In 1571 he became the first inquisitor general of New Spain (and thus the first inquisitor general in the New World). He established the Tribunal del Santo Oficio in Mexico City in 1571. As inquisitor general he required people of New Spain, from the "oidores" (members of the Audiencia), nobles and religious to the most humble members of society, to solemnly swear to defend the Catholic faith and persecute heretics "as rabid dogs and wolves, infectors of spirits and destroyers of the vineyard of Our Lord." He celebrated the first "auto-da-fé" in New Spain in 1571.