European Atomic Energy Community in the context of Nuclear power

The European Economic Community (EEC) was a regional organisation created by the Treaty of Rome of 1957, aiming to foster economic integration among its member states. It was subsequently renamed the European Community (EC) upon becoming integrated into the first pillar of the newly formed European Union (EU) in 1993. In the popular language, the singular European Community was sometimes inaccurately used in the wider sense of the plural European Communities, in spite of the latter designation covering all the three constituent entities of the first pillar. The EEC was also known as the European Common Market (ECM) in the English-speaking countries, and sometimes referred to as the European Community even before it was officially renamed as such in 1993. In 2009, the EC formally ceased to exist and its institutions were directly absorbed by the EU. This made the Union the formal successor institution of the Community.

The Community's initial aim was to bring about economic integration, including a common market and customs union, among its six founding members: Belgium, France, Italy, Luxembourg, the Netherlands and West Germany. It gained a common set of institutions along with the European Coal and Steel Community (ECSC) and the European Atomic Energy Community (EURATOM) as one of the European Communities under the 1965 Merger Treaty (Treaty of Brussels). In 1993, a complete single market was achieved, known as the internal market, which allowed for the free movement of goods, capital, services, and people within the EEC. In 1994 the internal market was formalised by the EEA agreement. This agreement also extended the internal market to include most of the member states of the European Free Trade Association, forming the European Economic Area, which encompasses 15 countries.

The Euratom Treaty, officially the Treaty establishing the European Atomic Energy Community, established the European Atomic Energy Community. It was signed on 25 March 1957 at the same time as the Treaty establishing the European Economic Community (EEC Treaty).

The Euratom Treaty is less well known because of the lower profile of the organisation that it founded. The EEC has evolved into what is now the European Union, but Euratom has remained much the same as it was in 1957 although it is governed by the institutions of the European Union. It was established with its own Commission and Council, but the 1967 Merger Treaty merged these institutions of Euratom and the European Coal and Steel Community with those of the EEC.

The European Communities (EC) were three international organizations that were governed by the same set of institutions. These were the European Coal and Steel Community (ECSC), the European Atomic Energy Community (EAEC or Euratom), and the European Economic Community (EEC), the last of which was renamed the European Community (EC) in 1993 by the Maastricht Treaty establishing the European Union. The European Union was established at that time more as a concept rather than an entity, while the Communities remained the actual subjects of international law impersonating the rather abstract Union, becoming at the same time its first pillar. In popular language, however, the singular European Community was sometimes used interchangeably with the plural phrase, in the sense of referring to all three entities.

The European Coal and Steel Community ceased to exist in 2002 when its founding treaty expired. The European Community was merged with the second and third EU pillars by the Treaty of Lisbon in 2009, finally allowing the European Union to move beyond being only a concept and to assume the shape of a legally incorporated international organization with juridical personality, designated as the legal successor to the Community. However, the reformed EU has not become entirely unified, because Euratom, though governed with the EU by the common set of institutions, has been retained as an entity distinct from the EU, along with a number of other international entities, such as the European Investment Bank, the European University Institute, the European Stability Mechanism, and the Unified Patent Court.

Between 1993 and 2009, the European Union (EU) legally comprised three pillars. This structure was introduced with the Maastricht Treaty on 1 November 1993, and was eventually abandoned on 1 December 2009 upon the entry into force of the Treaty of Lisbon, when the EU obtained a consolidated legal personality.

1. The European Communities pillar handled economic, social and environmental policies. It comprised the European Community (EC), the European Coal and Steel Community (ECSC, until its expiry in 2002), and the European Atomic Energy Community (EURATOM).
2. The Common Foreign and Security Policy (CFSP) pillar took care of foreign policy and military matters.
3. Police and Judicial Co-operation in Criminal Matters (PJCCM) brought together co-operation in the fight against crime. This pillar was originally named Justice and Home Affairs (JHA)

The Merger Treaty, also known as the Treaty of Brussels, was a European treaty which unified the executive institutions of the European Coal and Steel Community (ECSC), European Atomic Energy Community (Euratom) and the European Economic Community (EEC). The treaty was signed in Brussels on 8 April 1965 and came into force on 1 July 1967. It set out that the Commission of the European Communities should replace the High Authority of the ECSC, the Commission of the EEC and the Commission of Euratom, and that the Council of the European Communities should replace the Special Council of Ministers of the ECSC, the Council of the EEC and the Council of Euratom. Although each Community remained legally independent, they shared common institutions (prior to this treaty, they already shared a Parliamentary Assembly and Court of Justice) and were together known as the European Communities. This treaty is regarded by some as the real beginning of the modern European Union.

This treaty was abrogated by the Amsterdam Treaty signed in 1997:

The European Union–Ukraine Association Agreement is a European Union Association Agreement between the European Union (EU), the European Atomic Energy Community (Euratom), Ukraine and the EU's 28 member states at the time (which are separate parties in addition to the EU and Euratom). It establishes a political and economic association between the parties. The agreement entered into force on 1 September 2017; previously parts had been provisionally applied. The parties committed to co-operate and converge economic policy, legislation, as well as regulation across a broad range of areas, including equal rights for workers, steps towards visa-free movement of people, the exchange of information and staff in the area of justice, the modernisation of Ukraine's energy infrastructure and access to the European Investment Bank (EIB). The parties committed to regular summit meetings and meetings among ministers, other officials and experts. The agreement furthermore establishes a Deep and Comprehensive Free Trade Area between the parties.

The agreement commits Ukraine to economic, judicial and financial reforms to converge its policies and legislation to those of the European Union. Ukraine commits to gradually conform to EU technical and consumer standards. The EU agrees to provide Ukraine with political and financial support, access to research and knowledge, and preferential access to EU markets. The agreement commits both parties to promote a gradual convergence toward the EU's Common Security and Defence Policy and European Defence Agency policies.

The European Communities Act 1972 (c. 68), also known as the ECA 1972, was an act of the Parliament of the United Kingdom which made legal provision for the accession of the United Kingdom as a member state to the three European Communities (EC) – the European Economic Community (EEC, the 'Common Market'), European Atomic Energy Community (Euratom), and the European Coal and Steel Community (ECSC, which became defunct in 2002); the EEC and ECSC subsequently became the European Union.

The Act also incorporated Community Law (later European Union Law), along with its acquis communautaire, its treaties, regulations, directives, decisions, the Community Customs Union (later European Union Customs Union), the Common Agricultural Policy (CAP), the Common Fisheries Policy (FCP) together with judgments of the European Court of Justice into the domestic law of the United Kingdom.

The EU–UK Trade and Cooperation Agreement (TCA) is a free trade agreement signed on 30 December 2020, between the European Union (EU), the European Atomic Energy Community (Euratom), and the United Kingdom (UK). It provisionally applied from 1 January 2021, when the Brexit transition period ended, before formally entering into force on 1 May 2021, after the ratification processes on both sides were completed: the UK Parliament ratified on 30 December 2020; the European Parliament and the Council of the European Union ratified in late April 2021.

The agreement, which governs the relationship between the EU and the UK after Brexit, was concluded after eight months of negotiations. It provides for free trade in goods and limited mutual market access in services, as well as for cooperation mechanisms in a range of policy areas, transitional provisions about EU access to UK fisheries, and UK participation in some EU programmes. Compared to the UK's previous status as an EU member state, on 1 January 2021 the following ended as they are not incorporated in the TCA or the Brexit withdrawal agreement: free movement of persons between the parties; UK membership in the European Single Market and Customs Union; UK participation in most EU programmes; part of EU–UK law enforcement and security cooperation such as the access to real time crime data; defense and foreign policy cooperation; and the authority of the European Court of Justice in dispute settlement (except with respect to the Northern Ireland Protocol).

The European Union is a geo-political entity, created in 1993, covering a large portion of the European continent. It is founded upon numerous treaties and has undergone expansions and secessions that have taken it from six member states to 27, a majority of the states in Europe.

Since the beginning of the institutionalised modern European integration in 1948, the development of the European Union has been based on a supranational foundation that would "make war unthinkable and materially impossible" and reinforce democracy amongst its members as laid out by Robert Schuman and other leaders in the Schuman Declaration (1950) and the Europe Declaration (1951). This principle was at the heart of the European Coal and Steel Community (ECSC) (1951), the Treaty of Paris (1951), and later the Treaty of Rome (1957) which established the European Economic Community (EEC) and the European Atomic Energy Community (EAEC). The Maastricht Treaty (1992) created the European Union with its pillars system, including foreign and home affairs alongside the European Communities. This in turn led to the creation of the single European currency, the euro (launched 1999). The ECSC expired in 2002. The Maastricht Treaty has been amended by the treaties of Amsterdam (1997), Nice (2001) and Lisbon (2007), the latter merging the three pillars into a single legal entity, though the EAEC has maintained a distinct legal identity despite sharing members and institutions.

The accession of the United Kingdom to the European Communities (EC) – the collective term for the European Coal and Steel Community (ECSC), the European Economic Community (EEC) and the European Atomic Energy Community (EAEC) – took effect on 1 January 1973. This followed ratification of the Accession treaty which was signed in Brussels on 22 January 1972 by the Conservative prime minister Edward Heath, who had pursued the UK's application to the EEC since the late 1950s. The ECSC and EEC would later be integrated into the European Union under the Maastricht and Lisbon treaties in the early 1990s and mid-2000s.

The UK had been the first country to establish a Delegation to the ECSC in 1952, and the first country to sign an Association Agreement with the Community in 1954. The UK had first applied to join in 1961, but this was vetoed by French President Charles de Gaulle. A second application, in 1967, was again vetoed by France. After de Gaulle had relinquished the French presidency in 1969, the UK made a third and successful application for membership. Denmark and Ireland also joined as part of the same expansion.