The role of the Royal Navy in the British Atlantic world has been understood as projecting imperial military power and guarding inter-oceanic trade. However, the Royal Navy's role in the creation of a legal culture in early modern Sierra Leone revises our understanding of its multifaceted mission. Royal Navy regulations and customs implemented on warships translated into the rule of law and administration on land in the context of Sierra Leone. A common legal culture, grounded by the Royal Navy's legal practices, united the culturally diverse population in Sierra Leone: the Temne, the Black Poor from London, British abolitionists, black Nova Scotian settlers, Maroons from Jamaica, and Liberated Africans after the abolition of the slave trade in 1807. Examination of these legal dynamics over time contribute to an understanding of how the establishment of colonial law, through the Royal Navy, became formalised in Sierra Leone within the pre-colonial and early colonial period.