This book offers a legal understanding regarding the core elements of SGEI (Services of General Interest), and of how the post-Lisbon constitutional framework on SGEI affects the application of the EU market rules by the EU Court of Justice, including procurement rules, to public services. It is built up of three parts, namely Part I: No Exit from EU Market Law for Public Services, Part II: SGEI as a Constitutional Voice for Public Services in EU Law, and Part III: The cost of loyalty, the relationship between EU procurement and state aid legislation on social services and the Treaty rules on SGEI, ending with a case study of Swedish systems of choice. Analyses are also provided on how the EU legislator engages in the Europeanisation of social services through EU procurement and state aid rules that have an ambiguous relationship to the Treaty framework on SGEI. Some explanation to this ambiguity is proposed by studying how the application of EU state aid rules could hinder the development of Swedish systems of choice liberalizing publicly-funded elderly care and school education. Included are propositions on crucial but yet unsettled legal questions, in particular what the legal meaning and relevance of the notion of economic activity in EU market law are and which core elements characterize SGEI. This book is therefore mainly aimed at legal academics and practitioners but may also be of interest to political scientists. Caroline Wehlander studied at Umea University and holds the title of Doctor of Laws. She lives and works in Sweden.