How does EU legislation impact the Member States? Arguably, no other issue is more closely connected to national sovereignty. However, existing research has thus far failed to deliver a univocal answer to this question. Instead, quantitative research – from political scientists and public administration scholars – has resulted in very diverging conclusions. By contrast, the legal perspective on the relationship between the EU and its Member States has been dominated by a focus on the principles of conferral and subsidiarity, as well as on the delineation and use of EU powers. Such an approach makes it equally difficult to identify the actual and concrete impact of EU legislation. Yet, it is contended in this contribution that a legal perspective, focusing on the actual content of EU legislation, is needed to come to a better understanding of the EU’s legislative impact on the Member States.

The scope of application and the added value of EU legislation as well as national discretion therein are three key elements for determining the impact of EU legislation. The scope of application concerns the situations covered by EU legislation; added value regards the question of how EU legislation relates to other (pre-existing, overarching and adjacent) EU law. Policy choices and other room for manoeuvre for the Member States included in EU legislation makes for national discretion. Examples may be open norms or non-defined terms and concepts and the possibility to apply exceptions at the national level to general rules of EU legislation. Three areas of EU law are compared, each with a focus on a particular legislative act: migration law (the Family Reunification Directive); freedom to provide services (the Services Directive) and criminal law (the Framework decision on the European Arrest Warrant).