Originally, the Schengen agreements and the rules adopted between them worked independently of the European Union. However, in 1999, the Treaty of Amsterdam introduced them into EU law, while they provided exemptions for the only two EU Member States that had remained outside the territory: Ireland and the United Kingdom (which withdrew from the EU in 2020). Schengen is now a central element of EU law and all EU Member States that have not yet joined the Schengen area are legally obliged to do so if technical requirements are met. Several non-EU countries are included in this area.  The two Schengen agreements have been a major step forward for transport in Europe. Queues would often be one kilometre long and wait for border patrols to sign them, but the agreements helped to stop them. Today, people can enter neighbouring countries without having to present any form of identity card. Of course, airlines always require you to show it for security reasons, but border controls are much easier to navigate and don`t even exist in some cases. The November 13 attacks in Paris, which killed 130 people, led to an urgent change of mentality in the Schengen agreements. Countries have repeatedly extended controls on the basis of national authorities, referring to “the security situation in Europe and threats related to major secondary movements.” France has never received a recommendation from the Council to reintroduce border controls, but has maintained them permanently, citing a “persistent terrorist threat”. Indeed, the Schengen Agreement paved the way for the release of the Schengen visa. Although this is not part of the original provisions of the agreement, the top 15 countries need only a visa for all. The Schengen visa may allow non-EU members to travel freely to the countries participating in the programme.
There are currently 26 Schengen Member States. Most of them are members of the European Union (EU). However, two EU countries, the United Kingdom and Ireland, have chosen to leave Schengen. Other countries soon signed Schengen, starting with Italy in 1990, Portugal in 1991, Spain in 1992, Austria in 1995 and Finland, Sweden and Denmark in 1996. In December 1996, two non-EU states, Norway and Iceland, signed an association agreement with the countries that signed the Schengen accession agreement.