Recent studies on the relationship between the Ottoman kanun and the sharī‘a have emphasized the sultan’s ability to intervene in Hanafi fiqh, canonizing it and qualifying its application. However, the reigning perception in the field remains that the kanun did not substantially change any points of Hanafi doctrine. My paper will enhance our understanding of Ottoman legal practice by demonstrating a critical way in which the kanun did in fact revise Ottoman Hanafi doctrine. Additionally, I will show that the person most responsible for fomenting this change in Hanafi doctrine was none other than Mehmed Birgevi, a scholar famous for his conservatism and a most unlikely proponent of innovative change. Unlike the other Sunni schools, pre-Ottoman Hanafism rejected that the sultan could conquer a land and immediately proclaim it as property of the treasury, or bayt al-mal. By the mid-sixteenth century, Ottoman Hanafis took the position that the land was, for the most part, owned by the bayt al-māl, but maintained that treasury ownership had resulted from a long and piecemeal historical process: the cultivator-proprietors had died, or abandoned the land, or had become unable to work it. While the Şeyhülislam Ebu’s-Su‘ud Efendi famously took the position that the sultan could claim newly conquered land immediately for the treasury, he did not provide any argument to justify it other than administrative necessity. It was Mehmed Birgevi—often believed to be an ardent critic of Ebu’s-Su‘ud’s rulings on land tenure—who not only accepted this innovation, but also went to some length to create a juridical justification for it. The position that newly conquered land would immediately fall under treasury ownership, along with Birgevi’s justification of it, came to be universally espoused by the Hanafis in the Ottoman Empire both in fatwas and academic manuals, reversing the previous doctrine of the school. This change was peculiar to Ottoman Hanafism in the early modern period, and Hanafis outside the Ottoman Empire retained the school’s previous stance. Drawing from sources in both Arabic and Ottoman Turkish, this paper is based on published texts authored by Ebu’s-Su‘ud, Mehmed Birgevi, Şeyhizade, ‘Alā’ al-Dīn Ḥaṣkafī and Ibn ‘Ābidīn. It also examines manuscript copies of the “Fetavā-yı ‘Atā’i” of the eighteenth-century Şeyhülislam Mehmed ‘Ata’ullah and Nehriyyetü’l-Fetva, a work by an eighteenth-century mufti of Erzurum.