When a country applies to join the EU it agrees to sign up to everything that has previously been agreed by the member states since the EEC was founded - the "acquis communautaire". The acquis ranges from procedures to monitor the habitats of wild birds, to regulations covering the administration of agricultural markets, to the hundreds of pieces of legislation necessary to implement the single market . . . an estimated 90,000 pages of rules, laws and administrative procedures. The process of checking the applicant against this formidable list, known as screening, is a prelude to formal accession negotiations and takes several years.
In the case of the incorporation into the EU of the Schengen provisions on passport-free travel some 1,500 pages of acquis are involved. These include procedures for handling travellers, stamdards of security at external frontiers, procedures for maintaining and accessing a common computer database, common standards for ID documents . . .