THE CO-DECISION OR ORDINARY LEGISLATIVE PROCEDURE
One of the important changes introduced by the Lisbon Treaty (or the Treaty of the European Union (TEU) and the Treaty of the Functioning of the European Union (TFEU)) is the fact that co-decision becomes the "ordinary legislative procedure", i.e. what used to be the exception in decision-making has become the norm for most policy areas.
As defined in Article 294 of the TFEU, the co-decision procedure is the legislative process which is central to the Community's decision-making system. It is based on the principle of parity and means that neither institution (European Parliament or Council) may adopt legislation without the other's assent.
Having been established by the Maastricht Treaty, and extended and adapted by the Treaty of Amsterdam, where it was also made more effective, and the Treaty of Nice, the co-decision procedure now covers more than 80 areas under the first pillar (based on the Treaty on the Functioning of the European Union - TFEU).
Since the entry into force of the Amsterdam Treaty until 30 June 2009, some 900 co-decision procedures have been successfully completed (apart from three cases). Some more statistics and background information is available on this site.
In addition, the site contains the following references:
Furthermore, the following texts are useful for the understanding and application of co-decision. They were agreed before the entry into force of the Lisbon Treaty, thus any reference to "co-decision" should be read as a reference to the "ordinary legislative procedure":
Joint Declaration on practical arrangements for the co-decision procedure
(serves as a practical reference framework for the three institution as regards the role it has to play at the various stages of the procedure)
(annexed to the Treaty of Amsterdam calls on the institutions to make every effort to ensure that the co-decision procedure operates as expeditiously as possible and in particular that in no case should the actual period between the second reading by the European Parliament and the outcome of the Conciliation Committee exceed nine months)
Interinstitutional agreement on "better lawmaking"
(sets out best practice and lays down new objectives and commitments, including: the improvement of interinstitutional coordination and transparency, the establishment of a sound framework for "alternative instruments", the increased used of impact analyses in the Community decision-making process and the desire to establish a mandatory time limit for transposing directives into national law)
Code of conduct for negotiating in the context of the ordinary legislative procedures: Annex XX of the Rules of Procedure of the European Parliament
(This code of conduct as adopted as part of the Rules of Procedure in July 2009 for the 7 th parliamentary legislature sets out general principles within European Parliament, on how to conduct negotiations during all stages of the ordinary legislative procedure with the aim of increasing their transparency and accountability, especially at an early stage of the procedure. It is complementary to the "Joint Declaration on practical arrangements for the codecision procedure" agreed between Parliament, Council and the Commission which focuses more on the relationship between these institutions.)