Relations between Iceland and Norway, on the one hand, and Ireland and the United Kingdom, on the other, in the areas of the Schengen acquis applicable to Iceland and Norway are governed by an agreement approved by the Council of the European Union on 28 June 1999. In December 1996, two non-EU states, Norway and Iceland, signed an association agreement with the countries that signed the Schengen accession agreement. Although this agreement never entered into force, the two countries were part of the Schengen area following similar agreements with the EU.  The Schengen Agreement itself was not signed by non-EU states.  In 2009, Switzerland officially concluded its accession to the Schengen area by adopting an association agreement by referendum in 2005.  Now that the Schengen Agreement is part of the Community acquis, it has lost to EU members the treaty status which could only be changed on its terms. Instead, changes are made in accordance with the EU`s legislative procedure under the EU treaties.  Ratification by the former signatory states is not necessary to amend or repeal all or part of the previous Schengen acquis.  Acts setting out the conditions for accession to the Schengen area are now adopted by a majority of the EU`s legislative bodies. The new EU Member States do not sign the Schengen Agreement as such, but are required to implement the Schengen rules within the framework of existing EU legislation, which any new entrant must accept. [Citation required] This means that Schengen Member States that were not part of the EU have few formally binding options to influence the development and development of Schengen rules; their options are effectively reduced to approval or exit from the agreement. However, consultations are being held with the countries concerned prior to the adoption of certain new provisions.
 Originally, the Schengen treaties and the rules adopted were officially independent of the EEC and its successor, the European Union (EU). In 1999, the Treaty of Amsterdam incorporated them into EU law, which codified Schengen into EU law and also introduced opt-outs for Ireland and the Kingdom, the latter having taken place since its withdrawal from the EU.