The book offers a legal understanding regarding which core elements characterize an SGEI, 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. The book also analyses 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 in Sweden. The book includes propositions on crucial but yet unsettled legal questions, and is therefore mainly aimed at legal academics and practitioners but may also be of interest to political scientists.