Like the Spanish administrators of the American territories, English administrators of Ireland attempted to impose their own native legal system on the Irish inhabitants. Nonetheless, important differences existed between the two kingdoms' legal approaches to their respective colonial contexts. Because Spanish jurisprudence was allied with universalist Catholic doctrine and was officially based on Justinian's Corpus Iuris Civilis (the ancient Roman legal code which had close affinities to natural law discourse), Spanish administrators expected New World inhabitants to accept what they considered to be the values that were inherent in Spanish law.1 In contrast English common law had its roots not in natural law but in the peculiar customs of the English people. Thus, while the Spanish were able to claim that they were replacing unnatural Indian customs with a legal system rooted in universal natural law, the English were attempting to reform what they considered to be the unnatural practices of the Irish by imposing a legal system defined by its insularity and its peculiar affinity with English institutions.2 In this essay I show that Renaissance ethnographies on Ireland by such English administrators of Ireland as Edmund Spenser, Sir John Davies, and Fynes Moryson are fractured by a conflict between a commitment to natural-law theory, which had its origin in continental writings, and a corresponding commitment to the native English tradition of common law. I examine how works by Spenser, Davies, and Moryson dealt with this conflict within their collective project of articulating a legal justification and strategy for the pacification of Ireland.Despite reports throughout Europe of Spanish-perpetrated cruelty throughout the Americas, the idea that war or conquest could be just or even charitable when prosecuted against oppression originated within the Catholic tradition of scholastic just-war theory.3 Many of the sixteenth-century writers who were writing about war and conquest in legal or ethical terms were Spanish or continental theologians who had attempted to evaluate Spanish imperial policy in the New World. On the one side were such figures as the Scottish theologian John Major and Spanish historian Juan Gines de Sepulveda, both of whom had justified Spanish conquest and treatment of the Indians using arguments based on the foundation of natural law.4 On the other side were those who had, on similar terms, voiced criticisms of the which Spanish forces were inflicting on the Indians. Francisco de Vitoria and Bartolome de las Casas were certainly the most notable Spanish writers who favored more ethical treatment of New World inhabitants.5 Other prominent defenders of Indian rights were Domingo de Soto and Melchor Cano.6 Whether directly or through intermediaries, the ideas of many of these writers permeated the ideological fabric of England.Sir Fulke Greville's famous statement about Sir Philip Sidney's goal of fostering alliances with New World inhabitants in order to overthrow the Spanish authorities included an awareness of the inhuman cruelties of the Spanish forces, an awareness that probably originated in the English translation of Las Casas 's Brevissima relation de la destrucyion de las Indias (1552).7 Beyond this significant text, however, there were others. One important book that captured the ideas of the early Spanish debates on the ethics and justice of the New World conquests was Antonio de Guevara's Relax de principes (1529), a work twice translated into English during the sixteenth century.8 The third book of the Relax de principes, which treats the princely virtues of justice, peace, and magnificence, contains several sections that together constitute a polemic against violent imperialism and unjust conquest. In one notable episode Guevara employs the example of ancient Roman imperialism to produce a veiled critique of the injustices which Spain had committed against New World polities. …