Primary legislation in the EU system refers to treaties. Types of treaties include those establishing the EU (the Founding Treaties plus amendments), Accession Treaties, conventions between member states, and treaties between the EU and third parties. The full text of these treaties, as well as consolidated versions incorporating amendments at various points in time, can be found at the Eur-Lex website.
Another source for EU treaty texts is Westlaw (WL Home > Content Types > International Materials > Jurisdictions > European Union > European Union Treaties). A good, albeit not current, print source for EU treaties is the Encyclopedia of European Union Law. Available at UIC Law Library - 10th Floor - KJE4442.3.E52.
The following founding and amending treaties are among the most important:
The Treaty of Rome (1957) is somewhat analogous to our federal Constitution in that it creates the EU institutions and defines EU objectives. It also provides the basis and authority for EU legislation. The Rome Treaty is premised on the idea of a regional government of limited or derived powers. The Treaty of Lisbon significantly amended the EU's two core treaties, the Rome Treaty (EC Treaty) and the Maastrict Treaty (TEU). The Rome Treaty has been renamed the Treaty on the Functioning of the European Union (TFEU). The following chart provides a useful summary of the main features of each treaty.
For guidance on citing EU Treaties, see The Blue Book Rule 21.9 - European Union.
See Treaties establishing the European Union from European Union Law: An Integrated Guide to Electronic and Print Research