Treaty changes

At present, the EU treaties can be amended unanimously by an intergovernmental conference - one member state can therefore block a Treaty change. The final decision must then be sent for ratification by the national parliaments (in some countries by an extended majority) or referenda.

The future

The EU Constitution proposes the "Convention-Method" for treaty amendments. Member States, the EP and the Commission would be able to initiate amendments. Then, the European Council would decide by simple majority if a Convention should be convened. The Convention would decide "by common accord" whether to adopt or not to adopt these amendments. Amendments adopted by the Convention would then have to be ratified by all member states before entering into force.

The adoption of the new EU Constitution, however, would not simply represent a change, but a replacement of the existing treaties. Earlier treaties would be repealed.

In principle, the EU Constitution must be ratified by all member states before it can enter into force.  However, a political declaration attached to the Constitution opens the door for another possibility: if not all, but at least four fifths of the member states ratify the Constitution, the matter shall be referred to the European Council. Member states that would have failed to ratify the Constitution after a period of two years could then be excluded from the Union. This political declaration is also stated in Art. IV-7.4, but will not have legal effect until the Constitution is adopted in all member states.