The European Communities (Amendment) Act 1986 was passed to allow provisions of the SEA to become part of domestic Irish law.

On 22 December 1986, Raymond Crotty sought an injunction preventing Minister for Foreign Affairs Peter Barry from ratifying the Treaty on behalf of the state.

In a majority judgment delivered in Crotty v. An Taoiseach, the Court held that Title III of the SEA would bind the State to concede part of its sovereignty in a manner not permitted by the Constitution under the amendment made in 1972 to allow accession to the European Communities.

[3] It passed Final Stages in the Dáil on 24 April by 123 votes to 17, on this occasion with the Progressive Democrats supporting its passage.

Because of the decision of the Supreme Court in Crotty v An Taoiseach, the constitution would need to be amended on every further occasion before a treaty could be ratified that would transfer sovereignty from the Irish government to a supranational authority.