how can a state become a member of this?
To become a member, a country must meet the Copenhagen criteria, defined at the 1993 meeting of the European Council in Copenhagen. These require a stable democracy that respects human rights and the rule of law; a functioning market economy; and the acceptance of the obligations of membership, including EU law.
European Union

To become a member, a country must meet the Copenhagen criteria, defined at the 1993 meeting of the European Council in Copenhagen. These require a stable democracy that respects human rights and the rule of law; a functioning market economy; and the acceptance of the obligations of membership, including EU law.
which of the following european nations has opposed the adoption of the euro UNANSWERABLE what is the main identity? The euro (symbol: €; code: EUR) is the official currency of 19 of the member states of the European Union. when was the said union formed? 1999
wiki:1576266
European Union [SEP] Member states
Evaluation of a country's fulfilment of the criteria is the responsibility of the European Council. Article 50 of the Lisbon Treaty provides the basis for a member to leave the Union. Two territories have left the Union: Greenland (an autonomous province of Denmark) withdrew in 1985; the United Kingdom formally invoked Article 50 of the Consolidated Treaty on European Union in 2017, and became the only sovereign state to leave when it withdrew from the EU in 2020. There are six countries that are recognised as candidates for membership: Albania, Iceland, North Macedonia, Montenegro, Serbia, and Turkey, though Iceland suspended negotiations in 2013.