The 1917 promulgation of a new Ottoman family law is recognized as a landmark moment in the history of Islamic law by scholars of women and gender in the Middle East. Yet the significance of the 1917 law in the struggle over religious jurisdiction, political power, and Ottoman sovereignty has been overlooked in the scholarship on both Ottoman legal reform and World War 1. Drawing on Ottoman Turkish, German, French, and English sources linking internal interpretations of the law and external reactions to its passage, we reinterpret adoption of the family law as a key moment in the geopolitics of World War 1. We demonstrate that passage of the law was a critical turning point in the wartime process of abrogating the capitulations and eliminating the last vestiges of legal extraterritoriality in the Ottoman Empire. The law is situated in its wartime political context and the geopolitical milieu of larger Europe to demonstrate that, although short-lived, the 1917 family law was a centerpiece of the wartime struggle to define extraterritorial rights of the Ottoman Empire, the Great Powers, and their protégés within the empire.