Andrew Lintott explores the constitutional methods open to the Roman system where laws passed by violence could be over-turned by Senatorial veto. For instance if the Assemblies were under the sway of violence they would be unable to replace, modify or pass new laws to remove the bad laws that had been made under coercion.

Prior to the late republic, laws were not passed under the Roman Constitution that were repugnant to the Senate (the optimates). It was only in the later republic when the constitutional mechanisms, such as Tribunes, were in place to challenge the constitutional primacy of the Senate. Lintott writes:

Annulment was essentially a political weapon of the optimates reviving as it did the patrum auctoritas in a new form.

He argues that this was intended to be used as a mechanism to stave off the passing of laws by violence because there was no statute offense against violence itself being used in this manner - a failing of the Roman Constitution in Lintott's view. The opening it allowed however, was political, and for the Senate as a social class, to use against plebian policies and demogogic leaders. Lintott continues:

At times when the authority of the Senate was strong this did not matter: at other times the evasion by the optimates of a direct challenge to violent legislation allowed an escape route to unscrupulous politicians and, indeed, was an encouragement to violence.

Central to Lintott's thesis on the Roman Constitution and the increasing violence in the late republic is that violence was not only tolerated as part of the constitutional system it was seen as a legitimate mechanism for securing redress; privately, publicly and politically.

Rome started as a monarchy and grew different constitutional elements over the centuries that it operated as a republic. When it became an Empire under Augustus Caesar the republican elements were co-opted into the politics and constitutional machinery of an emperor.

The constitution of the middle and late republic contained the permanent body of the Senate which was oligarchic. The elected elements were the consuls and the tribunes. The consuls were more like generals even though they had the absolute power of imperium. The Tribunes represented the plebians and could veto Consul's and Senatorial legislation.

There were numerous other constitutional positions and magistracies; but Rome did not contain anything that we would call a police force or sheriffs. As a consequence there was a great deal of tradition surrounding dealing with theives and other forms of property and personal violence which involved the gathering of neighborhood help, that served as a local vigilante group or gang. This is a greatly different society to the liberal democracies we know today with their ample public services.

Even so the Roman Republic managed to sustain itself in a relatively similar manner, with and without external pressures, until violence rose to the surface almost continually in the last century of the republic. Andrew Lintott writes:

The constitution that evolved [in Rome] was more of a truce position than a peace settlement. It formalized the conflict between the oligarchic element and the plebs. Afterwards in the period of concordia the tribunes from time to time tested the authority of the consuls and their own powers. In a conflict the Senate was usually accepted as the referee, but otherwise the rules of the game made a decision impossible, and the end was resignation or stalemate.

Lintott identifies the constitution as being unable to produce a form of power sharing that was suitable enough to dampen political violence and keep it from spilling over into civil war. Gangs were a constant presence in the last century and were founded in the use of force for private violence. Once gang warfare grew above a certain level it required military intervention or violence on the scale of military force to be put down. Ultimately that became part of politics and civil war was how power was bartered between competing factions.

From 133 BC there was a progressive loss of scruple and restraint, as violence bred violence, but there had been an inherent weakness in Roman society, which was vulnerable to circumstance.

The constitution was unequal to controlling violence.

At the same time its [violence's] use was encouraged both by tradition and principle, and politicians applied these without foreseeing the consequences.

The end result was Augustus Caesar establishing himself as emperor through Tribunacion powers. The constitution moved in such a form that violence was dampened by the absolute political power of Augustus. However, it was no longer of the republican form that Cicero saw as the perfect government, and Rome survived centuries more as an Empire.

Hadrian is best known in Australia through Hadrian's wall in England which separated the Romans from the Celts of Scotland. Publius Aelius Hadrianus was the emperor of Rome between 117 and 138 AD. The emperors had been constantly changing the unwritten Roman Constitution in such a way to increase their power; by 138 AD there was no doubt that the emperor was sovereign. (more)

Rome did not have a written constitution as the United States or Australia do. It did not even appear to have a Westminster style one such as Britain's or Tasmania's which exists across multiple non-contiguous acts. It seems to be purely a mix of convention and tradition. Which was probably why it was easy for Sulla, Caesar and Augustus to subvert it. (more)