On 1 February 2003, the Treaty of Nice enters into force. The Treaty makes adaptations to the European institutions, which are necessary for enlargement. The Treaty will also facilitate decision-making in the Council of Ministers by changing the decision rule from unanimity to qualified majority in a number of policy fields. It foresees a major reform of the Union's judicial system in order to tackle the case overload in the Court of Justice. Finally, it improves the procedure to detect and address a serious breach of fundamental rights by a Member State.

President Prodi stated: "The Treaty of Nice makes the necessary changes to prepare the European institutions for enlargement. It paves the way for the first peaceful unification of the European continent. Nice will also allow Europe to act more effectively because it scraps the national veto right in some areas".

The institutional changes foreseen by Nice will take concrete effect in 2004, the year when enlargement will happen. The new European Parliament, which will be elected in June 2004, will have 732 members. This is the new maximum number defined in the Nice Treaty, which also contains a new division of seats per Member State. The next European Commission, which will take office in November 2004, will have 25 members (one per Member State). This means that the bigger Member States will no longer appoint a second Commissioner. Once the EU reaches 27 members, the number of Commissioners will be lower than the number of Member States. Also from 1 November onwards, a new weighting of votes will apply in the Council of Ministers. In addition to meeting the threshold for a qualified majority vote, Nice stipulates that a vote in the Council will need the support of a majority of Member States, and that a Member State can request verification of whether the majority vote represents at least 62% of the population.

The Treaty of Nice will also facilitate decision-making in the Council of Ministers. It contains 27 provisions, which move from the unanimity rule to a vote with qualified majority. For instance, measures to encourage actions that counter discrimination, specific support measures in the industrial policy field, the statute and regulations governing political parties at European level, and judicial cooperation in civil proceedings having cross-border implications all move away from unanimity. These and other cases also become part of the co-decision procedure, which means that the European Parliament will legislate on an equal footing with the Council.

The negotiation and conclusion of international agreements on services and commercial aspects of intellectual property from now on fall under the qualified majority rule, with some exceptions. Finally, the future appointment of key figures, such as the President and Members of the European Commission, the High Representative for the Common Foreign and Security Policy, special representatives, and the deputy Secretary-general of the Council, will no longer require a unanimous decision in the Council.

The President of the European Commission receives increased powers. He or she can decide on the internal organisation of the Commission; will allocate portfolios to Commissioners and if necessary reassign them during the term of office; will appoint a number of vice-presidents, after collective approval of the College; and may request a Commissioner to resign subject to approval by the College.

The Nice Treaty introduces a new procedure to detect a potential serious breach of fundamental rights by a Member State. If this new prevention mechanism failed to address the situation, the European Council could declare the actual existence of such a breach and suspend certain rights of the country concerned, for instance the right to vote in the Council.

The Nice Treaty allows for a major reform of the Union's judicial system in order to tackle the problem of case overload and speed up the delivery of judgements. It provides for the possibility of setting up internal chambers in the Court of First Instance to deal with certain proceedings. The possibility for more decentralisation in the handling of cases within the Court of Justice is foreseen. The approval by the Council of the rules of procedures of both Courts will happen by qualified majority instead of unanimity. In foreseeing this reform, the Nice Treaty ensures the coherence of jurisprudence.

Commissioner Barnier, who was negotiator for the European Commission of the Nice Treaty, declared : "Our immediate challenge is to manage the first stage of enlargement, for which the Treaty of Nice is indispensable. But the Treaty does not give fully adequate solutions to make an enlarged Union work effectively. The Convention on the Future of the Union should help the next Intergovernmental Conference to find the political will, which was sometimes lacking during the Nice negotiations".