This collection examines the interface or interaction between European Union law and national law, in particular at assessing the delineation of competences between the EU and its member states regarding various policy areas. The book not only investigates the controversial aspects of the EU- national law relationship, but it presents recommendations for guiding the interface between EU and national rules in specific domains. Consequently, its objective is the production of guidelines for governing interactive correlations, not yet clearly defined, between EU and national legal norms in particular fields. More specifically, the following questions will be dealt with: - Are there some policy areas lacking any interaction between EU and national rules? - What are the remaining or residual competences left to the member states/national law? - If there are remaining powers for the member states, are they actually exercised and, if so, in accordance with which principles?