In the early 2000’s, due to the enlargement of the European Union (EU) with a significant number of new members, an institutional reform was necessary in order to avoid a paralysed decision-making system. The system set up in 1950 for a Community which comprised six Member States was no longer operating efficiently within a Union of 15 and, subsequently, 25 Member States.

The process of adoption of three important tools - The Nice Treaty, the Treaty establishing a Constitution for Europe and the Lisbon Treaty - lead to numerous fundamental and institutional problems that had to be dealt with.

The Nice Treaty was concluded on December 11, 2000 and signed on February 26, 2001, presented not only as a treaty of institutional reform, but also as a step towards the constitutionalisation of the European Union. An argument for this is the proclamation of the Charter of Fundamental Rights. The Reform Treaty, also named the Lisbon Treaty, entered into force on December 1, 2009, and was meant to be a more successful version of the Treaty establishing a Constitution for Europe.

A substantial difference between the Nice Treaty, the Lisbon Treaty and the Constitutional Treaty represents the objective sought by each of them.  The Treaty of Nice was aimed to ensure an institutional system for a Union consisting of nearly 30 Member States. In contrast, the Constitutional Treaty was setting up a new legal instrument containing rules easily understandable by the Member States’ nationals, which also emphasised the symbolic idea of ‘Constitution”’ This Treaty was output as a consequence of the existing treaties, which did not happen in the case of the Nice Treaty and the Lisbon Treaty, as they were maintaining an effective legislative framework. The simplification of the treaties was an objective to be attained post-Nice; however, unsuccessfully, taking out of force the existing treaties and the entry into force of the Constitutional Treaty did not take place.

From an evolutionary point of view, if up to the Treaty of Nice, the competences of the European Union were not specifically mentioned, beginning with the Constitutional Treaty, a classification has been carried out, which, at present, is to be found in the Treaty of Lisbon.  It cannot be denied that this is an ‘element of substantial progress made in the European construction’, whereas such an approach simplifies and clarifies the Union's actions and shall give them an increase of democracy, with regard to the benefits of transparency for nationals of Member States.

After the Nice Treaty, the role of national Parliaments has been brought into discussion, the provisions of the Constitutional Treaty being further accepted in the framework of the Treaty of Lisbon. In order to ensure a higher degree of transparency, certain obligations had to be introduced for European institutions: to cooperate and collaborate with national Parliaments, to respect certain basic principles of the European Union’s law, namely those of subsidiarity and proportionality. In addition to the obligations imposed upon European institutions, the competence of national Parliaments was regulated, primarily in what concerns their power to influence decision-making at Union level by means of different procedures.

Among the objectives to be attained which were questioned at the time the Nice Treaty was prepared, we can also find issues introduced by the Constitutional Treaty, in turn taken over or not by the Treaty of Lisbon. Among them, we can mention the principles of subsidiarity and proportionality, which found a new justification in the light of the provisions regarding the allocation of competences, newly introduced by the Constitutional Treaty.  The same principles can now all be found within Protocol no. 2 annexed to the Lisbon Treaty.  The principle of supremacy of EU law was not specifically mentioned by the Treaty of Nice, being later developed by the European Union’s Court of Justice. The Constitutional Treaty included it in its text, but, upon entry into force of the Treaty of Lisbon, it remained at the level of unwritten principle of the EU, being referred to only in a Declaration annexed to the Treaty.

The Constitutional Treaty has a characteristic symbolic and legal load that also comes from the ‘constitution element’ found in its title. It even regulates the symbols of the European Union, such as the flag, the anthem, the currency, the day of Europe, for an even greater emotional significance, a highlighted European identity. In addition, it contained specific names: ‘European laws’ for regulations, and ‘European framework laws’ for directives. Because of this deep symbolic load which it had for nationals of Member States, the Treaty of Lisbon did not choose to use them. The citizens were not prepared for such an involvement and dedication to the idea of a European identity.

Among the common elements of the Treaty establishing a Constitution for Europe and the Treaty of Lisbon, we can also find the ‘citizen initiative’. The citizens can directly ask the Commission to propose an initiative that is of interest to them and which is related to the EU competence, by adding together one million signatures from various Member States. Both devote strengthened protection for citizens through the provisions relating to the space of freedom, security and justice laid down by the Constitutional Treaty, and mention the formation of a European Prosecutor's Office. 

An element embraced by the three treaties which are the subject of our study is represented by the Charter of Fundamental Rights of the European Union.  In the summit of the European Council in Nice in December 2000, it was solemnly proclaimed by the Commission, Parliament and Council of the European Union and approved by the Member States, but its legal status has been put on the list of objectives post-Nice.  In 2004, the Constitutional Treaty incorporated in its second part the Charter provisions, giving it legal compulsory value, also regulating the European citizenship, an idea taken over by the Treaty of Lisbon as well.  Subsequently, the Lisbon Treaty has provided the legal value of the Charter as being equal to that of the treaties, but, unlike the Constitutional Treaty, it was not built in, but annexed to the Treaty.  The adoption of a catalogue of human rights brought about a change on the initial economic objectives of the EU.

One of the fundamental news brought after the Nice Treaty is the opportunity of a Member State to be able to withdraw from the European Union, established by the Constitutional Treaty, and maintained by the Lisbon Treaty, as a guarantee of their sovereignty. 

With regard to the relationship between the EU and the Member States, we must mention the first express regulation of the legal personality of the Union by the Constitutional Treaty and then the Lisbon Treaty.  

To conclude, the three treaties derive from one another, as a result of an evolutionary process of the enlarged European Union. The Constitutional Treaty might be considered an evolved form of the Treaty of Nice, whereas the Lisbon Treaty is a ‘mild’ form of the ’Constitution’. Even if the bond between Nice and Lisbon was less successful, it was not a less important Constitutional attempt, which made the transition easy.