Scope of Schengen Acquis in 2024

The substantive scope of the Schengen acquis as it presents itself in 2024 is not as clear and coherent as it should be from the perspective of legal certainty, due to historical developments and political decisions taken over the last decades, in the context of which legal and logical arguments were sometimes superseded by political considerations. The Schengen acquis can best be illustrated by the picture of an onion: The inner layers of that onion are uncontested and “pure” Schengen acquis. Legal developments in these fields have always and consistently been labelled as Schengen-related and include rules on abolishment of internal border control, harmonized provisions on external borders, visa, intra-Schengen mobility of foreigners, the Schengen information systems (SIS, VIS, EES, ETIAS) and Schengen Evaluation. The outer layers of the Schengen acquis are still closely related to Schengen and contain a number of provisions which are clearly considered as Schengen-related. These outer layers include: document security, return and readmission, irregular migration, police cooperation, judicial cooperation, drugs, firearms and data protection. The Schengen labelling in these layers happened in a less consistent way than in the inner layers and in many cases, Schengen-related acts and non-Schengen-related acts coexist side by side, even though they cover closely related substance matters. The outer layers of Schengen law are surrounded by an “aura” of subject matters that have a direct political linkage to the establishment and operation of an area without internal borders but which are, from a formal legal perspective, not considered as Schengen-related. They were either never considered as Schengen-related (such as the field of legal migration and substantive asylum law), or they were harmonized at EEC level before the creation of Schengen (such as free movement rules), or they only emerged as a relevant topic for Schengen in recent years (such as solidarity measures or responsibility rules for irregular migrants), or they lost their Schengen-relatedness in the course of history (such as Dublin, readmission and many developments in the field of police and judicial cooperation).