While the profound transformation and ensuing disintegration of the Ottoman empire from 1839-1923 has been conventionally summarized as an interim stage before the ultimate triumph of ethnic nationalism and secular modernity in the Middle East, this popular narrative elides the fiercely contested nature of institutional changes in the region. In particular, such accounts marginalize the acute struggles of scholars, statesmen, and everyday citizens to constitute alternative modernities not rooted in strictly secular-liberal or eurocentric cultural epistemes. The “Nizamnama” codes of King Amanullah Khan of Afghanistan (r. 1919-1929) and his transnational team of Islamic jurists represented one such project. Compared to the nation-building campaigns of Mustafa Kemal “Atatürk” of Turkey or Reza Shah Pehlavi in Iran, or even the British and French mandates of the post-WWI Near East, Amanullah’s route shares many parallels but in the end represented a different path of modern state formation. Though also an attempt at “social engineering” through law, unlike the aforementioned regimes the Nizamnama codes of the 1920s was an endeavor to circumvent the widening gulf between “Islamic” and “Secular,” a dualism whose roots were laid in several Muslim-majority countries at precisely the same time, and have been hotly debated ever since. In this way, I argue, Amanullah Khan’s Nizamnama represented the twentieth century’s first movement to constitutionalize Islamic jurisprudence in a modern nation-state, establishing a bold precedent for Muslim modernists in power decades before the creation of the better-studied “Islamic Republics” of Pakistan (1947) and Iran (1979). In sum, my dissertation is a transnational history of the individuals, institutions, and ideas behind the Nizamnama codification project in Afghanistan. Based on archival research in Turkey, England, India, and Afghanistan, the study culminates with an exploration of the competing roles of Ottoman lawyers from Istanbul and Islamic legal scholars from northern India who traveled to Kabul to participate in the production of the first constitution of Afghanistan (1923) and associated Nizamnama codes from 1919 to 1924. The dissertation also unearths a deeper history of juridical links between Ottoman Turkey, British India, and Afghanistan as early as the 1860s, which I argue laid the foundations for Amanullah’s path-breaking project roughly half a century later.