Certain matters in the Council of Ministers are decided by unanimous voting and certain by qualified majority voting. The distinction is laid down in treaties and cannot normally be changed without a new treaty. Under the passerelle clause, voting on certain areas can switch from unanimity to QMV if the European Council unanimously approves this. This decision cannot be later reversed without treaty change.
There are currently four current passerelle provisions:
In 2004 the European Council used the passerelle clause to move to QMV on asylum and immigration
The unratified European Constitution proposed passerelle provisions on: