This book argues that the most important and influential reform of the state was that done by the first Emperor Augustus, turning the warring Roman republic into a relatively stable empire lasting 500 years in the West, and 1500 in the East. Not only was the scope incomparable to any ancient reform before or after, but the means were also novel: Augustus used the law of the day to effect crucial aspects of the reform as a whole. The book thus explores the reform of Augustus from a legal perspective. This means that, rather than the works of historians or poets, the legal texts handed down to us through a variety of ways are central. The study thereby provides new insight into a quintessential legal model for later empires. It also places the legal structure of the Roman empire in the intellectual context of Augustus in his own time. Finally, it reconstructs a Stoic theory of state as the basis of the reform. The book will be of interest to researchers working in the areas of Roman Law, Legal History, Legal Philosophy, History of Political Theory and Classical Studies.