Treaty establishing the European Community (Amsterdam consolidated version)

Article 18

1. Every citizen of the Union shall have the right to move and reside freely within the territory of the Member States, subject to the limitations and conditions laid down in this Treaty and by the measures adopted to give it effect.

2. The Council may adopt provisions with a view to facilitating the exercise of the rights referred to in paragraph 1; save as otherwise provided in this Treaty, the Council shall act in accordance with the procedure referred to in Article 251. The Council shall act unanimously throughout this procedure.