In the face of current confusion regarding the use of articles 290 and 291 TFEU, there is a need to further develop the theory of legislative delegation in the EU Commission. This timely book approaches this question from a practical perspective with a detailed examination of how the legislator uses delegated and implementing mandates in different fields of EU law.Offering an analysis of legislative practice and providing concrete evidence of how articles 290 and 291 TFEU are actually handled, the expert contributors offer new insights into potential developments in EU administrative law. From this emerges a tentative categorisation that separates delegated rule-making from implementing rule-making according to the differentiation of substantive and procedural matters. However, as difficulties in the categorisation continue to remain, the book explores their systemic reasons, deeply rooted in the unclear constitutional shape of the EU.The Legislative Choice Between Delegated and Implementing Acts in EU Law will be essential reading for law academics and course leaders as well as practitioners in national and EU administration interested in this ongoing debate central to EU administrative law. Contributors include: M. Chamon, J. Karsten, F. Lafarge, M. Ortino, A. Ott, S. Roettger-Wirtz, E. Tauschinsky, A. Vincze, W. Weiss, D. Zdobnoh