History of the Constitution of the Roman Republic
The history of the Constitution of the Roman Republic is a study of the ancient Roman Republic that traces the progression of Roman political development from the founding of the Roman Republic in 509 BC until the founding of the Roman Empire in 27 BC. The constitutional history of the Roman Republic can be divided into five phases. The first phase began with the revolution which overthrew the Roman Kingdom in 509 BC, and the final phase ended with the revolution which overthrew the Roman Republic, and thus created the Roman Empire, in 27 BC. Throughout the history of the republic, the constitutional evolution was driven by the struggle between the aristocracy and the ordinary citizens.
Constitutio Romana
The Constitutio Romana (or “Roman Constitution”) was drawn up between King Lothair I of Italy (818–855), co-emperor with his father, Louis the Pious, since 817, and Pope Eugene II (824–827) and confirmed on 11 November 824. At the time the election of Eugene was being challenged by Zinzinnus, the candidate of the Roman populace. Eugene agreed to several concessions to imperial power in central Italy in return for receiving the military and juridical support of Lothair. The "Constitutio" was divided into nine articles. It introduced the earliest known Papal Oath, which the Pope-elect was to give to an imperial legate before receiving consecration. It also restored the custom established by Pope Stephen III in 769 whereby both the laity and clergy of Rome would participate in Papal elections.