In 2008, the introduction of the EU's Framework Decision - the principle of mutual recognition of judgments in criminal matters, imposing custodial sentences or measures involving deprivation of liberty for the purpose of their enforcement - sparked discussions as to whether the practical operation of the instrument would be compatible with its very objective, being the enhancement of detained persons' social rehabilitation prospects. Transferring detained people back to their respective Member State of residence and/or nationality within the mutual recognition framework is somewhat precarious in light of the variety of Member States' legal and prison systems. In this context, and following a call for tender by the European Commission, the authors of this book conducted the largest study to date on Member States' material detention conditions, early/conditional release provisions, and sentence execution modalities. In addition to exploring the diversity of legal frameworks, the study also assessed practitioners' views on the cross-border execution of custodial sentences in the EU. This book contains EU-level legal and practitioners' analyses, as well as the high level final report to the study, confirming preliminary concerns that flanking measures are urgently needed for a proper operation of the Framework Decision. It will be essential reading for policy makers, judicial and law enforcement authorities, and defense lawyers. Additionally, it will be an asset to everyone who is involved in or taking an interest in detention issues and cross-border execution of judgements involving deprivation of liberty in the EU. (Series: Institute for International Research on Criminal Policy IRCP] - Vol. 40)