The Ottoman ?eyhülislam was the empire’s chief jurist, issuing Islamic legal opinions (fatwas) at the request of individual subjects and of the state. Given Wael Hallaq’s recent argument that there was a discernible “rule of law” in pre-modern Islamic states, and in light of current constitutional dilemmas in Egypt, Tunisia, and Turkey, the relationship between the Ottoman state and Islamic law remains vital to our understanding of Islamic legal history and of the political future of the Muslim world—but it is also surprisingly understudied. Richard Repp has suggested that the jurists were co-opted, and came simply to legitimate the sultans' orders. Colin Imber, for his part, showed the ?eyhülislams’ role in reconciling the Islamic holy law (sharia) with secular decrees (kanun). Baber Johansen, meanwhile, has argued for the role of muftis in other times and places as agents of legal change. I offer a different perspective, drawing on a diverse array of legal opinions from the central Ottoman archives. These fatwas dealt with the fraught questions surrounding captivity, as the Ottomans curbed the enslavement of enemy soldiers captured in wartime, and mandated the return of all enemy captives without ransom upon making peace. Whether it was enslaving rebels, releasing captured Russians, or adjudicating the legitimacy of foreign slaves' conversions, the Ottoman state turned to the ?eyhülislam for advice on many of the most contentious issues raised in this process. Using archival documents generated by both the Ottoman scribal service and the ?eyhülislam's office, I chart the interplay between the foreign and domestic political considerations which led the Porte to consult the ?eyhülislams, and the Islamic legal traditions upon which the ?eyhülislams drew. How faithful to the tradition were they, when apparent conflicts arose? The ?eyhülislam, I conclude, certainly could affect legal change, and he did offer powerful legitimation to political decisions—but the state also seems to have consulted the ?eyhülislam for genuine legal, ethical, and even pragmatic guidance. The ?eyhülislam, for his part, appears to have navigated between the legal tradition and the desire to afford his “client” (the sultan) maximum leeway within the law. In this, I suggest, the ?eyhülislam’s position resembled the contentious role of legal advisers in other governments—including the twenty-first century United States.