Economic and Monetary Union: Legal Foundations and the Structure of European Economic Integration

Economic and Monetary Union: Legal Foundations and the Structure of European Economic Integration

1. Introduction

Economic and Monetary Union (EMU) is one of the most significant constitutional and economic achievements of the European Union. It represents an advanced form of integration in which Member States coordinate their economic policies, participate in common economic governance arrangements and, where they have adopted the euro, share a single currency and a centralised monetary policy.

The creation of EMU was motivated by the recognition that a deeply integrated internal market could not operate as effectively if exchange-rate instability, divergent monetary policies and incompatible economic strategies repeatedly disrupted cross-border trade and investment. A common currency would remove exchange-rate risks between participating countries, reduce transaction costs, increase price transparency and strengthen economic interdependence.

However, monetary union involves more than replacing national currencies with the euro. It requires a common institutional structure, rules governing monetary authority, mechanisms for economic coordination and safeguards designed to preserve financial and fiscal stability.

The legal architecture of EMU is established principally by Articles 119–144 of the Treaty on the Functioning of the European Union (TFEU), supplemented by provisions concerning the European Central Bank, the European System of Central Banks, the euro and the Union’s economic governance framework.

The resulting structure is distinctive. Monetary policy for euro-area countries is centralised and conducted by the European Central Bank (ECB) and the Eurosystem. Economic policy, taxation and public expenditure remain substantially national responsibilities, although Member States must coordinate their policies and comply with common fiscal and economic rules.

Consequently, EMU is not a complete fiscal or political union. It combines a single monetary authority with decentralised national budgetary powers and an increasingly developed system of economic surveillance.

Understanding this distinction is essential to understanding both the achievements and the structural challenges of European economic integration.

2. Historical Development of Economic and Monetary Union

The development of EMU was gradual. Its origins can be traced to the early attempts to coordinate European monetary policies and reduce exchange-rate instability following the establishment of the European Economic Community.

2.1 Early monetary cooperation

During the 1960s, European governments began examining the possibility of closer monetary integration. The Werner Report of 1970 proposed a gradual movement towards economic and monetary union, although the international monetary instability of the early 1970s prevented its implementation.

In 1979, the European Monetary System (EMS) was established. Its principal mechanism, the Exchange Rate Mechanism (ERM), sought to reduce fluctuations between participating European currencies.

The EMS represented an important step towards monetary cooperation, but it did not create a single currency or transfer monetary policy to a common European institution.

2.2 The Delors Report

In 1988, the European Council commissioned a committee chaired by Jacques Delors, then President of the European Commission, to examine how economic and monetary union could be achieved.

The resulting Delors Report proposed a three-stage process involving:

• Liberalisation of capital movements and closer monetary cooperation.
• Establishment of institutions and procedures preparing the Union for monetary integration.
• Introduction of a single currency and a common monetary policy.

This framework provided the foundation for the negotiations that led to the Maastricht Treaty.

2.3 The Maastricht Treaty

The Treaty on European Union, signed at Maastricht in 1992, established the legal and institutional foundations of EMU.

It introduced the convergence criteria governing admission to the euro area, established the framework for a European central banking system and set out the timetable for the introduction of the single currency.

The Maastricht settlement also reflected a political compromise. Member States agreed to centralise monetary policy for participating countries but retained substantial responsibility for national economic and fiscal decisions.

This division remains one of the defining characteristics of EMU.

2.4 The introduction of the euro

The third stage of EMU began on 1 January 1999. Exchange rates between participating currencies were irrevocably fixed, and the euro became the common currency for monetary and accounting purposes.

Euro banknotes and coins entered circulation on 1 January 2002.

The euro area subsequently expanded as additional Member States satisfied the legal and economic conditions for adoption.

As of November 2026, twenty-one EU Member States use the euro. Bulgaria adopted the currency on 1 January 2026, becoming the twenty-first member of the euro area.

3. The Three Stages of EMU

The traditional three-stage model remains important for understanding the institutional development of monetary union.

3.1 Stage One: Economic preparation (1990–1993)

The first stage began on 1 July 1990.

Its principal objectives included:

• Removing restrictions on capital movements between Member States.
• Strengthening cooperation between national central banks.
• Improving economic convergence.
• Increasing coordination of monetary policies.

The liberalisation of capital movements was particularly important because monetary integration required a more open and interconnected financial environment.

3.2 Stage Two: Institutional preparation (1994–1998)

The second stage began on 1 January 1994.

The European Monetary Institute (EMI) was established to prepare the institutional and technical framework for the single currency. It was the predecessor of the European Central Bank.

National central banks were required to move towards greater independence, and Member States were expected to strengthen economic convergence.

The Treaty also introduced restrictions on monetary financing of public authorities and privileged access to financial institutions, laying important foundations for the monetary discipline of the future euro area.

3.3 Stage Three: Monetary union (1999 onwards)

The third stage began on 1 January 1999.

Its principal elements included:

• Irrevocable fixing of exchange rates between participating currencies.
• Introduction of the euro as a single currency.
• Establishment of the ECB’s responsibility for the common monetary policy.
• Operation of the Eurosystem.
• Implementation of the Stability and Growth Pact.
• Development of common economic surveillance mechanisms.

Unlike the first two stages, the third stage remains an ongoing process because not every EU Member State has adopted the euro.

4. Treaty Foundations: Articles 119–144 TFEU

The principal legal framework for EMU is contained in Title VIII of the TFEU, entitled Economic and Monetary Policy.

Article 119 establishes the basic structure of the Union’s economic and monetary activities.

It provides that Member States and the Union must pursue economic policies based on close coordination, the internal market and common objectives, conducted in accordance with the principle of an open market economy with free competition.

The provision also establishes the euro as the Union’s single currency and provides for a single monetary and exchange-rate policy for participating Member States.

The primary objective of that monetary policy is to maintain price stability. Without prejudice to this objective, monetary policy must support the general economic policies of the Union.

Article 119 therefore expresses the fundamental distinction between the economic and monetary dimensions of EMU.

Economic policies remain subject to coordination among Member States. Monetary policy for euro-area countries is conducted through a common institutional system.

Other important Treaty provisions include:

• Article 120: General principles governing the economic policies of Member States.
• Article 121: Multilateral surveillance and coordination of economic policies.
• Article 122: Measures addressing serious economic difficulties and exceptional circumstances.
• Article 123: Prohibition of monetary financing.
• Article 124: Prohibition of privileged access to financial institutions.
• Article 125: The prohibition of assuming another Member State’s financial commitments.
• Article 126: The excessive deficit procedure.
• Article 127: Objectives and tasks of the European System of Central Banks.
• Articles 130–131: Central bank independence and compatibility of national legislation.
• Articles 136–138: Special arrangements for euro-area Member States.
• Article 140: Assessment of convergence before adoption of the euro.

The Treaties are supplemented by protocols, particularly Protocol No 4 on the Statute of the European System of Central Banks and the European Central Bank, Protocol No 12 on the excessive deficit procedure, Protocol No 13 on the convergence criteria and Protocol No 14 on the Eurogroup.

Together, these provisions establish the constitutional structure of monetary integration and the limits within which national economic policies operate.

5. The Distinction Between Economic Union and Monetary Union

Economic union and monetary union are closely connected but are not identical.

Economic union involves the coordination of national economic policies, the operation of the internal market, common regulatory frameworks and mechanisms intended to promote sustainable economic development.

Monetary union involves the adoption of a single currency and the centralisation of monetary policy.

All EU Member States participate in the economic dimension of EMU through the Treaties and the relevant coordination mechanisms. Only euro-area countries participate in the single monetary policy.

This distinction has important consequences.

A Member State outside the euro area retains its national currency and conducts its own monetary policy through its national central bank, subject to the applicable EU framework.

A Member State within the euro area no longer determines its own independent monetary policy or exchange rate against other euro-area currencies. Those responsibilities belong to the common monetary system.

However, euro-area membership does not transfer all economic powers to the Union. National governments continue to decide their budgets, taxation systems, public expenditure priorities and many structural economic policies, subject to EU law and economic governance obligations.

EMU is therefore a system of shared and differentiated economic responsibilities rather than a fully centralised economic government.

6. The European Central Bank and the Eurosystem

The European Central Bank is the central institution responsible for monetary policy in the euro area.

It was established in 1998 and became operational in connection with the beginning of the third stage of EMU.

Its legal foundations are contained in Articles 127–133 and 282–284 TFEU and Protocol No 4.

6.1 The European System of Central Banks

The European System of Central Banks (ESCB) consists of the ECB and the national central banks of all EU Member States.

The ESCB includes central banks of countries that have not adopted the euro.

Its institutional structure reflects the fact that the Treaties establish a Union-wide framework for monetary cooperation, even though the single monetary policy applies only to euro-area countries.

6.2 The Eurosystem

The Eurosystem consists of the ECB and the national central banks of Member States whose currency is the euro.

It is the system responsible for conducting the single monetary policy.

The distinction is essential:

• The ESCB includes the ECB and every EU national central bank.
• The Eurosystem includes the ECB and the central banks of euro-area countries.

The ECB’s Governing Council is the principal decision-making body for monetary policy.

It consists of the members of the Executive Board and the governors of the national central banks of euro-area Member States.

6.3 Primary objective: Price stability

Article 127(1) TFEU establishes price stability as the primary objective of the ESCB.

The Treaty does not define a numerical inflation target. The ECB’s monetary policy strategy gives practical meaning to this objective.

The ECB currently defines price stability through a symmetric two per cent inflation target over the medium term, measured by the Harmonised Index of Consumer Prices.

The symmetry of the target means that inflation above and below two per cent are considered equally undesirable deviations from the objective.

Without prejudice to price stability, the Eurosystem must support the general economic policies of the Union.

These may include objectives such as sustainable growth, employment, technological development and environmental protection, provided that support for them does not compromise the primary monetary objective.

6.4 Monetary policy instruments

The ECB uses several instruments to implement monetary policy.

The principal instruments include:

• Key interest rates.
• Open market operations.
• Lending facilities for eligible financial institutions.
• Deposit facilities.
• Minimum reserve requirements.
• Asset purchase and other monetary policy programmes where justified by the ECB’s mandate.

Changes in monetary policy rates influence borrowing costs, credit conditions, savings decisions, investment and aggregate demand.

The transmission of monetary policy is not identical in every Member State. National banking structures, financial markets and economic conditions may affect the speed and strength of its effects.

Nevertheless, the common monetary policy is intended to operate across the euro area as a whole.

7. Independence of the European Central Bank

The independence of the ECB is a fundamental feature of the monetary union.

Article 130 TFEU prohibits the ECB, national central banks and members of their decision-making bodies from seeking or taking instructions from EU institutions, national governments or other bodies when performing their Treaty tasks.

EU institutions and national governments must also respect this principle and must not seek to influence members of the ECB’s decision-making bodies in the performance of their duties.

The independence requirement is intended to protect monetary policy from short-term political pressures, particularly pressures to manipulate interest rates or monetary conditions for electoral or immediate fiscal purposes.

It does not mean that the ECB is free from legal constraints or democratic accountability.

The ECB remains bound by the Treaties, the principle of conferral, proportionality, fundamental rights and judicial review by the Court of Justice.

It also reports on its activities and participates in regular monetary dialogue with the European Parliament.

The institutional balance therefore combines operational independence with legal accountability.

8. The Euro and the Legal Status of the Single Currency

The euro is the common currency of the euro-area Member States.

Article 128 TFEU gives the ECB the exclusive right to authorise the issuance of euro banknotes within the Union, while the ECB and national central banks may issue such notes.

Euro coins are issued by Member States, subject to approval by the ECB of the volume of issuance.

Article 133 TFEU provides the legal basis for measures necessary for the use of the euro as the single currency, without prejudice to the ECB’s powers.

The euro also has a wider international role. It is used as a reserve currency, a means of international payment and a unit of account in financial and commercial transactions.

The legal significance of the euro extends beyond the physical currency. Its introduction required the irrevocable fixing of conversion rates between participating national currencies and the establishment of a single monetary policy.

Once a Member State adopts the euro, it cannot independently devalue its currency against other euro-area currencies because it no longer has a separate national currency.

This makes economic adjustment more dependent on domestic economic conditions, labour-market flexibility, productivity, fiscal policy and structural reforms.

9. Economic Policy Coordination: Articles 120 and 121 TFEU

Unlike monetary policy, economic policy remains primarily within national competence, although Member States must coordinate their policies at Union level.

Article 120 requires Member States to conduct their economic policies with a view to contributing to the objectives of the Union and within the framework of the broad guidelines adopted under Article 121.

Article 121 establishes the multilateral surveillance procedure.

The Council, on the basis of recommendations from the Commission, adopts broad economic policy guidelines for Member States and the Union.

Member States must inform the Council and Commission of important economic policy measures and provide other information necessary for multilateral surveillance.

The Commission monitors economic developments and assesses whether national policies are consistent with the common guidelines and the proper functioning of EMU.

Where a Member State’s economic policy is inconsistent with the guidelines or risks jeopardising the functioning of EMU, the Council may address recommendations to that Member State.

The procedure is an important expression of the balance between national responsibility and collective economic governance.

The Council does not ordinarily replace national governments as the decision-maker for domestic economic policy. It coordinates, monitors and recommends corrective action within the Treaty framework.

10. The Stability and Growth Pact

The Stability and Growth Pact (SGP) is one of the central instruments of EU economic governance.

It was developed to reinforce the Treaty requirements concerning sound public finances and to prevent excessive government deficits and debt from threatening the stability of monetary union.

The Pact applies to all Member States, although certain corrective mechanisms and sanctions are specific to euro-area countries.

10.1 The reference values

Protocol No 12 establishes two important reference values:

• A government deficit of 3% of gross domestic product.
• Government debt of 60% of gross domestic product.

These values are central to the excessive deficit procedure under Article 126 TFEU.

They should not be understood as an automatic prohibition on every temporary deviation. The Treaty and secondary legislation establish assessment criteria, relevant circumstances and procedures for determining whether an excessive deficit exists.

The debt criterion also allows consideration of whether the debt ratio is sufficiently diminishing and approaching the reference value at a satisfactory pace.

10.2 Preventive and corrective arms

The Stability and Growth Pact traditionally operates through two complementary components.

The preventive arm aims to prevent fiscal difficulties before they develop into excessive deficits.

The corrective arm addresses situations where public finances breach the relevant Treaty requirements and an excessive deficit procedure is initiated.

The framework has evolved considerably since its original introduction, particularly following the sovereign debt crisis and the subsequent reforms of EU economic governance.

10.3 The 2024 reform

The EU adopted a major reform of its economic and fiscal governance framework in April 2024. The new rules entered into force on 30 April 2024.

The reform introduced a system based on national medium-term fiscal-structural plans and country-specific net expenditure paths.

The principal legislative instruments include:

• Regulation (EU) 2024/1263 on the effective coordination of economic policies and multilateral budgetary surveillance.
• Regulation (EU) 2024/1264 amending the excessive deficit procedure framework.
• Directive (EU) 2024/1265 amending the requirements for national budgetary frameworks.

The reform seeks to combine sustainable public finances with investment, structural reform and economic growth.

Rather than relying exclusively on short-term annual fiscal adjustments, the new framework provides for medium-term fiscal planning.

Member States submit plans generally covering four or five years, setting out their fiscal trajectories, reform commitments and investment priorities.

The Commission assesses these plans, and the Council adopts recommendations establishing the relevant fiscal paths.

The system is intended to accommodate differences in national debt levels and economic conditions while maintaining the common requirements of fiscal sustainability.

11. The Excessive Deficit Procedure

Article 126 TFEU establishes the excessive deficit procedure (EDP).

It is designed to prevent and correct excessive government deficits and debt levels that may threaten the stability of the Union’s economic and monetary system.

The procedure involves several stages.

The Commission monitors budgetary developments and public debt levels. Where it identifies a risk of excessive deficit, it prepares a report and examines the relevant economic circumstances.

The Economic and Financial Committee provides an opinion.

If the Commission considers that an excessive deficit exists or may occur, it addresses an opinion to the Member State and informs the Council.

The Council then determines whether an excessive deficit exists and may issue recommendations requiring corrective action.

Where the Member State fails to take effective action, the procedure may progress to more formal steps.

For euro-area Member States, Article 126(11) permits the application of sanctions in the circumstances established by the Treaty and relevant legislation.

These may include requirements to publish additional information before issuing bonds, requests for reassessment of lending policy by the European Investment Bank, non-interest-bearing deposits or fines under the applicable framework.

The procedure demonstrates that fiscal sovereignty is not unlimited within EMU. National governments retain budgetary authority but must exercise it consistently with common fiscal obligations.

12. The European Semester

The European Semester is the principal annual framework for coordinating and monitoring economic, fiscal, employment and social policies across the Union.

It was introduced in response to weaknesses in economic coordination exposed by the financial and sovereign debt crises.

The Semester brings together several monitoring and coordination processes that were previously more fragmented.

Its principal elements include:

1. Analysis of the economic situation and identification of common priorities.
2. Examination of national fiscal and economic policies.
3. Assessment of national reform and budgetary plans.
4. Country-specific recommendations.
5. Monitoring of implementation.

The Commission publishes an annual assessment of economic and social developments and identifies policy priorities.

Member States submit the relevant national plans and information, allowing the Commission and Council to assess fiscal sustainability, structural reforms, investment and economic imbalances.

Country-specific recommendations are then adopted by the Council.

These recommendations are not equivalent to national legislation and do not automatically replace domestic budgetary decisions. However, they form part of the economic governance obligations and surveillance process established by EU law.

The European Semester is therefore a mechanism of coordinated governance rather than a centralised European budgetary authority.

13. The Macroeconomic Imbalance Procedure

Fiscal deficits are not the only source of economic instability.

A Member State may have a balanced public budget while experiencing serious economic weaknesses, such as excessive private-sector borrowing, an unsustainable housing boom, declining competitiveness or persistent external imbalances.

The Macroeconomic Imbalance Procedure (MIP) was introduced to identify and address such risks.

It is based principally on Regulation (EU) No 1176/2011.

The Commission uses an alert mechanism and an economic scoreboard to identify developments requiring closer examination.

Relevant indicators may include:

• Current-account balances.
• Net international investment positions.
• Export market shares.
• Unit labour costs.
• Private-sector debt.
• Public-sector debt.
• House prices.
• Unemployment.
• Credit growth.

Where the Commission identifies a potential imbalance, it may conduct an in-depth review.

If an imbalance exists, the Council may issue recommendations.

Where excessive imbalances are identified, the procedure can become more demanding. For euro-area countries, the corrective framework may include an excessive imbalance procedure and, in specified circumstances, financial sanctions.

The MIP recognises that monetary union creates economic interdependence. Developments in one Member State may affect financial stability, demand and competitiveness elsewhere.

14. Monetary Financing and the Prohibition on Bailouts

Two Treaty provisions are particularly important to the constitutional structure of EMU: Articles 123 and 125 TFEU.

14.1 Article 123: Prohibition of monetary financing

Article 123 prohibits overdraft facilities and other credit facilities from the ECB or national central banks in favour of EU institutions, Member State governments, regional or local authorities and certain other public bodies.

It also prohibits the direct purchase of debt instruments from those public authorities by the ECB or national central banks.

The provision is designed to prevent governments from financing public expenditure through direct central bank credit.

It protects monetary discipline and the independence of monetary policy.

The prohibition does not mean that every ECB purchase of government bonds is unlawful. The Court of Justice has recognised that secondary-market purchases may be compatible with Article 123 where they comply with the Treaty requirements and do not circumvent the prohibition on direct monetary financing.

14.2 Article 125: The no-bailout clause

Article 125 TFEU provides that the Union and Member States are not liable for or entitled to assume the commitments of another Member State’s public authorities or public undertakings.

The provision is commonly described as the no-bailout clause.

Its purpose is to preserve incentives for responsible national fiscal policy and prevent governments from assuming that other Member States will automatically discharge their financial obligations.

However, Article 125 does not prohibit every form of financial assistance.

In Pringle v Government of Ireland, Case C-370/12, the Court of Justice examined the compatibility of the European Stability Mechanism with EU law.

The Court held that Article 125 does not prohibit financial assistance where the beneficiary Member State remains responsible for its financial commitments and the assistance is subject to conditions designed to encourage sound economic policies.

The judgment is central to understanding the legal relationship between fiscal responsibility, solidarity and financial stability within monetary union.

15. The Eurogroup and Euro-Area Governance

The Eurogroup is the informal forum in which finance ministers of euro-area Member States discuss matters relating to their shared currency and economic policies.

Its legal basis is recognised in Protocol No 14 to the Treaties.

The Eurogroup does not replace the Council of the European Union or exercise the ECB’s monetary powers.

It provides a political forum for coordination, discussion and preparation of decisions concerning the euro area.

The Eurogroup also has an important role in the management of economic crises and the development of common approaches to fiscal and economic policy.

Its President is elected by the finance ministers of euro-area countries for a renewable term.

The existence of the Eurogroup reflects the differentiated structure of EMU: all Member States participate in the broader economic coordination framework, but euro-area countries have additional common interests and responsibilities arising from their shared currency.

16. Financial Stability, Banking Union and the European Stability Mechanism

The financial crisis demonstrated that a monetary union requires more than common interest rates and fiscal surveillance.

Financial institutions operate across national borders, and weaknesses in national banking systems may threaten the stability of the wider euro area.

The EU therefore developed additional mechanisms to strengthen financial supervision, crisis management and banking stability.

16.1 Banking Union

The Banking Union is an important component of the institutional development of EMU.

It is based on three principal pillars, although the third remains incomplete.

The Single Supervisory Mechanism (SSM) gives the ECB direct supervisory responsibility over significant banks in participating Member States and a broader oversight role over the banking system.

The Single Resolution Mechanism (SRM) provides a framework for resolving failing banks while seeking to minimise disruption to financial stability and the use of public funds.

The third proposed pillar, a European Deposit Insurance Scheme, has not yet been completed.

Banking Union is particularly important because monetary policy cannot operate effectively if financial instability in one Member State repeatedly threatens the banking systems of others.

16.2 The European Stability Mechanism

The European Stability Mechanism (ESM) is an intergovernmental financial assistance mechanism established by the euro-area Member States.

It provides financial assistance to euro-area countries experiencing or threatened by severe financing difficulties, subject to the conditions established by the ESM Treaty.

The ESM is not an ordinary EU institution established under the TFEU. It operates through a separate international treaty concluded by participating Member States.

Its legal relationship with EU law was examined in Pringle, Case C-370/12.

The ESM illustrates the development of crisis-management mechanisms beyond the original Treaty architecture of EMU.

17. Member States Outside the Euro Area

Not all EU Member States participate in the euro area.

The Treaties distinguish between Member States whose currency is the euro and those benefiting from a derogation.

Article 139 TFEU identifies Member States that have not adopted the euro and whose position differs from that of euro-area countries.

Such Member States remain subject to important aspects of economic coordination and surveillance but do not participate fully in the single monetary policy.

Their national central banks are members of the ESCB but not the Eurosystem.

17.1 The obligation to adopt the euro

Most EU Member States are expected to adopt the euro once they satisfy the relevant legal and economic conditions.

Denmark is the exception because it has a Treaty-based opt-out.

Other Member States have a derogation, meaning that they have not yet met the conditions or completed the necessary legal process for adopting the euro.

The distinction is important: a derogation is not equivalent to the permanent opt-out granted to Denmark.

17.2 ERM II

The Exchange Rate Mechanism II (ERM II) is the framework through which non-euro Member States demonstrate exchange-rate stability before adopting the euro.

Participation requires the national currency to remain within the agreed exchange-rate arrangement against the euro for at least two years without severe tensions, particularly without unilateral devaluation against the euro.

ERM II is an important element of the convergence process because it demonstrates that a country can maintain exchange-rate stability before entering monetary union.

18. The Convergence Criteria and Adoption of the Euro

Article 140 TFEU establishes the procedure for assessing whether a Member State with a derogation is ready to adopt the euro.

The assessment is based on the convergence criteria, commonly known as the Maastricht criteria.

These criteria seek to ensure that a Member State has achieved sufficient economic and legal convergence to participate in monetary union.

18.1 Price stability

The inflation rate must be sufficiently close to that of the best-performing Member States in terms of price stability.

The reference is based on the average inflation rate of the three best-performing Member States, with a permitted margin of 1.5 percentage points.

The objective is to ensure that the candidate country has achieved sustainable price stability rather than temporary inflation convergence.

18.2 Sound public finances

The Member State must not be subject to a Council decision establishing the existence of an excessive deficit under Article 126 TFEU.

The assessment takes account of the relevant deficit and debt reference values, together with the circumstances recognised by the Treaty and applicable legislation.

18.3 Exchange-rate stability

The Member State must have participated in ERM II for at least two years without severe tensions and without unilateral devaluation against the euro.

This criterion assesses whether the national currency can remain stable within the exchange-rate framework.

18.4 Convergence of long-term interest rates

The long-term nominal interest rate must not exceed the reference value calculated by comparison with the three best-performing Member States in terms of price stability, plus two percentage points.

The criterion is intended to assess whether convergence is durable and supported by stable economic conditions.

18.5 Legal convergence

Economic indicators alone are insufficient.

The candidate country’s national legislation must also be compatible with the Treaties and the Statute of the ESCB and ECB.

In particular, national central bank legislation must provide for the necessary independence, objectives and institutional integration.

The Commission and ECB assess these conditions through convergence reports, which must be prepared at least once every two years or at the request of a Member State seeking to adopt the euro.

The Council ultimately decides whether the Member State fulfils the necessary conditions, following the procedure established by Article 140.

19. Bulgaria and the Expansion of the Euro Area

Bulgaria provides an important contemporary example of the legal and institutional process of monetary integration.

After years of preparation and participation in ERM II from July 2020, Bulgaria completed the necessary convergence process and adopted the euro on 1 January 2026.

Its accession illustrates the practical application of Article 140 TFEU, the convergence criteria and the legal requirements governing participation in the Eurosystem.

The transition required more than the replacement of banknotes and coins. It involved legal alignment, central bank integration, the irrevocable fixing of the conversion rate and the introduction of the euro as the national currency.

Following adoption, the Bulgarian National Bank became part of the Eurosystem and participates in the common monetary policy framework.

Bulgaria’s accession also demonstrates that monetary union remains an evolving project. The euro area is not a closed group defined permanently by its original membership. It can expand as additional Member States satisfy the Treaty requirements.

20. Democratic Accountability and Judicial Control

The institutional independence of the ECB does not place monetary policy outside the rule of law.

The ECB is subject to the Treaties and its actions may be reviewed by the Court of Justice under the applicable provisions.

Article 263 TFEU provides for judicial review of acts intended to produce legal effects, subject to the standing and admissibility requirements.

Article 267 allows national courts to refer questions concerning the interpretation or validity of EU law to the Court of Justice.

The ECB is also accountable through institutional reporting and parliamentary scrutiny.

Under Article 284 TFEU, the ECB President and other Executive Board members may appear before the competent committees of the European Parliament.

The ECB publishes reports and communicates its decisions and monetary policy assessments.

The European Parliament does not direct the ECB’s monetary policy, because that would undermine the independence guaranteed by Article 130 TFEU. Nevertheless, democratic scrutiny remains an important component of the institutional balance.

The Court of Justice has also clarified the constitutional limits of monetary policy.

In Gauweiler, Case C-62/14, the Court examined the ECB’s Outright Monetary Transactions programme and considered its compatibility with the Treaties.

In Weiss, Case C-493/17, it examined the ECB’s public sector asset purchase programme.

These judgments demonstrate that monetary policy measures must be assessed in the light of the ECB’s mandate, the principle of proportionality and the division of competences established by the Treaties.

21. The Constitutional Limits and Structural Challenges of EMU

EMU has created a highly integrated monetary system, but its institutional structure continues to raise important legal and economic questions.

The most significant structural characteristic is the asymmetry between centralised monetary policy and decentralised fiscal authority.

The ECB determines monetary policy for the euro area as a whole, but national governments retain responsibility for taxation, public expenditure, borrowing and many structural economic decisions.

This creates a need for coordination because national fiscal decisions can affect inflation, borrowing costs, financial stability and the economic conditions of other Member States.

A further challenge concerns the different economic structures of participating countries. A single monetary policy must operate across economies that may differ in productivity, industrial composition, labour-market conditions, public debt and exposure to external shocks.

The loss of independent national exchange-rate policy also changes the mechanisms available for economic adjustment. Member States cannot devalue a national currency against other euro-area currencies to respond independently to economic difficulties.

Instead, adjustment may require changes in productivity, wages, employment, public expenditure, taxation and structural reforms.

The financial and sovereign debt crises revealed weaknesses in the original institutional architecture and led to the development of additional governance and crisis-management mechanisms.

The Banking Union, the European Stability Mechanism, the European Semester and the reformed fiscal framework all reflect attempts to strengthen the resilience of monetary union.

Nevertheless, EMU remains different from a complete fiscal union. It does not possess a single central government budget with the same revenue-raising and expenditure powers as a national state.

The continuing debate about deeper fiscal integration, common borrowing, investment capacity and democratic accountability therefore concerns the future development of the Union rather than the description of a fully established fiscal union.

22. Practical Examples

Example 1: A change in ECB interest rates

The ECB decides to increase its key interest rates in response to inflationary pressures.

Commercial banks across the euro area may adjust their lending and deposit rates. Borrowing costs for households and businesses may increase, affecting consumption, investment and economic activity.

The decision is taken centrally, but its effects differ between Member States because their banking systems, household debt levels and economic structures are not identical.

Example 2: A Member State exceeds the deficit reference value

A Member State records a government deficit above 3% of GDP.

The Commission examines the fiscal situation under Article 126 TFEU and the applicable fiscal framework.

If the relevant conditions are satisfied, an excessive deficit procedure may be initiated. The Council may issue recommendations and require corrective measures.

The existence of a deficit above the reference value does not, by itself, mean that a financial sanction is automatically imposed.

Example 3: A country seeks to adopt the euro

A Member State with a derogation wishes to adopt the euro.

It must satisfy the convergence criteria, participate in ERM II for the required period and ensure that its national legislation is compatible with the relevant EU monetary law.

The Commission and ECB assess the country’s progress through convergence reports.

The Council then determines whether the conditions for adoption have been fulfilled.

Example 4: Financial assistance to a euro-area Member State

A euro-area country experiences severe financing difficulties and requests assistance.

The European Stability Mechanism may provide financial support subject to the applicable legal framework and conditions.

The assistance does not automatically transfer the beneficiary state’s existing financial obligations to other Member States. Article 125 TFEU and the reasoning in Pringle remain relevant to the legal assessment.

Example 5: A national government attempts to obtain direct central bank financing

A national government seeks a direct loan from its national central bank to finance public expenditure.

Article 123 TFEU prohibits the relevant credit arrangement.

The national government must instead obtain financing through lawful budgetary and market mechanisms.

23. Key Takeaways

1. Economic and Monetary Union combines coordination of national economic policies with a single monetary policy for participating Member States.
2. The principal legal foundations of EMU are contained in Articles 119–144 TFEU and the relevant protocols.
3. The Maastricht Treaty established the legal and institutional foundations of the single currency.
4. EMU developed through three stages, culminating in the introduction of the euro in 1999 and the circulation of euro banknotes and coins in 2002.
5. The European System of Central Banks includes the ECB and all EU national central banks, while the Eurosystem consists of the ECB and the central banks of euro-area countries.
6. The ECB’s primary objective is price stability, and its independence is protected by Article 130 TFEU.
7. Economic policy remains substantially national, but Member States must coordinate their policies and comply with EU economic governance rules.
8. The Stability and Growth Pact provides preventive and corrective mechanisms for fiscal surveillance, based on the Treaty reference values of 3% of GDP for deficits and 60% for government debt.
9. The 2024 reform introduced national medium-term fiscal-structural plans and country-specific net expenditure paths.
10. The European Semester coordinates economic, fiscal, employment and structural policies across the Union.
11. The Macroeconomic Imbalance Procedure identifies economic risks beyond public deficits and debt.
12. Article 123 TFEU prohibits monetary financing of public authorities, while Article 125 establishes the no-bailout principle.
13. The Banking Union and European Stability Mechanism strengthen financial stability and crisis management.
14. Most EU Member States are expected to adopt the euro when they fulfil the convergence criteria, while Denmark has a Treaty-based opt-out.
15. Bulgaria adopted the euro on 1 January 2026, becoming the twenty-first euro-area Member State.

24. Frequently Asked Questions

What is Economic and Monetary Union?

Economic and Monetary Union is the framework through which EU Member States coordinate their economic policies and, for countries adopting the euro, participate in a single monetary system with a common currency and monetary policy.

Do all EU Member States use the euro?

No. As of November 2026, twenty-one EU Member States use the euro. Denmark has a Treaty-based opt-out, while other non-euro Member States have not yet completed the process of adopting the currency.

What is the difference between the ESCB and the Eurosystem?

The European System of Central Banks consists of the ECB and the national central banks of all EU Member States. The Eurosystem consists of the ECB and the national central banks of euro-area countries. The Eurosystem conducts the single monetary policy.

What is the primary objective of the ECB?

Under Article 127 TFEU, the primary objective of the ESCB is to maintain price stability. The ECB currently interprets this through a symmetric two per cent inflation target over the medium term.

What are the Maastricht convergence criteria?

They are the economic and legal requirements that a Member State must satisfy before adopting the euro. They concern price stability, public finances, exchange-rate stability, long-term interest-rate convergence and compatibility of national legislation with EU monetary law.

What is the Stability and Growth Pact?

It is the EU framework for monitoring and coordinating national fiscal policies. It aims to maintain sound public finances and prevent excessive deficits and unsustainable debt.

Does the 3% deficit rule mean that every higher deficit is automatically unlawful?

No. The 3% reference value is part of the Treaty framework, but the excessive deficit procedure requires an assessment under Article 126 TFEU and the applicable legislation. Relevant economic circumstances and other legal conditions must be considered.

What is the European Semester?

It is the annual framework for coordinating and monitoring Member States’ economic, fiscal, employment and structural policies. It includes assessments, national plans and country-specific recommendations.

What is the no-bailout clause?

Article 125 TFEU prevents the Union and Member States from assuming the financial commitments of another Member State’s public authorities. It does not prohibit all forms of conditional financial assistance, as clarified by the Court of Justice in Pringle.

Can the ECB finance national government spending directly?

No. Article 123 TFEU prohibits direct monetary financing of public authorities by the ECB and national central banks, subject to the specific scope of the Treaty provision.

What is the European Stability Mechanism?

The ESM is an intergovernmental financial assistance mechanism established by euro-area Member States. It provides conditional financial support to participating countries experiencing or threatened by serious financing difficulties.

Why is monetary union not a complete fiscal union?

Because the euro area has a common monetary policy but does not have a single central fiscal authority with comprehensive powers over taxation, public expenditure and national budgets. Those responsibilities remain primarily national, subject to EU coordination and fiscal rules.

25. Conclusion

Economic and Monetary Union is one of the most advanced forms of economic integration developed within the European Union. It combines a common currency, centralised monetary authority and an extensive system of economic and fiscal coordination.

Its constitutional structure reflects a deliberate division of responsibilities. The ECB conducts the single monetary policy for the euro area and operates independently within the limits of its Treaty mandate. National governments retain substantial authority over taxation, public expenditure and economic policy, but their decisions are subject to common rules, surveillance and coordination mechanisms.

The development of EMU has also demonstrated that monetary integration requires institutions capable of addressing financial instability, fiscal risks and economic imbalances. The Stability and Growth Pact, the European Semester, the Macroeconomic Imbalance Procedure, the Banking Union and the European Stability Mechanism are all elements of this evolving framework.

Nevertheless, EMU remains an incomplete form of economic integration. The euro area has a common currency but not a fully centralised fiscal government. Its long-term stability depends on the relationship between national economic responsibility, collective coordination, financial solidarity and the independence of monetary institutions.

The adoption of the euro by additional Member States, including Bulgaria in 2026, demonstrates that the project remains open to further development. Its future evolution will continue to depend on the legal balance between national sovereignty and common European economic governance.

Ultimately, EMU is not simply a currency arrangement. It is a constitutional and institutional system through which the Union seeks to reconcile monetary stability, economic interdependence, national budgetary responsibility and the broader objectives of European integration.

26. Primary Legal Sources and Further Reading

Treaty provisions

• Article 119 TFEU – Economic and Monetary Union
• Article 121 TFEU – Coordination of Economic Policies
• Article 123 TFEU – Prohibition of Monetary Financing
• Article 125 TFEU – Financial Responsibility of Member States
• Article 126 TFEU – Excessive Deficit Procedure
• Article 127 TFEU – Objectives and Tasks of the ESCB
• Article 130 TFEU – Independence of the ECB
• Article 140 TFEU – Convergence and Adoption of the Euro

EU legislation and protocols

• Protocol No 4 – Statute of the European System of Central Banks and the European Central Bank
• Protocol No 12 – Excessive Deficit Procedure
• Protocol No 13 – Convergence Criteria
• Protocol No 14 – Eurogroup
• Regulation (EU) 2024/1263 – Economic Policy Coordination and Multilateral Budgetary Surveillance
• Regulation (EU) 2024/1264 – Amendment of the Excessive Deficit Procedure Framework
• Directive (EU) 2024/1265 – National Budgetary Frameworks
• Regulation (EU) No 1176/2011 – Prevention and Correction of Macroeconomic Imbalances

Court of Justice case law

• Pringle v Government of Ireland, Case C-370/12
• Gauweiler and Others, Case C-62/14
• Weiss and Others, Case C-493/17

European Central Bank resources

• Economic and Monetary Union – ECB
• The Eurosystem and the European System of Central Banks
• Monetary Policy – ECB
• The ECB’s Monetary Policy Strategy

European Commission and Council resources

• Economic Governance Framework – European Commission
• Convergence Criteria for Joining the Euro Area
• Convergence Reports
• Economic Governance Framework – Council of the European Union
• Joining the Euro Area – Council of the European Union
• The EU Framework for Fiscal Policies – European Parliament