It was approved by referendum on 10 May 1972, and signed into law by the President of Ireland Éamon de Valera on 8 June of the same year.

Belgium, France, West Germany, Italy, Luxembourg and the Netherlands formed the European Coal and Steel Community in 1951.

A second application was made in 1967, and in 1972, the six member states signed a Treaty of Accession with Denmark, Ireland, Norway and the United Kingdom.

[citation needed] Then President Éamon de Valera privately opposed the state's entry and voted 'no', citing the loss of sovereignty.

[8] Official Sinn Féin (now the Workers Party) opposed the state's entry, citing anti-imperialism and calling the EC a "rich man's club".

On 1 January 1973, Ireland, Denmark and the United Kingdom became member states of the European Communities (Norway had rejected membership in a referendum).

in particular, the Twenty-eighth Amendment of the Constitution of Ireland approved in 2009, allowing the ratification of the Treaty of Lisbon, created a different structure to the subsections in Article 29.4.