The foundations of the “Republic of the Indians” in the New World rested on a legal substratum that took more solid shape in the everyday interaction between indigenous subjects and the Spanish courts. Grounded in the local cabildos of some pueblos de indios in cosmopolitan areas of late colonial Peru, a higher level of legal activism that emerged was engaged in the production of laws seeking to modify well-established imperial practices of protección originally intended to assist Indian cases in courts. This essay reconstructs the genealogy of the process of law formation based on a crucial legal campaign led by Indian leaders of El Cercado in 1735 Lima aimed at substituting Spanish protectores de naturales for indigenous ones. The long-awaited legal victory of El Cercado’s native authorities demonstrates that the “República de indios” was shaped legally from below, instead of being overdetermined by the laws emanating from Madrid or the audiencias. Strategizing for the production of a real cédula, the cabildo leaders also manipulated imperial legal history and its rhetoric of “protección” as well as operated within social networks of Indians and other allies on both sides of the Atlantic and regionally in Peru.