The Schengen Agreement of 1985 and the Convention implementing the Schengen Agreement, which entered into force in 1995, led to the abolition of checks at the internal borders of the signatory states –creating the Schengen area– and established common standards for controls at external borders, as well as common rules for the issuance of visas and the granting of asylum, in order to ensure that the free movement of people within the EU can take place in a safe environment.
Regarding the free movement of people, the most important measure taken is the creation and operation of a common information system, the Schengen Information System (SIS), the aim of which is to improve cooperation between police and judicial authorities. The SIS is a database that allows the competent authorities of the Schengen states to exchange data on certain categories of persons and objects. In particular, it includes information on persons wanted by the judicial authorities, undesirable foreigners, missing persons and persons who are under discreet surveillance, as well as stolen objects.
The second generation Schengen Information System (SIS II), which entered into operation in 2013, is characterized by improved functions, such as the possibility of using biometric data, creating a new type of alerts, and connecting several alerts to one another (such as an alert for a person with an alert for a vehicle).
Each state is responsible for the establishment and operation of its own national system, namely N.SIS II. In order to facilitate the exchange of additional information between the Schengen states on the entries in the SIS, the SIRENE (Supplementary Information Request at the National Entry) Offices have been set up in all the Schengen states.
Their main tasks are to enter alerts in the SIS and to impose the appropriate measures. The SIRENE Offices are a single contact point for all national law enforcement authorities participating in the SIS and for police cooperation in the Schengen area, operating on a 24-hour basis (for more information you can visit the following websites: SIRENE – Schengen Information System, National SIRENE Offices).