What is the Schengen Agreement?
The Schengen Agreement was signed on June 14, 1985 in Luxemburg by five EU countries, Тhis treaty led most of the European countries towards abolishment of their national borders and to build a Europe without borders known as “Schengen Area”.
Of the six EU members that are not part of the Schengen Area, four - Bulgaria, Croatia, Cyprus, and Romania—are legally obliged to join the area, while the other two - the Republic of Ireland and the United Kingdom—maintain opt-outs. The four European Free Trade Association (EFTA) member states, Iceland, Liechtenstein, Norway, and Switzerland, are not members of the EU, but have signed agreements to join the area. Three European microstates—Monaco, San Marino, and the Vatican City—are de facto part of the Schengen Area.