The choice of the word “flexibility” in the title of this paper rather than the term “closer co-operation” introduced by the Treaty of Amsterdam is not accidental: since the general Amsterdam provisions on closer co-operation have not so far been used, a paper on the experience of those provisions since their entry into force would be very short—even if they have given rise to an extensive literature. It should nevertheless be remembered that under the terms of the Amsterdam Treaty itself there are situations where those provisions are deemed to have been used: under Article 1 of the Protocol Integrating the Schengen acquis into the Framework of the European Union, Belgium, Denmark, Germany, Greece, Spain, France, Italy, Luxembourg, the Netherlands, Austria, Portugal, Finland and Sweden, as signatories to the Schengen agreements, are “authorised to establish closer co-operation among themselves” within the scope of those agreements and related provisions; furthermore, under Article 5 of that Protocol, where either Ireland or the United Kingdom or both have not notified the President of the Council in writing within a reasonable period that they wish to take part,
“the authorisation referred to in Article 11 of the Treaty establishing the European Community or Article 40 of the Treaty on European Union shall be deemed to have been granted to the Member States referred to in Article 1 and to Ireland or the United Kingdom where either of them wishes to take part in the areas of co-operation in question”.