The Roman Constitution was an uncodified set of guidelines and principles passed down mainly through precedent.
In the early years of the Republic, the comitia curiata was the only legislative assembly with any power.
In this regard, bills voted on (called plebiscites) were similar to modern popular referendums.
In addition, no other branch had to ratify a bill (rogatio) in order for it to become law (lex).
After the founding of the empire, the vast majority of the powers of the assemblies were transferred to the Roman Senate.
[3] The last king of Rome, Lucius Tarquinius Superbus, was overthrown following a coup d'état that was planned in the Senate.
The result was that both the popular assemblies and the executive magistrates deferred to the collective wisdom of the Senate.
The declining influence of the Senate during this era, in large part, was caused by the class struggles that had dominated the early Republic.
[dubious – discuss] The end result was the overthrow of the Republic, and the creation of the Roman Empire.
To a large degree, this demonstrates the strong cultural influence of the Senate, even during the late empire.
The institution survived the fall of the Empire in the West, and even enjoyed a modest revival as imperial power was reduced to a government of Italy only.
Under the Constitution of the Roman Republic, the "executive branch" was composed of both ordinary as well as extraordinary magistrates.
The principal extraordinary magistrate, the dictator, would be appointed upon authorization by the Senate of the Roman Republic.
The two highest ranking ordinary magistrates, the consuls and praetors, held a type of authority called imperium (Latin for "command").
The lictors would carry fasces, which consisted of a rod with an embedded axe, symbols of the coercive power of the state.
All other powers of the tribunate derived from this sacrosanctity, with two rights: intercession between magistrates and advocacy for the people.
A newly appointed dictator would usually select a deputy, known as the magister equitum ("Master of the Horse").
After 202 BC, the dictatorship fell into disuse, and during emergencies, the Senate would pass the senatus consultum ultimum ("ultimate decree of the Senate") which suspended civil government, and declared (something analogous to) martial law.
After the establishment of the Principate, the old magistracies (consuls, praetors, censors, aediles, quaestors and tribunes) lost the majority of their actual powers, effectively being reduced to municipal officers in charge of various games and holidays.
The chief executive became the unchallenged power in the state, with overwhelming dominance of the Senate, which, while it as a body gained practically all authorities formerly held by the Assemblies, also became nothing more than a rubber stamp for the emperor.