Over the last decade of the nineteenth century, British patrol ships in the Western Indian Ocean encountered a recurring problem. Dhows from the small port of Sur, in southern Oman, would raise the French flag whenever they were approached by British gunboats or present naval officers with papers declaring them to be French protégés. Their actions raised concern in official circles, as the Suri dhows were often suspected of transporting slaves. By the beginning of the twentieth century, the government of Great Britain brought the French government before the Permanent Court of Arbitration at The Hague, where the parties grappled over whether the French consul had the right to grant flags and passes to Suri dhows. The case became foundational to studies of the law of the sea, and the ruling is still cited in footnotes in law school textbooks today. Buried in the case’s proceedings, however, are materials that give historians a window into the legal imaginaries of Indian Ocean mariners in an age of empire. In statements collected by different consuls, Suri mariners revealed how they saw their place in a world of empires and regulations, how they understood imperial law to manifest itself in artifacts like flags and passes, and how they articulated claims to particular rights as members of a trans-oceanic community of sailors with property and kinship ties to French possessions around the Indian Ocean. This paper draws from material in England, France, Zanzibar, and Oman to chart out the multiple understandings of international law that animated the proceedings in Muscat Dhows case. It focuses on the claims made by the dhow captains and mariners themselves, and how they drew on the language and artifacts of imperial political economy in order to domesticate it. Suri mariners used particular words and phrases to locate themselves within an imperial legal geography, and appropriated legal technologies – passes and flags – to help them navigate an oceanic space marked by increasingly cumbersome regulations. The claims they articulated and the practices they engaged in at sea illuminate a maritime commercial and legal culture at work – one animated by a long history of encountering regional and global empires at sea. The documentary practices they engaged in shed light on how they engaged in and venacularized a body of international and imperial law, illustrating how a regulatory regime manifested itself in an oceanic commercial arena that already ran thick with legal idioms.