Staring in the late sixteenth century, as the sea became increasingly dangerous for Ottoman merchants and travelers, and as the Ottoman navy’s mastery of it became an increasingly distant memory, the chief jurists of the Ottoman Empire, the ?eyhülislams, responded to the challenges of rising maritime violence with a novel body of legal opinions (fatwas) that developed progressively in complexity and specificity. Lacking any tradition of maritime law in the Hanafi jurisprudential canon, late sixteenth and seventeenth-century ?eyhülislams used fatwas, later compiled and disseminated through fatwa collections, to chart a new course through murky legal waters. United by a concern with the boundary between the Abode of Islam (darülislam) and the Abode of War (darülharb) and its crossing, these maritime fatwas helped to clarify what those terms meant for a sea without borders; they compartmentalized acts of raiding and seizure that led to ownership disputes over ships and slaves into those where a previous owner could reclaim his property and those where he could not, taking into account the particularities of early modern Mediterranean commercial practices; they reinforced the Ottoman Islamic understanding of Ottoman subjecthood as inherently voluntary and contingent on obedience, but unaffected by involuntary or authorized travel by sea or to the darülharb; and they drew the line between acceptable and unacceptable raiding practices, underlining the necessity of sultanic approval and the sultan’s role as the gatekeeper of holy war. In their original issue, the fatwas discussed in this paper were often intended to support a particular side in lawsuits or to bolster sultanic edicts. In their collected form, I argue, the maritime fatwas were meant to provide authoritative guidance and comprised a new body of Ottoman maritime law.