The 15 member states of the European Union signed at Nice, on 26 February 2001, the Treaty of Nice amending the Treaty on European Union, the Treaties establishing the European Communities and certain related acts. The intergovernmental conference had closed politically on 11 December 2000. The text appeared in Official Journal C 80 of 10 March 2001.

The treaty is drawn up in a single original in twelve equally authentic languages, deposited in the archives of the Italian government, which transmits certified copies to the other parties. Article 12 requires ratification in accordance with national constitutional requirements, with instruments deposited in Rome. It enters into force on the first day of the second month after the last deposit: 1 February 2003. Italy registered it with the United Nations as UNTS I-47937 on 1 October 2010.

The stated purpose was to prepare the institutions for eastward enlargement, after the Treaty of Amsterdam had left voting weights, the size of the Commission and of the Parliament unresolved. This is not an accession handbook. The amendment follows Maastricht and Rome; Lisbon, in 2007, would later replace it as the subsequent architecture.

The Council received a new weighting of votes, with an optional check that the majority represented a sufficient share of the population. The Commission: from 2005, Germany, France, the United Kingdom, Italy and Spain give up their second commissioner; when the Union reaches 27 members, the Council reduces the number below 27, without fixing the figure. The European Parliament would rise, after enlargement, to 732 seats. This is not a voting-tactics table.

The rules on enhanced cooperation, viewed as unworkable after Amsterdam, were rewritten. After the Austrian crisis of 2000, the treaty added a preventive mechanism to Article 7 TEU. Judicial panels were provided for under the Court of Justice and the Court of First Instance. The Charter of Fundamental Rights, proclaimed in 2000, was not incorporated; that was left for the next conference.

In Ireland, the Crotty case-law required a referendum for a transfer of sovereignty. The first vote, in June 2001, rejected the treaty; the second, after the Seville Declaration on neutrality, approved it. The other fourteen states ratified by parliamentary procedure. The last deposit was Irish, hence the application date.

Cover: the Palais des Congrès Acropolis in Nice, the conference venue — the photograph is of the building, not of the signing table. Wikimedia Commons, free licence.

Sources consulted: Treaty of Nice; Treaty of Nice amending the Treaty on European Union.