, countries such as Poland, Hungary, Czechia, Sweden, and Romania do not possess formal opt-outs. They remain outside the eurozone either because they have not fulfilled the convergence criteria or, in Sweden’s case, because they have chosen not to enter ERM II (Exchange Rate Mechanism – a mechanism that stabilizes the transition from a national currency to the euro; a country enters ERM II voluntarily to begin the final phase of joining the euro).
However, from a legal standpoint, these states remain under a derogation rather than enjoying a permanent exemption. The absence of an opt-out means that euro adoption remains a treaty obligation once the conditions are satisfied. Bulgaria never negotiated an opt-out; therefore, it falls into this second category.
IV. THE 2005 ACCESSION TREATY AND BULGARIA’S COMMITMENT, DOMESTIC LEGISLATION AND CONSTITUTIONAL COMPATIBILITY
It is important to mention the 2005 Treaty concerning the Accession of the Republic of Bulgaria and Romania to the European Union. By signing and ratifying this treaty, Bulgaria accepted the entire body of EU primary law, including the provisions on Economic and Monetary Union (thereby expressing the willingness to work towards achieving the core objective in Article 3(4) TEU). Therefore, the Accession Treaty did not provide Bulgaria with a special exemption from EMU but placed it among Member States with a temporary derogation under Article 139 TFEU. In other words, euro adoption was foreseen from the moment of accession, and the only factor preventing Bulgaria from joining the Eurozone immediately was the convergence criteria.
A further question concerns whether euro adoption potentially contradicts Bulgarian domestic law, particularly the Constitution of Bulgaria. The Bulgarian Constitution establishes the Bulgarian National Bank (BNB) as the central monetary authority of the State. However, as an EU Member State, Bulgaria is required to align its national legislation with EU law, including provisions on central bank independence and integration into the European System of Central Banks. Article 5(4) of the Bulgarian Constitution states that international treaties ratified and promulgated in accordance with constitutional procedures become part of domestic law and take precedence in case of conflict with national legislation. Since the EU Treaties were ratified in accordance with this article, EU monetary law forms part of Bulgaria’s internal legal order.
Moreover, the principle of primacy of EU law, as established by the Court of Justice of the European Union in cases such as Costa v ENEL (important EU case from 1964), requires national authorities to give precedence to EU law over conflicting domestic provisions. Furthermore, although euro adoption transfers monetary competence to the European Central Bank, this transfer is legally authorized by Bulgaria’s Accession Treaty. Therefore, euro adoption does not constitute an “unconstitutional surrender” of sovereignty, as some critics in Bulgaria suggest, but rather the exercise of sovereignty through treaty commitments.
Although no case directly addresses a refusal to adopt the euro, the Court of Justice has consistently emphasized the binding nature of EMU rules. In Pringle v Government of Ireland (Case C-370/12), the Court described EMU as an essential component of the EU’s constitutional structure. Furthermore, in Gauweiler (Case C-62/14) and Weiss (Case C-493/17), the Court confirmed the exclusive competence of the EU in monetary policy for euro area states. These judgments underline that participation in the eurozone entails a lawful transfer of monetary sovereignty to the EU level. Applied to Bulgaria, this jurisprudence reinforces the conclusion that euro adoption is not a political option, but a legally structured obligation embedded within EU primary law (*TEU and TFEU form the EU primary law).
V. CONCLUSION
From a strictly legal perspective, Bulgaria’s adoption of the euro was not discretionary but rather an obligation under EU law. By joining the Union, Bulgaria expressed its willingness to be legally bound by EU law and to work towards the establishment of the core objective in Article 3(4) TEU. While there were no negotiated opt-outs, such as in the case of Denmark, and Bulgaria remained subject to a temporary derogation under Article 139 TFEU. Once the convergence criteria were met and the derogation was lifted, Bulgaria completed its full integration into the European Monetary Union. In other words, Bulgaria’s adoption of the euro represents the legal fulfillment of commitments undertaken at the moment of EU accession. And from now on it is the States’s policies, with the help of the European Central Bank and the other regulators, that will shape Bulgaria’s new monetary policy and future economic development.
Author: Boris Atanasov (Law student at Sofia University and Global Law student at the University of Turin)
E-mail: borisatanasov22@gmail.com
LinkedIn: Boris Atanasov
BIBLIOGRAPHY
Primary Sources
Treaties
Treaty on European Union (TEU) [2012] OJ C326/13. - https://eur-lex.europa.eu/resource.html?uri=cellar:2bf140bf-a3f8-4ab2-b506-fd71826e6da6.0023.02/DOC_1&format=PDF
Treaty on the Functioning of the European Union (TFEU) [2012] OJ C326/47. - https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:12012E/TXT:en:PDF
Treaty concerning the Accession of the Republic of Bulgaria and Romania to the European Union [2005] OJ L157/11. - https://enlargement.ec.europa.eu/system/files/2018-12/act_of_accession_bulgaria_romania_en.pdf
Protocol (No 16) on Certain Provisions Relating to Denmark, annexed to the Treaty on European Union and the Treaty on the Functioning of the European Union.
Cases
Case 6/64 Costa v ENEL [1964] ECR 585. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex:61964CJ0006
Case C-370/12 Pringle v Government of Ireland EU:C:2012:756. - https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex:62012CJ0370
Case C-62/14 Gauweiler and Others v Deutscher Bundestag EU:C:2015:400. - https://eur-lex.europa.eu/legal-content/BG/TXT/?uri=CELEX:62014CJ0062
Case C-493/17 Weiss and Others EU:C:2018:1000. - https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex:62017CJ0493
EU Institutional Documents
European Commission, Convergence Reports (Specifically the one of Bulgaria from 2025).
https://economy-finance.ec.europa.eu/publications/convergence-report-2025-bulgaria_en
National Law
Constitution of the Republic of Bulgaria (1991, as amended).
