Member states of the European Union in the context of "Primacy of European Union law"

European Union law is a system of supranational laws operating within the 27 member states of the European Union (EU). Originally referred to as Community law, it has grown over time since the 1952 founding of the European Coal and Steel Community, to promote peace, social justice, a social market economy with full employment, and environmental protection. The Treaties of the European Union agreed to by member states form its constitutional structure. EU law is interpreted by, and EU case law is created by, the judicial branch, known collectively as the Court of Justice of the European Union.

Legal Acts of the EU are created by a variety of EU legislative procedures involving the popularly elected European Parliament, the Council of the European Union (which represents member governments), the European Commission (a cabinet which is elected jointly by the Council and Parliament) and sometimes the European Council (composed of heads of state). Only the Commission has the right to propose legislation.

The economic and monetary union (EMU) of the European Union is a group of policies aimed at converging the economies of member states of the European Union at three stages.

There are three stages of the EMU, each of which consists of progressively closer economic integration. Only once a state participates in the third stage it is permitted to adopt the euro as its official currency. As such, the third stage is largely synonymous with the eurozone. The euro convergence criteria are the set of requirements that needs to be fulfilled in order for a country to be approved to participate in the third stage. An important element of this is participation for a minimum of two years in the European Exchange Rate Mechanism ("ERM II"), in which candidate currencies demonstrate economic convergence by maintaining limited deviation from their target rate against the euro.

On 1 January 2007, Bulgaria and Romania became member states of the European Union (EU) in the fifth wave of EU enlargement.

Bulgaria and Romania did not have a referendum related to European Union accession.

The European Atomic Energy Community (EAEC or EURATOM) is an international organization established by the Euratom Treaty of 1957 with the original purpose of creating a specialist market for nuclear power in Europe, by developing nuclear energy and distributing it to its member states while selling the surplus to non-member states. Having become one of the three European Communities alongside the European Coal and Steel Community and the European Economic Community following the merger of their executive bodies in 1967, the Euratom is de facto under the authority of the European Union (EU) but remains de jure a separate organization.

It is legally distinct from the European Union although it has the same membership, and is governed by many of the EU's institutions; but it is the only remaining community organization that is independent of the EU and therefore outside the regulatory control of the European Parliament. Over the years its scope has been increased to cover a variety of areas associated with nuclear power and ionising radiation as diverse as safeguarding of nuclear materials, radiation protection, coordinating EU members' nuclear research programmes for peaceful purposes, and construction of the International Fusion Reactor.

The Western European Union (WEU; French: Union de l'Europe occidentale, UEO; German: Westeuropäische Union, WEU) was the international organisation and military alliance that succeeded the Western Union (WU) after the 1954 amendment of the 1948 Treaty of Brussels. The WEU implemented the Modified Brussels Treaty. During the Cold War, the Western Bloc included the WEU member-states, plus the United States and Canada, as part of the North Atlantic Treaty Organization (NATO).

The Cold War ended c. 1991, and at the turn of the 21st century, WEU tasks and institutions were gradually transferred to the European Union (EU), providing central parts of the EU's new military component, the European Common Security and Defence Policy (CSDP). This process was completed in 2009 when a solidarity clause between the member states of the European Union, which was similar (but not identical) to the WEU's mutual-defence clause, entered into force with the Treaty of Lisbon. The states party to the Modified Treaty of Brussels consequently decided to terminate that treaty on 31 March 2010, with all the WEU's remaining activities to cease within 15 months.On 30 June 2011, the WEU officially ceased to exist; with the European Union taking over its activities.

The European Social Fund Plus (ESF+) is one of the European Structural and Investment Funds (ESIFs), which are dedicated to improving social cohesion and economic well-being across the regions of the Union. The funds are redistributive financial instruments that support cohesion within Europe by concentrating spending on the less-developed regions.

It is the European Union's main financial instrument for supporting employment in the member states of the European Union as well as promoting economic and social cohesion, created by merging the existing European Social Fund with the EU Fund for European Aid to the Most Deprived (FEAD) and the EU Programme for Employment and Social Innovation (EaSI) in 2021. ESF+ spending amounts to around 10% of the EU's total budget. The particular aim of ESF+ spending is to support the creation of more and better jobs in the EU, which it does by co-funding national, regional and local projects that improve the levels of employment, the quality of jobs, and the inclusiveness of the labour market in the member states and their regions.