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European Union Law: EU Treaties

An introductory guide to the law of the European Union

Resources on EU Treaties & Constitutional Law

Here are some of the resources on EU constitutional law and treaties available through the UIUC Library system. Search the catalog for additional resources.

Treaties Are the Primary Source of European Union Law

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All European Union law is derived from the treaties between the EU Member States.  The treaties function as the EU's de facto constitution, defining both the allocation of powers between the EU and the Member States and the allocation of powers among the EU's institutions.  The EU may act only with respect the "competences" (policy areas) granted to it by the treaties.  The treaties cannot be amended without the consent of the Member States.

The Foundational Treaties

The two principal treaties on which the EU is based are now known as the Treaty on the European Union (TEU) and the Treaty on the Functioning of the European Union (TFEU).  Both treaties have been amended repeatedly since they originally came into force, most recently by the Treaty of Lisbon in 2009.

  • Treaty on the European Union  The TEU originally was known as the Maastricht Treaty, named for the city in the Netherlands in which it was signed in 1992.  In its original form, the TEU changed the name of what had previously been known as the European Economic Community (EEC) to the European Union and established the criteria for the Member States to form a monetary union.
  • Treaty on the Functioning of the European Union  The TFEU originally was known as the Treaty of Rome, which was signed in 1957 by the six founding members of the European Economic Community, the institutional predecessor to the EU.  In its original form, the TFEU established the EEC as a customs union and a common market for goods, services, capital, and labor.

The EU has compiled a consolidated version of its foundational treaties, encompassing both the TEU and the TFEU in their current, amended forms.  The consolidated treaties are freely available for download from EUR-Lex, the EU's online legal information database.

The Amending Treaties

Listed below, in reverse chronological order, are the treaties that have amended the EU's foundational treaties.  The year in which each treaty became effective is noted in parentheses.

  • Treaty of Lisbon (2009)  Key changes made by the Lisbon Treaty included the increased use of qualified majority voting in the European Council on certain issues, the establishment of a President of the European Council, enhanced powers for the European Parliament, and the formal recognition of the EU Council as the upper chamber of the EU's legislature.
  • Treaty of Nice (2003)  The Treaty of Nice reformed the institutional structure of the EU to facilitate its expansion into Eastern Europe to encompass countries that were formerly part of the Soviet Bloc.
  • Treaty of Amsterdam (1999)  The Treaty of Amsterdam authorized the EU to legislate on matters of immigration to facilitate the free movement of citizens within the EU, provided for the development of a common foreign and security policy, and increased inter-governmental cooperation in the field of criminal law.  It also included provisions to increase the power of the European Parliament and make the European Commission more accountable.
  • The Single European Act (1986) Major provisions included the introduction of qualified majority voting with respect to a limited range of policy matters and the establishment of a more collaborative legislative process in which the European Parliament would play a meaningful role for the first time.

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