Integration into the European Union
The Treaty of Amsterdam, signed in 1997, formally incorporated Schengen into the framework of the European Union as the Schengen acquis. The Schengen acquis includes the Schengen Agreement of 1985, the Schengen Convention of 1990, as well as various decisions and agreements adopted in Schengen’s implementation. When the Amsterdam Treaty came into force in 1999, decision-making power for Schengen came under the Council of Ministers of the EU.
Although Schengen had officially become part of the EU, the agreement did not apply to all Member States. The United Kingdom initially opted out, preferring to maintain its own national borders. Ireland followed suit in order to maintain its Common Travel Area with the UK.
However, the UK and Ireland do participate in some aspects of Schengen, including the Schengen Information System. Iceland and Norway also signed an agreement with the EU in 1999 to continue their participation in the Schengen area.
Schengen and EU Enlargement
While the 10 new Member States that joined the EU in 2004 are expected to eventually implement the full Schengen acquis, they have not yet, in the eyes of the existing Schengen states, met the requirements involved in the acquis.
