Differentiated Integration of Core State Powers at the EU’s External Borders

This article examines the European Union’s (EU) approach to external borders, migration and asylum, which has been strongly marked by differentiated integration (DI). Instead of looking at formal opt-out in legislation, decision-making, and common standards building, which has been extensively studied, this article shifts its focus towards DI in everyday policy implementation and crisis management. It explores the solution package that EU policy-makers offer to the Member States experiencing unprecedented migratory pressure, which involves the direct engagement of EU bodies, such as the European Border and Coast Guard (Frontex) and the European Union Agency for Asylum (EUAA). While Member States are not obliged to participate in these initiatives for joint implementation whereby EU agencies and national administrations work side by side in implementing common European policies on border controls and asylum, differentiation in policy engagement occurs when some Member States accept the EU’s offer while others do not. To interrogate the consequences of such "soft" differentiation in crisis management, this article looks at three particular cases: Malta’s refusal to host joint sea operations led by the European Border and Coast Guard (Frontex) in 2010, Spain’s refusal to implement the hotspot approach during the 2015 migration crisis, and Poland’s rejection of involving Frontex and EUAA in border controls during the 2021 EU-Belarus border crisis. Findings suggest that such "soft" opt-out did not necessarily lead to multi-speed or permanent differentiation, but rather opt-in by alternative means. While DI can be resilient and path-dependent, there has been a convergence in crisis response and a normalisation of joint implementation. Relying on the analysis of official documents and on semi-structured elite interviews that were conducted between 2021 and 2023, this article not only contributes to the understanding of the EU’s integration of core state powers, but also offers insights into the EU accession perspectives of the Western Balkans, Ukraine, Moldova, and Georgia, which might be the new frontline Member States of the EU/Schengen.