This article primarily explores one of the Muslim scholarly discourses aiming to construct an Islamic governance model, harmonious with the modern state, that is intertwined with premodern Islamic traditions. It scrutinizes the reinterpretation and reconceptualization of the premodern concept of siyāsa sharʿiyya in 1920s Egypt by modernist ʿulamāʾ (religious scholars) to align with the nation state’s legal and constitutional landscapes. The study focuses on the legislative aspects of this modernized theory of siyāsa sharʿiyya and demonstrates how under this theory the state conceptually begins to play a legitimate role in defining Islamic law. Special attention is given to ʿAbd al-Wahhāb Khallāf’s (d. 1375/1956) book, al-Siyāsa al-sharʿiyya, which highlights the transformative epistemological and constitutional repercussions of this discourse. Comparative analysis is conducted with the works of premodern progenitors of the concept, such as Ibn Taymiyya (d. 728/1328) and Ibn Qayyim al-Jawziyya (d. 751/1350) and later authors who have used the concept, to identify discrepancies between premodern and modern discourses in siyāsa sharʿiyya. The study also cites practical implementations of this modernized theory through a law project proposed in Egypt in 1926 that demonstrates how the new siyāsa sharʿiyya discourse bestowed an inherent legal authority to the state to independently legislate on sharīʿa laws based on an expanded conceptualization of maṣlaḥa (public benefit).