This book is based on my doctoral dissertation on “The right to personal self- defence as a general principle of law and its general application in international human rights law,” which was accepted by the Law Faculty of European University Viadrina in Frankfurt (Oder), Germany. I am deeply grateful to my thesis advisor, Professor Wolff Heintschel von Heinegg. I was persuaded that it was a good idea to start a doctorate and a family at the same time by his advice that “one is never too old to write a doctoral dissertation.” His wise guidance throughout the process, along with the swift second review by Professor Carmen Thiele, ensured that I completed my doctorate before actually becoming old. I am also thankful to Mona Rishmawi, Nathalie Prouvez and Francesca Marotta at the Office of the United Nations High Commissioner for Human Rights (OHCHR), who always encouraged me to maintain an academic outlook to complement my work. This book was written during a leave of absence from OHCHR, which I spent at the wonderful U.N.- mandated University for Peace in Costa Rica. I am indebted to Rector Francisco Rojas and Dean Juan Carlos Sainz- Borgo for hosting me as a visiting scholar and professor at UPEACE. All views expressed in this book remain solely my own and do not necessarily reflect those of the United Nations.