Framework Decision 2009/948/JHA on the prevention and settlement of conflicts of exercise of jurisdiction in criminal proceedings established an ad hoc procedure for settling conflicts of criminal jurisdiction based on the mutual exchange of information and the establishment of direct consultations between the competent authorities with a view to reaching consensus on an effective solution. However, neither common legally binding criteria for deciding the best jurisdiction nor specific rules for the transfer of proceedings (which can occur after parallel proceedings have been identified) were established in this instrument, or in any other instrument adopted by the EU to date. This book analyses the current EU legal framework on conflicts of jurisdiction and transfer of criminal proceedings, paying special attention to its numerous shortcomings and loopholes from a fundamental rights and due process of law perspective. The book begins with an assessment of the various principles and grounds used by Member States for claiming criminal jurisdiction. Secondly, de lege lata EU procedure on the settlement of conflicts of criminal jurisdiction, as well as its implementation in Spain and Italy, are thoroughly examined. After discussing the main principles and fundamental rights at stake, the author proposes two alternative and original de lege ferenda models for the prevention and settlement of conflicts of criminal jurisdiction and transfer of criminal proceedings, exploring the different possibilities offered by the EU’s primary law.