AbstractThe chapter begins with an examination of the ideas of discovery and jurisdiction in sixteenth-century Catholic sources, along with associated developments in theories of just war. An overture to this story includes Christopher Columbus’s El libro de las profecías (1502), in which the book of Isaiah figures prominently in his interpretation of European discovery and conquest in the Indies. An influential canon lawyer, Juan López de Palacios Rubios, defended papal authority while at the same time providing an account of Indian property rights in Libellus de insulis oceanis quas vulgus indias appelat (1512–1516). This work explains how the rules of war in Deut 20:10–12, along with other sanctions, helped to shape the notorious requerimiento, a brutal and self-contradictory legal “requirement” designed to legitimate the Spanish wars of conquest between 1513 and 1548. Bartolomé de Las Casas and Francisco de Vitoria, among others from the Salamanca School, famously derided the requerimiento. Rather than sharing no common ground, Palacios Rubios, Las Casas, and Vitoria can all be located within long-standing traditions of canon law and biblical interpretation. The famous debate between Las Casas and Juan Ginés de Sepúlveda in Valladolid (1550–1551) addressed new legal questions that arose long after the major wars of conquest, and the Lascasian arguments in this debate later influenced the Protestant reformulations of the doctrine of discovery in the seventeenth century.