The Origins of European Integration: From Post-War Reconstruction to the European Union

The Origins of European Integration: From Post-War Reconstruction to the European Union

Introduction

The European Union is one of the most ambitious political, economic and legal experiments in modern history. Its creation was neither the result of a single treaty nor the fulfilment of a predetermined political plan. It emerged through a gradual process of cooperation between European states that had experienced the devastating consequences of two world wars, the collapse of established political structures and the profound economic and social instability of the first half of the twentieth century.

The origins of European integration lie in a fundamental historical question: how could European countries prevent another catastrophic conflict while rebuilding their economies, restoring political stability and preserving their national identities? The answer gradually developed through economic cooperation, shared institutions, common legal commitments and the progressive transfer of certain governmental responsibilities to European institutions.

What began as an initiative to place strategic industrial production under common supervision eventually developed into a complex legal and political union exercising authority over trade, competition, agriculture, environmental protection, consumer rights, monetary policy, migration, fundamental rights and numerous other areas of public life.

The European Union did not emerge from the traditional process of creating an international organisation whose principal purpose was to coordinate the activities of sovereign governments. Its development produced something considerably more sophisticated: a legal order in which common rules could create rights for individuals, impose obligations on businesses, bind national authorities and, under established conditions, prevail over conflicting national law.

Understanding this transformation requires examining the historical circumstances that gave birth to European cooperation, the political ideas that inspired its founders, the institutional experiments that followed the Second World War and the successive legal developments that eventually produced the modern European Union.

The history of European integration is therefore not simply a history of treaties. It is also a history of changing conceptions of sovereignty, constitutional authority, economic interdependence, democratic governance and the relationship between national states and supranational institutions.

1. Europe Before Integration: Historical Divisions and the Origins of the European Idea

The idea of a politically united Europe did not originate after the Second World War. Intellectuals, philosophers, political leaders and reformers had proposed various forms of European cooperation for centuries. Their projects differed considerably in purpose and institutional design, but many were motivated by a recurring concern: the political fragmentation of Europe had repeatedly produced rivalry, military confrontation and instability.

During the seventeenth and eighteenth centuries, proposals for European peace frequently centred on the establishment of permanent mechanisms for resolving disputes between sovereign states. The French thinker Charles-Irénée Castel, known as the Abbé de Saint-Pierre, published his Project for Perpetual Peace in the early eighteenth century. Immanuel Kant later developed a philosophical argument for a federation of free states in his 1795 essay Perpetual Peace: A Philosophical Sketch.

These proposals did not envisage the European Union as it exists today. They were primarily concerned with international peace, diplomatic cooperation and the creation of legal mechanisms capable of restraining war between independent political communities.

During the nineteenth century, European integration remained largely an intellectual and political aspiration. The emergence of nation-states, industrialisation, colonial competition and increasingly powerful nationalist movements reinforced the traditional European system of sovereign states. Although international cooperation developed in certain technical and economic fields, particularly transport, communications and trade, no permanent political structure capable of integrating European states emerged.

The First World War profoundly changed this situation. Between 1914 and 1918, European countries experienced unprecedented destruction, economic dislocation and political upheaval. The collapse of several empires transformed the continent’s political geography, while the Treaty of Versailles and the subsequent international settlement attempted to establish a new system of international security.

The creation of the League of Nations in 1919 represented an important attempt to institutionalise international cooperation. However, its inability to prevent renewed aggression exposed the limitations of collective security arrangements that depended heavily on the willingness of sovereign states to cooperate.

The interwar period also produced more concrete proposals for European political integration. In 1929, French Foreign Minister Aristide Briand proposed a system of European federal cooperation within the framework of the League of Nations. His proposal, commonly associated with the idea of a European federal union, sought to establish closer political and economic relations between European states without immediately eliminating their national sovereignty.

The initiative did not produce a lasting institutional structure. The Great Depression, the rise of authoritarian movements, aggressive nationalism and the deterioration of international relations undermined the possibility of meaningful integration.

The Second World War demonstrated the catastrophic consequences of these unresolved divisions. Between 1939 and 1945, Europe experienced military occupation, mass displacement, systematic persecution, genocide, widespread destruction of infrastructure and the collapse of political and economic systems across much of the continent.

The devastation of the war created a new political environment. European leaders increasingly recognised that the restoration of the pre-war balance of power would not provide a sufficient guarantee of lasting peace. A more durable arrangement was required, one that would make renewed military confrontation materially more difficult and politically less attractive.

This historical experience became the essential starting point of European integration.

2. Post-War Reconstruction and the Political Conditions for European Cooperation

In 1945, Europe faced an extraordinary reconstruction challenge. Industrial production had been severely disrupted, transport networks were damaged, cities had been destroyed and millions of people had lost their homes. The economic weakness of European states was accompanied by political uncertainty and growing tensions between the emerging Western and Eastern blocs.

The geopolitical circumstances were particularly important. The United States and the Soviet Union emerged from the war as the dominant global powers, while Europe became one of the principal arenas of the developing Cold War.

Western European governments had to address several interconnected problems:

First, they needed to reconstruct their national economies and restore industrial production. Second, they had to establish a stable political order capable of resisting authoritarianism and extremism. Third, they needed to manage their relations with Germany, whose industrial capacity and geographical position made it impossible to exclude permanently from the European economic and political system.

France, in particular, faced a difficult strategic question. Its post-war security required a framework that could prevent the unilateral re-emergence of German military and industrial power. At the same time, the reconstruction of Western Europe depended on economic recovery, access to industrial resources and the development of stable trading relationships.

The solution increasingly involved institutional cooperation rather than traditional diplomatic agreements alone.

The Marshall Plan and American economic assistance

An important contribution to European reconstruction came from the United States through the European Recovery Program, commonly known as the Marshall Plan.

Announced by US Secretary of State George C. Marshall in June 1947, the programme provided substantial economic assistance to European countries seeking to rebuild their economies. Its objectives included restoring industrial production, stabilising financial systems, improving trade and strengthening economic cooperation.

The Marshall Plan was not an EU initiative and did not create European supranational institutions. Nevertheless, it contributed significantly to the conditions in which European integration could develop.

The distribution and coordination of American assistance required cooperation between participating governments. In 1948, the Organisation for European Economic Co-operation (OEEC) was established to facilitate the administration of recovery assistance and promote economic collaboration.

The OEEC was an important precursor to later European economic cooperation, although it remained an intergovernmental organisation rather than a supranational legal order.

Its institutional experience demonstrated that European governments could coordinate national economic policies and cooperate through permanent international structures without immediately surrendering their sovereignty.

The security dimension of post-war integration

Economic reconstruction was accompanied by the development of collective security arrangements.

In 1948, Belgium, France, Luxembourg, the Netherlands and the United Kingdom signed the Treaty of Brussels, establishing a system of cooperation that included mutual assistance in the event of armed aggression.

The following year, the North Atlantic Treaty was signed in Washington, creating the North Atlantic Treaty Organization (NATO).

These arrangements must be distinguished from the European Communities that emerged during the following decade. NATO was established primarily as a collective defence alliance, while the first European Community would be based on the pooling of specific economic powers under a common institutional framework.

Nevertheless, both developments reflected a broader transformation in European political thinking: national security could no longer be understood exclusively through independent military capabilities and traditional diplomatic alliances.

A stable European order required cooperation extending beyond occasional negotiations between governments.

3. The Congress of Europe and the Movement Towards Political Unity

The post-war period witnessed the emergence of several movements advocating closer European cooperation. Politicians, intellectuals, former resistance members and civil society organisations increasingly argued that European countries should establish permanent institutions capable of overcoming the political fragmentation responsible for repeated conflicts.

One of the most significant developments was the Congress of Europe, held in The Hague in May 1948.

The Congress brought together representatives from different political and intellectual traditions. Among its participants were prominent European figures who supported closer cooperation, although they did not necessarily agree on the institutional form that integration should take.

The central disagreement concerned the relationship between national sovereignty and European political authority.

Some participants favoured a federal Europe, in which Member States would transfer substantial powers to common institutions. Others preferred an intergovernmental model that would preserve national decision-making authority while developing mechanisms for cooperation.

This distinction became one of the defining tensions in European integration and remains relevant to contemporary debates concerning the future of the Union.

The Congress contributed to the establishment of the European Movement, which promoted political integration and encouraged European governments to develop permanent cooperative institutions.

Its influence was particularly important in the field of human rights and institutional cooperation.

In 1949, the Statute of the Council of Europe was signed in London. The Council of Europe subsequently became a separate international organisation dedicated to democracy, human rights and the rule of law.

In 1950, its Member States adopted the European Convention on Human Rights, which entered into force in 1953.

These developments formed part of the wider post-war European reconstruction of democratic institutions. However, the Council of Europe and the European Union followed different institutional paths and must not be treated as interchangeable organisations.

The Council of Europe developed a system of international human rights protection, while European economic integration gradually produced an autonomous legal and political structure with its own institutions and legislative authority.

4. The Schuman Declaration of 9 May 1950: The Beginning of European Integration

The decisive moment in the development of European integration came on 9 May 1950, when French Foreign Minister Robert Schuman presented a proposal that fundamentally changed the direction of post-war European cooperation.

The declaration, commonly known as the Schuman Declaration, proposed placing French and West German coal and steel production under a common authority within an organisation open to other European countries.

The proposal was revolutionary not because it immediately established a European federation, but because it introduced a different method of achieving political reconciliation: the exercise of specific national powers through common supranational institutions.

The political reasoning behind the declaration

The proposal addressed a central problem in Franco-German relations.

Coal and steel were essential resources for industrial reconstruction, but they were also indispensable to the production of military equipment. Control over these industries therefore had both economic and strategic significance.

For France, the future of German industrial development was a fundamental security concern. For West Germany, participation in European economic cooperation offered an opportunity to restore international confidence, rebuild its economy and regain a recognised position within Western Europe.

The Schuman Plan proposed removing these industries from exclusive national control and subjecting their production to common rules.

Its central political proposition was that the countries involved would become economically interdependent in areas that had previously been associated with national rivalry and military competition.

The declaration famously expressed the ambition that war between France and Germany would become not merely unthinkable but materially impossible.

This was an important departure from conventional international diplomacy. Rather than relying exclusively on military alliances, diplomatic guarantees or temporary political agreements, the proposal sought to change the economic and institutional conditions under which states interacted.

Jean Monnet and the method of functional integration

The intellectual and administrative foundations of the Schuman Plan were closely associated with Jean Monnet.

Monnet believed that European political unity could not realistically be achieved through an immediate attempt to create a federal state. National governments were unlikely to surrender extensive sovereign powers through a single constitutional agreement, particularly so soon after the war.

Instead, he advocated a gradual method based on concrete achievements.

Under this approach, governments would begin by integrating specific sectors of economic activity. Shared institutions would manage those sectors, creating practical cooperation and mutual dependence. Successful integration would then make further cooperation politically and economically possible.

This method is frequently associated with functional integration and later became an important influence on the theory of European integration known as neofunctionalism.

The central assumption was that cooperation in one policy area could generate pressure and incentives for cooperation in related areas. Economic integration could therefore create institutional and political consequences extending beyond its original purpose.

For example, a common market in coal and steel required common rules concerning competition, production, prices, investment and access to resources. These requirements created a need for institutions capable of supervising the market and resolving disputes.

The Schuman Declaration therefore contained the beginnings of a much broader institutional project.

The significance of 9 May

The declaration was presented on 9 May 1950. This date is now celebrated annually as Europe Day.

Its importance lies in the fact that it transformed the abstract aspiration of European unity into a concrete legal and institutional proposal.

It established several principles that would influence the development of the European Communities:

• Integration should proceed through practical and measurable achievements.
• Former adversaries should participate in common institutions.
• Certain national powers could be exercised through independent supranational bodies.
• Economic cooperation could serve as an instrument of political reconciliation.
• The process should remain open to additional European states willing to participate.

The declaration did not itself create a legally binding organisation. It provided the political foundation for negotiations that resulted in the Treaty of Paris in 1951.

The distinction between the declaration and the treaty is important: the former was a political proposal, while the latter established an international legal framework creating a new supranational organisation. European Union+2

5. The European Coal and Steel Community: The First Supranational European Organisation

On 18 April 1951, Belgium, France, the Federal Republic of Germany, Italy, Luxembourg and the Netherlands signed the Treaty establishing the European Coal and Steel Community.

The treaty, commonly called the Treaty of Paris, entered into force on 23 July 1952.

The six participating states became known as the founding members of European integration.

Signature of the Paris Treaty creating the ECSC – CECA on April 18, 1951, with Paul van ZEELAND (B), Joseph BECH (L), Joseph MEURICE (B), Carlo SFORZA (I), Robert SCHUMAN (F), Konrad ADENAUER (RFA), Dirk STIKKER (PB), Johannes van den BRINK (NL) – Multimedia Centre

File:European Coal and Steel Community Map 1952.svg – Wikimedia Commons

23 July 1952: European Coal and Steel Community is born | MoneyWeek

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The ECSC represented a fundamental innovation in international institutional law. Its Member States did not simply agree to coordinate their industrial policies through periodic diplomatic meetings. They established a common legal and institutional structure with independent decision-making authority in the defined field of coal and steel.

The objectives of the ECSC

The Community was designed to establish a common market for coal and steel among the participating countries.

Its objectives included:

1. Removing customs duties and quantitative restrictions affecting trade in coal and steel.
2. Eliminating discriminatory practices between producers and consumers.
3. Establishing common rules governing competition and market access.
4. Preventing distortions caused by subsidies and discriminatory national measures.
5. Encouraging industrial modernisation and economic growth.
6. Promoting the gradual improvement of living and working conditions in the relevant industries.

The economic purpose was inseparable from the political objective. By placing strategic industrial resources within a shared institutional framework, the ECSC sought to reduce the possibility that one participating country could independently use these resources to prepare for conflict against another.

The institutional structure of the ECSC

One of the ECSC’s most important contributions to European integration was its institutional design.

The Treaty of Paris established four principal bodies.

The High Authority

The High Authority was the central executive institution of the Community. Its members were appointed independently of national governments and were required to act in the general interest of the Community.

It possessed powers to adopt decisions within the competences conferred by the treaty.

The High Authority is widely regarded as the institutional predecessor of the modern European Commission.

The Special Council of Ministers

The Council represented the governments of the participating states. Its purpose was to ensure that national governmental interests were taken into account in the Community’s decision-making process.

Its participation demonstrated that the ECSC combined supranational authority with intergovernmental representation.

The Common Assembly

The Common Assembly provided a parliamentary and supervisory dimension. Its members were initially appointed by national parliaments rather than directly elected by European citizens.

It possessed certain powers of political supervision, including the ability to censure the High Authority collectively.

Over time, this body developed into the parliamentary institution that ultimately became the European Parliament.

The Court of Justice

The Court of Justice was established to ensure compliance with the treaty and provide judicial control over the actions of Community institutions.

Its existence was particularly important because it meant that the Community’s legal system was not dependent exclusively on political negotiations between governments.

The institutional architecture of the ECSC introduced a model that would influence the later European Communities: an executive authority, a body representing national governments, a parliamentary assembly and a judicial institution.

The ECSC as a new form of international organisation

The significance of the ECSC extended beyond the industries it regulated.

Its institutional structure demonstrated that states could establish a permanent organisation exercising independent powers within a clearly defined legal framework.

This was different from a conventional international organisation in which decisions generally depended on the continuing agreement of national governments.

The ECSC possessed its own legal personality and institutions, while the treaty established a framework under which certain decisions could have binding effects within the participating states.

Nevertheless, the ECSC was not a federal state. The Member States retained their national constitutions, governments, legislatures and extensive sovereign powers.

Its authority was limited to the competences established by the Treaty of Paris.

This combination of limited competences and supranational authority became one of the defining characteristics of European integration.

The limited duration of the ECSC Treaty

An important historical detail is that the Treaty of Paris was concluded for a period of 50 years.

It expired on 23 July 2002.

By that time, the European Economic Community had developed a much broader legal and economic framework. The responsibilities previously exercised under the ECSC Treaty were incorporated into the wider European Community framework, subject to the relevant transitional arrangements.

The expiration of the treaty did not mean that European integration ended. Rather, it marked the conclusion of the first specifically sectoral experiment in supranational integration. European Central Bank+2

6. The Failure of the European Defence Community and the Limits of Early Political Integration

The success of the ECSC encouraged European leaders to consider extending integration into areas traditionally associated with national sovereignty.

One of the most ambitious proposals concerned defence.

The international situation had changed significantly by the early 1950s. The outbreak of the Korean War in 1950 intensified Cold War tensions and increased concerns about Western European security.

The question of German rearmament became particularly controversial.

The United States and other Western governments considered the military participation of West Germany important to European defence. France, however, was reluctant to support the unrestricted re-establishment of German military forces.

In response, French Prime Minister René Pleven proposed the creation of a European Defence Community in October 1950.

The proposal envisaged a common European defence structure in which national military forces would participate within an integrated organisation.

Negotiations resulted in the Treaty establishing the European Defence Community, signed in Paris on 27 May 1952.

The project was accompanied by proposals for a European Political Community, which would have provided a broader political and institutional framework for the defence arrangement.

However, the European Defence Community never entered into force.

On 30 August 1954, the French National Assembly refused to proceed with ratification of the treaty. This effectively ended the project.

The failure demonstrated that European governments were prepared to pool authority in selected economic fields but remained reluctant to transfer comparable powers in matters involving national defence and military sovereignty.

It also revealed the limitations of attempting to accelerate political integration through ambitious institutional designs before sufficient political consensus had developed.

Nevertheless, the failure did not end the European project. It encouraged its supporters to return to the more gradual method that had produced the ECSC.

The lesson was significant: European integration would advance most successfully where common interests could be identified, practical benefits demonstrated and political agreement sustained.

7. The Treaties of Rome: The European Economic Community and Euratom

The next major stage in European integration emerged from the decision to expand cooperation beyond coal and steel.

In June 1955, the foreign ministers of the six ECSC countries met in Messina, Italy, to discuss further integration.

The conference initiated negotiations concerning a broader common market and cooperation in the peaceful use of nuclear energy.

The negotiations were influenced by a report prepared under the leadership of Belgian Foreign Minister Paul-Henri Spaak. The resulting proposals provided the foundation for two new treaties.

On 25 March 1957, the six founding states signed the Treaties of Rome.

These were:

• The Treaty establishing the European Economic Community (EEC).
• The Treaty establishing the European Atomic Energy Community (Euratom).

Both entered into force on 1 January 1958.

Treaty Of Rome

Audiovisual Service – Signature of the Treaties of Rome

Przeczytaj – Traktaty rzymskie. EWG – zpe.gov.pl

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The European Economic Community

The EEC represented a substantial expansion of European integration.

Unlike the ECSC, which concentrated on two specific industrial sectors, the EEC aimed to establish a common market covering a much wider range of economic activities.

The treaty provided for the gradual elimination of customs duties and quantitative restrictions between Member States, the establishment of a common external tariff and the development of common policies in selected areas.

It also established the foundations for the free movement of goods, persons, services and capital.

These four freedoms would eventually become central characteristics of the European internal market.

The EEC was based on the principle that economic integration required more than the removal of border tariffs. National regulations could also create obstacles to cross-border trade and economic activity.

Consequently, the Community required common legislation, coordinated policies and institutions capable of ensuring that Member States complied with their obligations.

The EEC therefore marked the beginning of a much more extensive process of legal integration.

The European Atomic Energy Community

The second treaty established Euratom.

Its purpose was to promote cooperation in the peaceful development and use of nuclear energy.

The participating countries recognised that nuclear energy could become an important source of industrial development and energy security. However, the development of nuclear technology required considerable investment, scientific cooperation, technical standards and safeguards.

Euratom established a legal and institutional framework for cooperation in these fields.

Unlike the ECSC Treaty, which expired in 2002, the Euratom Treaty remains in force.

Although Euratom is closely associated institutionally with the European Union, it retains a distinct treaty framework and legal identity.

The institutional significance of the Treaties of Rome

The Treaties of Rome expanded the institutional system developed under the ECSC.

The EEC and Euratom had their own institutional arrangements, including a Commission, a Council, an Assembly and a Court of Justice within the original framework.

The European Parliamentary Assembly and Court of Justice served the different Communities through common arrangements, while their executive and Council structures were initially distinct.

This arrangement demonstrated the increasing complexity of European integration.

The Member States were no longer participating in a single narrowly defined industrial organisation. They were developing several interconnected Communities with different legal competences and shared institutional elements.

The Treaties of Rome are consequently regarded as among the most important founding instruments of the modern European legal order. europarl.europa.eu+2

8. The Consolidation of the European Communities: Institutional Merger and Early Integration

During the 1960s, the European Communities gradually developed their institutional and economic structures.

Although the ECSC, EEC and Euratom retained separate treaty foundations, their institutional arrangements created administrative complexity.

In 1965, the Member States signed the Treaty establishing a Single Council and a Single Commission of the European Communities, commonly known as the Merger Treaty.

It entered into force on 1 July 1967.

The treaty created a single Commission and a single Council serving all three Communities.

This reform simplified administration and strengthened the institutional coherence of European integration.

However, the three Communities did not merge into a single legal entity. Their separate legal foundations and treaty frameworks continued to exist.

The Luxembourg Compromise

An important political crisis emerged in 1965 when France withdrew its representatives from meetings of the Council of Ministers, a development commonly known as the empty-chair crisis.

The dispute concerned the increasing use of majority voting and the implications of the proposed expansion of Community authority.

France was concerned that decisions affecting vital national interests might be adopted against its wishes.

The crisis was resolved through the Luxembourg Compromise of January 1966.

Although the compromise did not formally amend the treaties, it established a political understanding under which governments could seek continued discussion where a Member State considered that very important national interests were at stake.

This arrangement demonstrated the continuing tension between supranational decision-making and national governmental control.

It also showed that European integration depended not only on legal instruments but on political compromises between Member States.

The completion of the customs union

One of the earliest major economic achievements of the EEC was the completion of its customs union in 1968, ahead of the original transitional timetable.

The customs union abolished customs duties and equivalent charges on trade between Member States and established a common external tariff for goods entering the Community from non-member countries.

This was an important step towards the common market.

However, the existence of a customs union did not automatically eliminate all obstacles to economic integration. Differences in national technical regulations, professional requirements, taxation systems and administrative procedures continued to affect cross-border activity.

Further legal and institutional reforms would therefore be necessary.

9. Enlargement and the Development of the European Communities

The success of the European Communities gradually attracted interest from other European states.

Enlargement became one of the principal mechanisms through which European integration expanded geographically and politically.

It also introduced new legal and institutional challenges, because every new Member State had to accept the obligations arising from the existing treaties and the developing body of Community law.

The first enlargement: 1973

On 1 January 1973, Denmark, Ireland and the United Kingdom joined the European Communities.

The membership increased from six to nine states.

Norway had also signed an accession treaty but did not join following the rejection of membership in a national referendum.

The accession of the United Kingdom was particularly significant because it brought a major European economic and political power into the Communities.

It also introduced a Member State with a different historical approach to European integration, one traditionally more supportive of intergovernmental cooperation and economic liberalisation than extensive supranational political authority.

The southern enlargement: Greece, Spain and Portugal

The next phase was closely connected with the restoration and consolidation of democracy in southern Europe.

Greece joined in 1981, following the end of military rule.

Spain and Portugal joined on 1 January 1986, after their transitions from authoritarian regimes to democratic government.

These accessions demonstrated that European integration was not exclusively an economic project.

Membership increasingly became associated with democratic stability, constitutional government, economic development and the protection of fundamental political values.

The enlargement of 1995

Austria, Finland and Sweden joined the European Union on 1 January 1995.

The accession of these countries brought the membership to fifteen states.

Their participation further strengthened the economic and political importance of the Union and increased the complexity of its institutional decision-making.

The great enlargement of 2004

The collapse of communist regimes in Central and Eastern Europe transformed the political landscape of the continent.

Following the end of the Cold War and the reunification of Germany in 1990, countries previously separated from Western European institutions began pursuing closer political and economic relations with the European Communities.

The largest enlargement took place on 1 May 2004, when ten countries joined:

Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia.

This enlargement was historically significant because it represented a major step towards overcoming the political division of Europe created during the Cold War.

Bulgaria and Romania: The 2007 enlargement

On 1 January 2007, Bulgaria and Romania joined the European Union.

Their accession increased the number of Member States to twenty-seven.

The accession of the two countries followed extensive negotiations concerning the adoption and implementation of the acquis communautaire, institutional reforms, judicial systems, economic regulation and administrative capacity.

For Bulgaria, membership represented a major constitutional and political transformation. European integration became part of the country’s long-term institutional development and international orientation.

Croatia: The 2013 enlargement

Croatia joined the European Union on 1 July 2013, becoming the twenty-eighth Member State at that time.

Its accession demonstrated that enlargement remained an important element of European integration, particularly in relation to the Western Balkans.

Brexit and the first withdrawal from the Union

The United Kingdom, which had joined the European Communities in 1973, held a referendum on EU membership on 23 June 2016.

A majority of participating voters supported leaving the European Union.

The United Kingdom formally notified the European Council of its intention to withdraw under Article 50 TEU on 29 March 2017.

After a prolonged negotiation process, the United Kingdom withdrew from the European Union on 31 January 2020.

The withdrawal demonstrated that EU membership was not legally irreversible and that the treaties contained a mechanism through which a Member State could leave the Union.

Following Brexit, the EU consisted of twenty-seven Member States.

The enlargement process and the withdrawal of the United Kingdom illustrate two different dimensions of European integration: the capacity of the Union to expand through accession and the legal possibility of withdrawal under treaty provisions. European Union+3

10. The Single European Act of 1986: The Road Towards the Internal Market

By the mid-1980s, the European Communities had achieved considerable economic progress. Nevertheless, the common market remained incomplete.

Although customs duties between Member States had largely disappeared, national regulatory differences, administrative restrictions and other non-tariff barriers continued to obstruct cross-border economic activity.

The need for further integration became increasingly apparent.

The Single European Act (SEA), signed in February 1986 and entering into force on 1 July 1987, represented an important institutional and economic reform.

Its central objective was to establish an internal market by the end of 1992.

The internal market was conceived as an area without internal frontiers in which the free movement of goods, persons, services and capital would be ensured.

Legislative and institutional reforms

The Single European Act introduced several important changes.

First, it expanded the use of qualified majority voting in the Council, reducing the possibility that individual Member States could block legislation in areas covered by the new voting arrangements.

Second, it strengthened the legislative role of the European Parliament through the introduction of the cooperation procedure and the assent procedure.

Third, it provided a clearer treaty basis for European political cooperation in foreign policy matters.

Fourth, it introduced or strengthened Community competences in areas such as environmental policy, research and technological development.

The reform was significant because it demonstrated that the development of the common market required institutional changes as well as economic liberalisation.

It also marked a transition towards a more integrated European legal system in which common legislation would increasingly affect domestic regulatory structures.

The Single European Act was therefore an important constitutional and economic milestone preceding the creation of the European Union itself.

11. The Maastricht Treaty: The Establishment of the European Union

The most important constitutional development of European integration before the Treaty of Lisbon was the signing of the Treaty on European Union, commonly known as the Maastricht Treaty.

The treaty was signed on 7 February 1992 and entered into force on 1 November 1993.

It formally established the European Union.

This was a fundamental transformation. Until then, European integration had developed primarily through the European Communities, particularly the European Economic Community. Maastricht created a broader political and legal structure within which economic integration, foreign policy cooperation and cooperation in justice and home affairs could be pursued.

Sommet de Maastricht: 25 ans après, l’UE en proie au doute

How Maastricht changed Europe

HOLLAND-MAASTRICHT-EUROTOP

The three-pillar structure

The original Maastricht framework organised the Union around three pillars.

First pillar: The European Communities

The first pillar included the European Communities, particularly the European Community, Euratom and the ECSC.

It contained the most developed supranational arrangements, including common legislation, judicial enforcement and the institutional mechanisms associated with the Community legal order.

Second pillar: Common Foreign and Security Policy

The second pillar established a framework for cooperation in foreign and security policy.

This area remained primarily intergovernmental, reflecting the sensitivity of foreign affairs and national security.

Third pillar: Justice and Home Affairs

The third pillar initially covered cooperation in areas such as immigration, asylum, judicial cooperation and policing.

Its original institutional design was also predominantly intergovernmental.

The three-pillar structure therefore reflected a compromise between different approaches to European integration.

Some policy areas were governed through supranational institutions, while others remained more directly controlled by national governments.

European citizenship

One of Maastricht’s most important innovations was the introduction of citizenship of the European Union.

EU citizenship was established as a legal status additional to national citizenship.

It introduced a series of rights, including the right to move and reside within the territory of Member States, subject to the conditions established by EU law, as well as political participation rights in European Parliament and municipal elections in the Member State of residence.

It also strengthened the relationship between individuals and the European legal order.

The Union was no longer concerned exclusively with the economic activities of businesses and national governments. Individuals increasingly became direct beneficiaries of rights established by European law.

Economic and Monetary Union

The Maastricht Treaty also established the legal foundations for Economic and Monetary Union.

It provided for a staged process towards the adoption of a single currency and established convergence requirements that participating states would have to satisfy.

The treaty introduced a framework for economic policy coordination and monetary integration, ultimately leading to the introduction of the euro.

The Maastricht reforms therefore extended European integration beyond the traditional common market into monetary and political cooperation.

The significance of Maastricht

Maastricht changed the character of European integration in three fundamental ways.

First, it established the European Union as a broader political structure.

Second, it expanded the rights associated with European citizenship.

Third, it created the legal foundations for the single currency and deeper economic coordination.

However, the European Union created by Maastricht was not yet the unified legal and institutional structure that exists today. The pillar system preserved important distinctions between Community law and intergovernmental cooperation.

Those distinctions would be progressively reduced through subsequent treaty reforms. European Union+1

12. The Amsterdam and Nice Treaties: Preparing the Union for Further Enlargement

Following Maastricht, the European Union faced two interconnected challenges.

It needed to improve its institutional and decision-making arrangements, while preparing for the accession of countries from Central and Eastern Europe.

The Amsterdam and Nice Treaties were important steps in this process.

The Treaty of Amsterdam

The Treaty of Amsterdam was signed on 2 October 1997 and entered into force on 1 May 1999.

It introduced several reforms concerning institutional cooperation, fundamental rights, freedom, security and justice.

One of its principal achievements was the transfer of certain matters previously dealt with under the third pillar into the Community framework.

This included important aspects of immigration, asylum and civil judicial cooperation.

The reform increased the role of supranational decision-making in areas that had traditionally been controlled by national governments.

The treaty also strengthened the Union’s commitment to fundamental rights and established a more developed framework for addressing serious breaches of the principles on which the Union was founded.

Another important development was the incorporation of the Schengen acquis into the EU framework, subject to specific arrangements.

The Schengen system had originally developed through agreements outside the main European Community treaty structure. Its integration into the EU framework strengthened the relationship between border management, free movement and European institutional cooperation.

The Treaty of Nice

The Treaty of Nice was signed on 26 February 2001 and entered into force on 1 February 2003.

Its principal objective was institutional reform in preparation for the major enlargement planned for 2004.

As the number of Member States increased, existing arrangements concerning the composition of institutions, voting rights and decision-making became increasingly difficult to maintain.

The Treaty of Nice therefore modified:

• The composition and functioning of the European Commission.
• The allocation of voting weights within the Council.
• The scope of qualified majority voting.
• The organisation and jurisdiction of the European judicial system.
• The mechanisms for addressing serious breaches of fundamental EU values.

Although Nice did not fundamentally transform the constitutional structure of the Union, it prepared the institutions for a significantly larger membership.

It also demonstrated that institutional enlargement required continuous legal reform.

13. The Constitutional Treaty of 2004: The Attempt to Establish a European Constitution

The development of European integration raised an increasingly important constitutional question: should the Union continue to operate through a collection of interconnected treaties, or should its legal foundations be consolidated into a single constitutional document?

The question became particularly significant following the enlargement process and the growing complexity of the Union’s institutional arrangements.

The European Convention was established in 2002 to examine the future development of the Union and prepare proposals for institutional reform.

It was chaired by former French President Valéry Giscard d’Estaing.

The Convention brought together representatives of national governments, national parliaments, the European Parliament and the European Commission.

Its work resulted in a draft Treaty establishing a Constitution for Europe.

The document sought to consolidate and reorganise the existing treaty framework while introducing further institutional and constitutional reforms.

The proposed constitutional framework

The proposed Constitution contained several important elements:

• A clearer definition of the Union’s competences.
• A more coherent structure of European institutions.
• A strengthened role for the European Parliament.
• A permanent President of the European Council.
• A European Union Minister for Foreign Affairs.
• A more unified system of legislative instruments.
• Formal recognition of the Charter of Fundamental Rights within the constitutional framework.

The proposal also sought to replace several existing treaty instruments with a more consolidated constitutional text.

The Treaty establishing a Constitution for Europe was signed in Rome on 29 October 2004.

However, signature did not mean that the treaty had entered into force.

It required ratification by all Member States in accordance with their respective constitutional requirements.

The French and Dutch referendums

In 2005, the proposed Constitution encountered a major political obstacle.

On 29 May 2005, French voters rejected the treaty in a national referendum.

On 1 June 2005, Dutch voters also rejected it.

These results created a serious ratification crisis.

Although several Member States had already completed their ratification procedures, the treaty could not enter into force without the required ratification by all Member States.

The political reasons for the rejection were varied.

They included concerns about national sovereignty, economic liberalisation, the direction of European integration, democratic accountability and the perceived distance between European institutions and ordinary citizens.

The constitutional project consequently entered a period of uncertainty.

Why the European Constitution never entered into force

The proposed Constitution was never legally established as the constitutional foundation of the European Union.

Its rejection did not mean that European integration stopped or that the existing treaties became invalid.

Instead, European governments sought an alternative method of implementing many of the proposed reforms.

The solution was to negotiate a new amending treaty that would preserve much of the institutional substance of the constitutional project without formally replacing the existing treaty structure with a document entitled a European Constitution.

This process eventually produced the Treaty of Lisbon.

The constitutional debate nevertheless remains important because it exposed the political and legal limits of European integration.

It demonstrated that the development of supranational institutions required not only agreement between governments but also political legitimacy within the Member States.

It also raised a question that continues to influence European constitutional scholarship: how far can a supranational legal order develop constitutional characteristics without becoming a state?

14. The Treaty of Lisbon: The Foundations of the Modern European Union

The Treaty of Lisbon was signed on 13 December 2007 and entered into force on 1 December 2009.

It represents the most important comprehensive reform of the European Union’s institutional and constitutional framework since Maastricht.

Rather than creating a separate European constitutional document, Lisbon amended the existing treaties.

It significantly changed the Treaty on European Union and the Treaty establishing the European Community, which was renamed the Treaty on the Functioning of the European Union.

The two principal treaties, together with the protocols and other instruments forming part of the treaty framework, constitute the foundations of modern EU primary law.

The abolition of the three-pillar structure

One of the most important changes introduced by Lisbon was the abolition of the formal three-pillar structure established by Maastricht.

The Union acquired a more unified institutional and legal framework.

However, this did not mean that all policy areas became subject to identical legal procedures.

The Common Foreign and Security Policy, in particular, retained distinctive institutional and procedural arrangements.

The reform therefore strengthened institutional unity without completely eliminating differences between policy areas.

The legal personality of the European Union

Lisbon expressly established that the European Union possesses legal personality.

Article 47 TEU provides:

“The Union shall have legal personality.”

This provision is fundamental because it confirms the Union’s capacity to act as a legal person in its own right.

It can conclude international agreements within its competences, exercise rights and assume obligations under international law, and participate in international relations through its institutions and authorised representatives.

Before Lisbon, legal personality was expressly attributed to the European Community, while the Union’s own legal personality had been more complicated.

The treaty therefore provided greater clarity concerning the international legal status of the Union.

The European Parliament and democratic representation

The Treaty of Lisbon strengthened the European Parliament’s legislative and budgetary powers.

The ordinary legislative procedure became the principal legislative procedure across a wider range of policy areas.

Under this procedure, the European Parliament and the Council generally act as co-legislators.

This strengthened the democratic dimension of EU decision-making and reduced the number of areas in which Parliament had a merely consultative role.

The President of the European Council

Lisbon created a permanent position of President of the European Council, appointed for a term of two and a half years, renewable once.

Previously, the European Council operated under a rotating presidency arrangement.

The permanent President was intended to provide greater continuity in the political leadership and strategic direction of the Union.

The High Representative for Foreign Affairs and Security Policy

The treaty also established the strengthened position of High Representative of the Union for Foreign Affairs and Security Policy.

The High Representative serves as a principal representative of the Union in foreign and security policy matters and also holds the position of Vice-President of the European Commission.

The arrangement was designed to improve coordination between the Union’s external political activities and its institutional and economic policies.

The Charter of Fundamental Rights

Another major consequence of Lisbon was the recognition of the Charter of Fundamental Rights of the European Union as having the same legal value as the treaties.

The Charter had originally been proclaimed in 2000 but did not initially possess the same binding legal status as the treaties.

Following Lisbon, it became a legally binding instrument within its defined scope of application.

It contains rights and principles concerning dignity, freedoms, equality, solidarity, citizens’ rights and justice.

Its application is subject to Article 51 of the Charter, which determines the circumstances in which EU institutions and Member States are bound by its provisions.

National parliaments and subsidiarity

The Treaty of Lisbon also strengthened the role of national parliaments in monitoring compliance with the principle of subsidiarity.

National parliaments received mechanisms through which they could examine proposed legislative acts and raise objections where they considered that the principle had not been respected.

This reflected an attempt to reconcile supranational decision-making with national democratic accountability.

The citizens’ initiative

Lisbon introduced the European Citizens’ Initiative.

Under this mechanism, citizens can invite the European Commission to consider proposing legislation in an area within its powers, provided the initiative satisfies the applicable legal requirements, including the necessary number of supporting statements from citizens across a sufficient number of Member States.

The initiative does not compel the Commission to introduce legislation, but it creates an additional mechanism for public participation in European policy development.

The constitutional significance of Lisbon

The Treaty of Lisbon did not establish a European Constitution in the formal sense proposed in 2004.

Nevertheless, it preserved and implemented many important elements of the constitutional reform project.

It strengthened the Union’s legal personality, clarified its competences, reinforced the European Parliament, improved institutional continuity and gave binding legal status to the Charter of Fundamental Rights.

It also contributed to the consolidation of the European Union as a distinctive supranational legal order.

The modern Union therefore operates through a treaty-based constitutional framework rather than a single codified national-style constitution. European Union+1

15. From Economic Cooperation to a Supranational Legal and Political Order

The historical development of European integration reveals a gradual but profound transformation.

The original objective was relatively specific: prevent another major conflict in Western Europe by establishing economic cooperation in strategically important industries.

However, the institutional and legal consequences of this cooperation extended far beyond the original objectives.

The ECSC introduced independent supranational institutions. The EEC developed a common market and common policies. The European Communities established an increasingly sophisticated legal system. Maastricht created the European Union, while Lisbon consolidated its modern institutional and constitutional structure.

This development produced a legal order with several distinctive characteristics.

The emergence of an autonomous legal system

One of the most significant developments was the recognition that Community law was not simply another form of international law.

The Court of Justice played a central role in this transformation.

In Van Gend en Loos v Nederlandse Administratie der Belastingen (Case 26/62), the Court recognised that Community law could create rights for individuals that national courts were required to protect.

In Costa v ENEL (Case 6/64), the Court established the principle that Community law could not be overridden by conflicting national law.

These decisions transformed the understanding of European integration.

The Community legal system was no longer concerned exclusively with obligations between governments. It could directly affect the legal position of individuals and businesses.

This development became one of the foundations of the modern European Union.

The transformation of national sovereignty

European integration also changed the traditional understanding of sovereignty.

Member States remain sovereign states with their own constitutions, governments, legislatures and judicial systems.

However, by joining the Union, they accepted treaty obligations and agreed to exercise certain competences through common institutions.

This does not mean that the Union possesses unlimited authority.

The principle of conferral establishes that the Union may act only within the competences attributed to it by the Member States through the treaties.

Nevertheless, within those competences, EU law can have significant effects on national legal systems.

National authorities and courts must therefore operate within a legal environment in which domestic law and European law interact.

The precise constitutional relationship between the two remains an important subject of legal scholarship and judicial interpretation.

The transformation of the European economic model

The European project also developed from a customs union and common market into a more extensive economic framework.

Its activities now include:

• The internal market and its four fundamental freedoms.
• Common competition rules.
• Agricultural and fisheries policies.
• Economic and monetary coordination.
• The euro and the Eurosystem.
• Financial market regulation.
• Environmental and climate legislation.
• Consumer protection.
• Digital markets and data protection.
• Social and employment standards.

The Union’s regulatory activities therefore extend into numerous areas that directly affect the everyday lives of European citizens and the activities of businesses operating across national borders.

The political dimension of integration

European integration has also developed beyond its original economic foundations.

The Union now possesses political institutions with legislative, executive, judicial and supervisory responsibilities.

Its Member States are required to respect common values, including democracy, human dignity, equality, the rule of law and human rights.

The protection of these values has become an important aspect of membership and institutional accountability.

At the same time, the Union remains subject to continuing political debate concerning democratic legitimacy, national sovereignty, institutional transparency and the appropriate limits of supranational authority.

These tensions are not necessarily evidence of institutional failure. They reflect the distinctive nature of a political and legal system that combines national constitutional governments with common supranational institutions.

European integration has therefore remained an evolving constitutional project rather than a completed political arrangement.

16. The Historical Development of European Integration: A Chronological Overview

The following chronology identifies the principal milestones in the transformation of European cooperation into the modern European Union.

Year	Historical development
1945	End of the Second World War in Europe; beginning of reconstruction
1947	Marshall Plan announced
1948	Congress of Europe; Treaty of Brussels
1949	Establishment of the Council of Europe
1950	Schuman Declaration, 9 May
1951	Treaty of Paris signed, establishing the ECSC
1952	ECSC Treaty enters into force
1954	European Defence Community rejected by French National Assembly
1957	Treaties of Rome signed
1958	EEC and Euratom enter into force
1965	Merger Treaty signed
1967	Merger Treaty enters into force
1968	EEC customs union completed
1973	First enlargement: Denmark, Ireland and United Kingdom
1981	Greece joins
1986	Spain and Portugal join; Single European Act signed
1987	Single European Act enters into force
1992	Maastricht Treaty signed
1993	Maastricht Treaty enters into force; European Union established
1995	Austria, Finland and Sweden join
1997	Treaty of Amsterdam signed
1999	Treaty of Amsterdam enters into force
2001	Treaty of Nice signed
2002	ECSC Treaty expires
2003	Treaty of Nice enters into force
2004	Ten countries join; Constitutional Treaty signed
2005	French and Dutch referendums reject the Constitutional Treaty
2007	Bulgaria and Romania join; Treaty of Lisbon signed
2009	Treaty of Lisbon enters into force
2013	Croatia joins
2020	United Kingdom withdraws from the EU

The chronology demonstrates that European integration developed through successive periods of institutional experimentation, economic expansion, political negotiation and constitutional reform.

It was neither linear nor inevitable. Several projects failed, important reforms required prolonged negotiations, and the relationship between national sovereignty and supranational authority repeatedly generated political disagreement.

Yet the overall direction was towards an increasingly integrated legal and institutional system.

17. Key Takeaways

1. European integration developed as a response to the political, economic and social destruction caused by the two world wars.

2. The intellectual foundations of European unity predated the Second World War, but the post-war period created the political conditions necessary for institutional integration.

3. The Schuman Declaration of 9 May 1950 proposed placing French and German coal and steel production under a common supranational authority.

4. The Treaty of Paris, signed in 1951 and effective from 1952, established the European Coal and Steel Community, the first major supranational European organisation.

5. The ECSC introduced an institutional model consisting of an independent High Authority, a Council representing national governments, a Common Assembly and a Court of Justice.

6. The failure of the proposed European Defence Community in 1954 demonstrated the political difficulties associated with transferring powers in sensitive areas of national sovereignty.

7. The Treaties of Rome, signed in 1957 and effective from 1958, established the European Economic Community and Euratom, expanding integration beyond coal and steel.

8. The Merger Treaty of 1965 consolidated the executive and Council structures of the three European Communities without merging their separate legal foundations.

9. The Single European Act of 1986 accelerated the establishment of the internal market and strengthened European legislative procedures.

10. The Maastricht Treaty established the European Union in 1993, introduced EU citizenship and created the foundations for Economic and Monetary Union.

11. The proposed Treaty establishing a Constitution for Europe was signed in 2004 but never entered into force following the rejection of ratification in France and the Netherlands in 2005.

12. The Treaty of Lisbon, effective from 2009, substantially reformed the Union’s institutional structure, confirmed its legal personality and strengthened the legal status of the Charter of Fundamental Rights.

13. European integration developed through successive enlargements, reaching twenty-eight Member States before the United Kingdom’s withdrawal in 2020. The Union currently consists of twenty-seven Member States.

14. The European Union is neither a traditional international organisation nor a federal state. It constitutes a distinctive supranational legal and political order based on treaties concluded by its Member States.

15. The historical development of the Union demonstrates how economic cooperation can generate broader legal, institutional and political integration.

18. Frequently Asked Questions

1. When did the European Union begin?

The European integration process began institutionally with the establishment of the European Coal and Steel Community under the Treaty of Paris, which entered into force on 23 July 1952. The European Union itself was formally established under the Maastricht Treaty, which entered into force on 1 November 1993.

2. Who founded the European Union?

European integration was developed through the collective decisions of six founding states: Belgium, France, the Federal Republic of Germany, Italy, Luxembourg and the Netherlands. Important individuals associated with its origins include Robert Schuman, Jean Monnet, Konrad Adenauer, Alcide De Gasperi and Paul-Henri Spaak.

3. What was the original purpose of European integration?

The original purpose was to establish lasting peace and economic stability in post-war Europe. The first integration project focused on coal and steel production because these industries were essential to both industrial development and military production.

4. What was the Schuman Declaration?

The Schuman Declaration was presented on 9 May 1950 by French Foreign Minister Robert Schuman. It proposed placing French and German coal and steel production under a common authority, with participation open to other European countries. It provided the political foundation for the establishment of the ECSC.

5. What were the three original European Communities?

They were the European Coal and Steel Community (ECSC), the European Economic Community (EEC) and the European Atomic Energy Community (Euratom). They were established through separate treaties and possessed distinct legal foundations.

6. What was the difference between the EEC and the European Union?

The European Economic Community was primarily concerned with economic integration and the establishment of a common market. The European Union, established by the Maastricht Treaty, created a broader political and legal framework encompassing economic integration, citizenship, foreign policy cooperation and justice and home affairs.

7. Why did the European Constitution fail?

The Treaty establishing a Constitution for Europe, signed in 2004, required ratification by every Member State. Its rejection in French and Dutch referendums in 2005 prevented it from entering into force. The subsequent Treaty of Lisbon incorporated many of its proposed institutional reforms through amendments to existing treaties rather than replacing them with a single constitutional document.

8. Does the European Union have a constitution?

The European Union does not have a constitution in the formal sense envisaged by the proposed 2004 Constitutional Treaty. Its constitutional framework is instead based primarily on the Treaty on European Union, the Treaty on the Functioning of the European Union and related legal instruments. These treaties perform many functions associated with constitutional documents, including defining institutions, competences, fundamental values and the exercise of public authority.

9. When did the United Kingdom leave the European Union?

The United Kingdom formally withdrew on 31 January 2020, following the referendum of 23 June 2016 and the subsequent negotiations under Article 50 TEU.

10. How many countries are members of the European Union today?

The European Union has twenty-seven Member States. They include the six founding members and twenty-one countries that joined through successive enlargement processes.

11. Is the Council of Europe part of the European Union?

No. The Council of Europe is a separate international organisation. It is responsible for a broader European system of human rights protection, including the European Convention on Human Rights and the European Court of Human Rights. Neither the Council of Europe nor the European Court of Human Rights is an EU institution.

12. Why is the history of European integration important for understanding EU law?

The historical development of European integration explains the origins of the Union’s institutional structure, legal authority and constitutional principles. Many central doctrines of EU law, including supremacy, direct effect and the allocation of competences, cannot be fully understood without examining the political and legal circumstances in which the European Communities developed.

19. Conclusion

The emergence of the European Union represents a remarkable transformation in the history of European political and legal institutions.

A continent that had repeatedly experienced war, territorial rivalry and political fragmentation gradually developed a system of cooperation based on common legal obligations, shared institutions and the exercise of public authority beyond traditional national boundaries.

The original project was deliberately limited. Rather than attempting to establish a European federation immediately after the Second World War, its founders concentrated on practical economic cooperation in strategically important industries. The European Coal and Steel Community demonstrated that states could entrust common institutions with independent powers while retaining their national political and constitutional identities.

The subsequent establishment of the European Economic Community expanded this approach into a general framework of economic integration. The Maastricht Treaty transformed the Communities into a broader political and legal union, while the Treaty of Lisbon consolidated the institutional arrangements that underpin the modern European Union.

Perhaps the most important lesson of this history is that European integration was not achieved through a single constitutional moment. It developed through successive legal commitments, institutional experiments, political compromises and judicial interpretations.

The European Union consequently occupies a distinctive position within contemporary public international law and constitutional theory. Its legal order is founded on treaties between sovereign states, yet its rules can produce direct legal consequences for individuals, businesses, national authorities and domestic courts.

This combination of national sovereignty, supranational authority and common constitutional principles makes EU law a particularly significant field of legal study.

Understanding its historical origins is therefore essential to understanding its present institutional structure, legislative procedures, judicial doctrines and regulatory activities.

The European Union remains an evolving project. Its future will depend on the continuing relationship between national governments, European institutions and the citizens whose rights and obligations are increasingly shaped by its legal framework.

What began as an effort to make another European war materially more difficult has developed into one of the world’s most extensive systems of regional legal and political integration.

Principal legal and historical sources

The following official sources provide the documentary foundation for this article and are particularly useful for further research.

1. The Schuman Declaration – European Union – The original political proposal and its historical significance.

2. Founding Agreements of the European Union – The principal treaties and their historical development.

3. The Treaty of Rome – European Parliament – The establishment of the EEC and Euratom.

4. How EU Treaties Shaped the Council of the EU and European Council – Institutional and treaty development from Paris to Lisbon.

5. History of EU Enlargement – European Commission – The successive enlargement processes.

6. History of the Court of Justice of the European Union – The development of the European judicial system.

7. EUR-Lex – European Union Law – The official repository of European legislation, treaties and legal documents.

Relevant primary legal instruments:

• Treaty establishing the European Coal and Steel Community (1951).
• Treaty establishing the European Economic Community (1957).
• Treaty establishing the European Atomic Energy Community (1957).
• Treaty establishing a Single Council and a Single Commission of the European Communities (1965).
• Single European Act (1986).
• Treaty on European Union (Maastricht, 1992).
• Treaty of Amsterdam (1997).
• Treaty of Nice (2001).
• Treaty establishing a Constitution for Europe (2004, never entered into force).
• Treaty of Lisbon (2007).