This book is the result of a doctoral thesis accepted by the University of Mannheim in Germany. It was written during my time as a research fellow at the Chair for Public Law and Legal Philosophy at that university. The manuscript reflects the legal situation and case-law as of December 2016. I wish to express my deep gratefulness to my doctoral supervisor, Professor Dr. Hans-Joachim Cremer, who gave me the opportunity to combine my academic interest in public international law with a topic that was of personal importance to me. With his encouragement and dedication as my supervisor and mentor over the past years, he has become a role model for me, both personally and professionally. Professor Dr. Eibe Riedel kindly undertook the second evaluation of my doctoral thesis, for which I am very thankful. I am very grateful for the excellent research opportunities granted at the Max Planck Institute for Comparative Public Law and International Law in Heidelberg. As most of this book was written in Heidelberg, I would further like to thank my sister Sandra and her family, and all my Heidelberger friends and colleagues for a wonderful time, their moral support, the numerous legal discussions we had and for all the constructive critique I received. Finally, I want to thank my parents with all my heart for their unconditional support during my education and through my life. I dedicate this book to them.