The flags of the 25 Member States of the European Union after the enlargement of May 1st, 2004. (Photo:

In order to join the EU, would-be member states sign an accession treaty with the current member states. Ten countries did so in Athens on 16 April 2003 and became members from 1 May 2004. The accession treaties state that new member states have the same rights and obligations as the existing member states. Some obligations, laid down in special protocols, only enter into force after accession. The accession treaties and acts of accession have to be adopted unanimously by the existing Member States and by every new member state.

There have been referenda in each of the ten new Member States, save Cyprus, to permit national ratification of the accession treaty.

If a country fails to ratify, the numbers of votes and seats, and the figures for qualified majority voting, etc. will be changed proportionally or technically without new negotiations among all Member States. A legal base for such change is inserted in the accession acts.


When an accession treaty is adopted, it is ratified and sent to the Italian Republic, which collects and keeps all instruments of ratification.