The Common Foreign and Security Policy provisions of the Maastricht Treaty, provide for the EU to "request the Western European Union, which is an integral part of the Union, to elaborate and implement decisions and actions of the Union which have defence implications ", Article J. 4. In this context, the Western European Union has committed itself to develop its operational capacity so that it could respond to such requests from the EU.
In its Petersberg Declaration of June 1992, the Western European Union decided that it should develop its operational capacity, particularly with a view to humanitarian and rescue tasks, peacekeeping tasks and crisis management — what have become known as the "Petersberg tasks". It is generally accepted that, in the new security situation in Europe, the Petersberg tasks would usually be conducted at the request of the UN, the OSCE, or the EU, in accordance with Title V of the Maastricht Treaty.
Since the ratification of the Maastricht Treaty one such request has been made by the EU to the Western European Union, namely to provide the police element for the EU's Administration of Mostar. Members of the Western European Union are providing police contingents for the Mostar operation. Recently, Austria, Finland and Sweden as Western European Union observers, announced their intention of providing police for the operation, and they have expressed their general interest in involvement in Western European Union Petersberg tasks, based on their long UN peacekeeping and humanitarian experience.