“Contested legalities in colonial Mexico : Francisco Xavier Gamboa and the defense of Derecho Indiano” explores the legal culture of late colonial Mexico through the lens of Francisco Xavier Gamboa, the most celebrated Mexican jurist of his era. Born in Guadalajara in 1717, Gamboa practiced in the courtrooms of Mexico City, represented the merchants guild of Mexico in Madrid from 1755 to 1764, analyzed mining legislation in the 1761 Comentarios a las Ordenanzas de Minas, and served three decades as an Audiencia judge until 1794. His long career encompassed the most salient features of the legal culture of his time. The central argument of this dissertation is that the legality Gamboa embodied and defended, known to historians as Derecho Indiano, came under attack in the period of the so-called Bourbon Reforms during the reign of Charles III. Led by José de Gálvez, the visitor-general of New Spain in the 1760s and later the secretary of state for the Indies from 1776 to 1787, the crown sought to streamline the legal order in order to root out corruption, restrict local autonomy, and strengthen royal authority. Gamboa and many other experienced officials opposed this effort. They argued that the old legal order, which recognized local customs and guaranteed judicial autonomy, provided the flexibility needed to maintain the Spanish empire in America. This contest in legalities marked the emergence of a centralized state in Spanish America and the moment when the Spanish legal order began to lose its legitimacy in America. / text