The European Treaties might be amended by using one of three different procedures. These procedures are rarely used, but are of great importance for the functioning of the European Union and the way decisions are made within the European Union.
The member states of the European Union in both revision-procedures take center stage through the European Council, the Council of Ministers and their national parliaments. The European Parliament and the European Commission primarily have an advisory role.
For some policy areas, European treaties specifically state how the decision-making can be modified and which procedure applies in these areas. The rules for this type of amendment to the Treaties is governed by the passerelle procedure.