This paper explores the afterlife of the Ottoman Islamic endowment (Awqaf/Evkaf) as a transimperial institution in its successor nation-states. I analyze how the negotiations between Ottoman, Egyptian, and European statesmen, in the period following the 1878 Berlin treaty, introduced new international values of minority rights and freedom of religious expression into the administration of Islamic endowments in first quarter of the twentieth century. By way of providing a case-study, I focus on the legal battles between Ottoman, Egyptian, Greek, Bulgarian, and Great Power representatives over the endowments belonging to the Khedival family of Egypt in the Greek Island of Thasos and the town of Kavala. Scholarship on Waqf in the era of European colonial encroachment focuses primarily on the period of the nineteenth century, when various Muslim state reformers - Ottoman, Egypt, and Indian - were influenced by Western European notions of a dichotomy between a public, secular realm and its private, religious counterpart. Under this dichotomy, according to this historiography, the administration of Waqf property was delegated to the private, religious realm of personal status or family law. I build on this literature to show, on the one hand, how this dichotomy was incorporated into the language of minority rights and freedom of religious expression in the treaty of Athens in 1913, which ceded Kavala and Thasos to the Greek government after the 1912-13 Balkan War. I argue that Greek and Ottoman diplomats, in their negotiation with their European and Egyptian counterparts, attempted to redefine the Egyptian endowments in Kavala and Thasos as 'private' Waqf (Wakf Ghayr Sahih), in order to contain Khedival sovereignty, which already overlapped with Greek and Ottoman sovereignties over the site of the Waqf. On the other hand, I also also look at the everyday administration of the Khedival waqfs in Kavala and Thasos, using the collection of Khedive Abbas Hilmi's (r.1892-1914) papers, which contain letters, reports, and petitions from agents and beneficiaries of the waqf. These documents show how the administrators of the endowment, in their attempt to maintain the waqf’s financial integrity in the face of mass deportation and relocation of population groups, borrowed the language of treaty regimes to reclassify the beneficiaries into refugees and clients.