Why does the International Criminal Court fall short of expectations? This book contends that the answer lies in the governance role of the Assembly of States Parties, the Court's central, yet often overlooked, institutional body. Far beyond a diplomatic forum, the Assembly retains a crucial role in electing judges and prosecutors, adopting the budget, amending legal texts, and overseeing cooperation. Based on original research and previously unexamined official documents, it offers the first comprehensive analysis of the Assembly's history and practice from 2002 to 2021. The book discusses the Assembly in the context of "international judicial governance institution" (injugovin), positioning it within broader debates on international law and global governance. By dissecting the Assembly's functions, Jimenez Martinez shows how States Parties have collectively shaped, and at times constrained, the Court's evolution. As such, the book argues that the Court's challenges are not merely judicial, they are governance problems.