Focusing on the formation of ius during the Principate, this volume investigates how imperial power reshaped Roman legal tradition through the institutionalization of authority. It analyzes the dynamic interaction between emperors—most notably Augustus and Tiberius—and jurists, highlighting the evolution of legal instruments such as fideicommissa and codicils. By examining specific historical cases, including the legacies of Lucius Lentulus and Vedius Pollio, the work reveals the gradual transition of legal practice from the private sphere into the public realm. Central to the inquiry is the concept of imperial auctoritas, framed as an indispensable mediating force that redefined the boundary between leges and iura. Ultimately, the study demonstrates how the consolidation of princeps-led intervention transformed legal knowledge and collective memory, establishing a controlled framework to restore, standardize, and enforce the law.