In his book, al-Kawkab al-durri, the Shafi’i scholar Jamal al-Din al-Asnawi (d. 772/1370) provides a compelling case for how substantive laws (fiqh) can be extrapolated from the rules of grammar. Al-Asnawui understands Islamic law as deriving from legal theory (usul al-fiqh), but that legal theory was not formulated until the Risala of al-Shafi’i (d. 204/820). He understands, however, that substantive laws can also be extrapolated from the rules of grammar (nahw; ‘arabiyya), a project that he attributes to al-Shafi’i’s contemporary Ibn Hisham (d. 218/833). In a different book, al-Tamhid fi al-takhrij, al-Asnawi demonstrates how to extrapolate substantive laws from legal theoretical principles. This is a rather more straightforward account of the legal process as traditionally understood. Al-Asnawi wrote the books at more or less the same time, as part of a larger project, as he tells us in the Tamhid. He not only wants to understand how law and grammar overlapped in an earlier period, but even how these two disciplines overlap in what he says are the touchstone works, the Irtishaf al-darab by the Andalusi grammarian Abu Hayyan (d. 745) and the Sharh Kabir by the Cairene Shafi’i al-Rafi’I (d. 624/1226). My paper will compare the approach that al-Asnawi takes in relating substantive law to grammar and legal theory. In this way, I hope to shed light into the relationship that al-Asnawi saw between language, law, and legal theory.