Abstract: the United Kingdom Labour Party issued Election Manifestos that mandated renegotiation of the terms of Britain's accession treaty with the EEC (1973) and a national referendum to determine Britain's continued membership.The EEC heads of state met in Dublin in March 1975, to conclude the negotiations, after which the British cabinet voted by a majority that the United Kingdom should remain in the EEC.By national referendum of June 5, 1975, a 67.2%British majority voted for the United Kingdom to remain in the EEC. 4 More precisely, Greenland consensually withdrew from the European Communities in 1985, but it was part of Denmark and not a member state by its own right, so it was just a reduction of the territorial scope of the founding Treaties as it meant a partial withdrawal and not a full one.This process was made on the base of an international law instrument, namely the Vienna Convention on the law