As the abolition of customs barriers to trade, in 1968, had highlighted the technical and administrative obstacles to intra-Community trade, so the effort to abolish the latter, by 1992, had made clear that the completion of the common market would not bring about a real single market as long as there were still monetary obstacles in the way. Therefore, the integrationists in the original six Member States were, already before the completion of the single market, pushing their new partners to step into the next integration stage, that of the economic and monetary union, and even to sketch the final stage, that of political union. The defenders of the intergovernmental method were, however, reticent. They had joined the Community in order to reap the benefits of the single market and had accepted the cessions of sovereignty necessary to that end. But they were reticent to make any more concessions to the Community method of integration and its evolutionary properties.
The compromise solution found in Maastricht, in December 1991, was to split the integration venture in half. The original European Economic Community Treaty was renamed Treaty on the European Community to signify that it set new objectives over and above the original economic ones, notably for monetary and social integration. The United Kingdom was allowed to opt out of these new goals and the people of Denmark, consulted by referendum, decided not to join the monetary union. A new Treaty on European Union was signed at the same time to outline the objectives of political union, in particular those of a judicial and home affairs policy and those of a common foreign and security policy. But, by common agreement, it was decided that these goals would be pursued by intergovernmental cooperation. Hence, the so-called Treaty of Maastricht, which was signed on 7 February 1992, was in fact made up of two separate but interrelated Treaties: the Treaty on the European Union (TEU); and the Treaty establishing the European Community (TEC). These two Treaties separated the European construction into three pillars or edifices [see section 3.1], distinguished mainly on the basis of the decision-making process: the main pillar or edifice, which is the European Community and where the common work of the participants is regulated by the TEC and where the Community method prevails; the pillar or edifice of justice and home affairs; and the pillar or edifice of the common foreign and security policy (CFSP). The method of construction of the two new pillars or edifices was based on intergovernmental cooperation, since the TEU required unanimity for decision-making and, hence, any Member State could veto a common action. A so-called "Social Protocol" excluded the United Kingdom from the social protection objectives of the TEC.
The essentially economic character of the Communities was surpassed, in order to allow the establishment of an entity with global character. According to Article B of the EU Treaty (Maastricht version), the Union set itself the following objectives:
- to promote economic and social progress which is balanced and sustainable, in particular through the creation of an area without internal frontiers [see section 6.1], through the strengthening of economic and social cohesion [see section 12.1.2.] and through the establishment of economic and monetary union, including ultimately a single currency [see chapter 7];
- to assert its identity on the international stage, in particular through the implementation of a common foreign and security policy including the eventual framing of a common defence policy, which might in time lead to a common defence [see section 8.2];
- to strengthen the protection of the rights and interests of the nationals of its Member States through the introduction of a citizenship of the Union [see section 9.1.];
- to develop close cooperation on justice and home affairs [see section 8.1];
- to maintain in full the "acquis communautaire" [see section 3.3] and build on it with the aim of ensuring the effectiveness of the mechanisms and the institutions of the Community [see chapter 4].
Thus, since the implementation of the Treaty of Maastricht in 1992, the European Union accompanied and complemented the European Community and we spoke about the European Community/Union (EC/EU), until the coming into force of the Treaty of Lisbon, the 1st December 2009, which abolished the European Community and bestowed legal personality to the European Union alone [see section 3.1].
The European Union was enlarged to fifteen Member States, on 1st January 1995, by way of the Treaties of Accession of Austria, Sweden and Finland, signed on 24 June 1994 at the European Council meeting in Corfu [OJ L 1, 01.01.1995]. The Accession Treaty of Norway had also been signed at that occasion, but, again, the Norwegian people voted against membership of the Union by a majority of 52.8%.