The Roman Constitution was an uncodified set of guidelines and principles passed down mainly through precedent. The Roman constitution was not formal or even official, largely unwritten and constantly evolving. Having those characteristics, it was therefore more like the British and United States common law system than a sovereign law system like the English Constitutions of Clarendon and Great Charter or the United States Constitution, even though the constitution's evolution through the years was often directed by passage of new laws and repeal of older ones.
|Precedent and law|
|Titles and honours|
Concepts that originated in the Roman constitution live on in both forms of government to this day. Examples include checks and balances, the separation of powers, vetoes, filibusters, quorum requirements, term limits, impeachments, the powers of the purse, and regularly scheduled elections. Even some lesser used modern constitutional concepts, such as the bloc voting found in the electoral college of the United States, originate from ideas found in the Roman constitution.
Over the years, the Roman constitution continuously evolved. By the late 5th century BC, the Constitution of the Roman Kingdom had given way to the Constitution of the Roman Republic. By 27 BC, the Constitution of the Roman Republic had transformed into the Constitution of the Roman Empire. By 300 AD, the Constitution of the Roman Empire had been reformed into the Constitution of the Late Roman Empire. The actual changes, however, were quite gradual. Together, these four constitutions formed four epochs in the continuous evolution of one master constitution.