No part of this thesis may be copied, reproduced or transmitted without prior permission of the author This thesis is the culmination of several years of work, mostly at the European University Institute, but also at the European Court of Justice and at Columbia Law School. My gratitude goes to all those who helped me complete this project. I am particularly grateful to my supervisor, Giorgio Monti, for his invaluable guidance and support, and to Marise Cremona, Leigh Hancher and José María Rodríguez de Santiago, who generously accepted to be on my examining board. I am also grateful to Heike Schweitzer, who guided me through the first stages of my research, and to Christophe Giolito and Jorge Piernas, who shared with me, on many occasions, their State aid expertise. I thank Advocate General Cruz Villalón, who gave me the opportunity to do a stage in his cabinet and to learn from Ana Santamaría, Dimitry Berberoff, Juan Luis Requejo, Flavien Mariatte and, above all, Daniel Sarmiento. Special thanks also go to Anu Bradford, under whose supervision I worked during my LL.M. studies at Columbia. I thank Francisco Velasco Caballero, who allowed me to form part of his team at the Universidad Autónoma de Madrid and to broaden my horizons beyond the topic of this doctoral dissertation. Everyone at the Área de Derecho Administrativo and at the Instituto de Derecho Local has my appreciation, but Silvia Díez Sastre and Sofia Simou deserve special recognition. At the Universidad Autónoma de Madrid I also thank Javier Díez-Hochleitner and Carmen Martínez Capdevila, who initiated me into EU law, and Juan Arrieta, without whose encouragement I would never have undertaken this project in the first place. I have been fortunate to share the joys and tribulations of the doctorate with a lot of people,
