This book is the result of a long period of research, and therefore, there is also a long list of institutions and people I am in debt to. This study was mainly carried out at the Max-Planck Institute of Foreign and International Criminal Law (Freiburg i.Br., Germany) and contains a great part of the results of research supported by the Alexander von Humboldt Foundation. Without the generous support of the Humboldt Foundation and the hospitality and assistance of Prof. Dr. Dr. h.c. mult. Ulrich Sieber (director of the Criminal Law Department at the Max- Planck Institute), this would certainly have been impossible, and it is therefore difficult for me to find the appropriate words to express the gratitude I feel towards both of them. I am also grateful to the Law Faculty at Basel University and to Prof. Dr. Sabine Gle?, especially for her support and hospitality in her department during the 2 months of May and June 2016. Moreover, I wish to thank the Law Department at Messina University, which organised excellent arrangements to cover my long absence from Sicily. A special thank you goes, once again, to Springer Verlag and especially to Dr. Brigitte Reschke for her patience and interest shown in this research.