The Maastricht Treaty or Treaty of the European Union TEU was signed in the Dutch city of Maastricht on February 7, 1992, and later entered into force on November 1 of the following year. With the presence of the President of the European Parliament at the time, Egon Klepsch, the EEC became EC (from the European Economic Community to the European Community), seeking from the nomenclature to provide a greater sense of breadth and significance of the European project.

Since the signing, the EU is based on the following three pillars; the European Communities, the CFSP (Common Foreign and Security Policy) and the JHA (Justice and Home Affairs).

The Maastricht Treaty in question contains advances in the legislative and control powers of the European Parliament, increasing its authority by introducing the codecision procedure and expanding the cooperation procedure. The EP then has the right to ask the Commission to submit legislative proposals on matters that it considers require the adoption of a Community act.

This very moment in European history represents a serious turning point for the national sovereignty of each member of the Union, since it is certainly affected, even subjected, to binding normative decisions coming from external supranational institutions. This entails problems around the jurisdictional powers of each nation over its citizens, falling for the first time the notion of popular sovereignty since Westphalia.

Although this change in the regulatory hierarchy of European countries begins in Maastricht, it does not stop there but continues to escalate, reaching the entry into force of the Lisbon Treaty in December 2009. This new agreement is going to replace the pillars that have earlier been mentioned by a community method to which most of the EU policies will be subject.

We will soon see that EU law is made up of primary law and secondary law. Neither of them includes the constitutions of each country of the Union, we speak instead of a “constitutional block”. Such a block supposes a legal body of the highest normative rank, integrating the European Treaty and its reforms, which without being formally constitutional, come to condition other norms of the same form and rank. This block is waiting for a redefinition before generating constitutional problems, since it is clear that the EU will end up integrated as a last response to major causes, but along the way, subordinating the sovereignty of the states will not be an easy task.

Primary law comprises the EU Treaties, which are binding agreements between EU member countries, the Charter of Fundamental Rights (since the Lisbon Treaty), and the general principles established by the Court of Justice of the Union European.

While the secondary includes international agreements with both states and organizations, as well as other types of acts - regulations, directives, decisions, recommendations and opinions-, specified in article 288 of the Treaty on the Functioning of the EU (TFEU). Likewise, maintaining jurisdiction as a supranational entity above the member states.

According to the principle of competencies, in theory the EU has only those competencies that have been granted to it by its member countries through treaties. The issue of enabling clauses appears. The "constitutional block" that has been referred before, can be defined by the norms that integrate it; the Constitution, the Constitutive Treaty and the Statutes of Autonomy.

Article 93 of the Spanish Constitution states that an organic law may authorize the conclusion of treaties by which the exercise of powers derived from the Constitution is attributed to an international organization or institution […]. Therefore, this would be the enabling clause that constitutes and provides the necessary coverage for the "constitutional block" to be integrated.

Victor Hugo, in his opening speech at the 1849 Peace Congress in Paris, said <<all of you, nations of the continent, without losing your distinct qualities and your glorious individuality, will merge closely into a superior unity>>. As well as the Maastricht Treaty, which came more than a century later to make this romantic vocation a reality, if considered in its historical context both by action and by omission, comes to overcome the strictly community framework, taking an unprecedented step in terms of theory of law and intergovernmental concerns.