This book deals with the question of the immunity of state agents before international criminal courts, and more specifically before the International Criminal Court (ICC). To do so, we have taken as our starting point a concrete case concerning the enforceability or otherwise of Vladimir Putin’s personal immunity as Head of State not party to the Rome Statute. Since March 17, 2023, an arrest warrant has been out for him for acts constituting war crimes. This situation raises two major issues in international law: on the one hand, whether or not his personal immunity is excluded by the Rome Statute (article 27 2), and on the other, whether or not States parties to the Rome Statute are under an obligation to cooperate with the ICC (article 98 1). It is this issue that has been examined throughout this study, in accordance with positive international law.