One of the most important surviving Roman documents is the lex de imperio vespasiani which was used to grant emperor's powers to Vespasian. It carries the words lex which suggests it was made statutory by an assembly, yet it is suspected that it is a Senatorial decree - consultum - that has been made into law.

The English translation of the lex de imperio vespasiani:

. . . or it shall be lawful for him to make a treaty with whom he wishes, just as it was lawful for the deified Augustus, for Tiberius Julius Caesar Augustus, and for Tiberius Claudius Caesar Augustus Germanicus;

And that it shall be lawful for him to hold a session of the Senate, to make a motion in it, to refer a matter to it, to propose decrees of the Senate by a motion and by calling for a vote by division, just as it was lawful for the deified Augustus, for Tiberius Julius Caesar Augustus, for Tiberius Claudius Caesar Augustus Germanicus;

The last paragraph is consistent with Tribunacian powers. The Tribune was originally a plebian constitutional position created so the Assemblies would have a magistrate position capable of holding a session of the Senate, making plebian legislation, and being able to veto the Senate, Assemblies or Consuls. Augustus made the Tribunacian powers the center of his imperatum, making himself Tribune for life. Future emperors started dating their reign from when they received Tribune powers.

And that, when a session of the Senate is held in accordance with his pleasure or authority or order or mandate or in his presence, the authority of all proceedings therein shall be maintained and shall be observed, just as if that session of the Senate had been announced and was held in accordance with a statute;

And that whatsoever persons seeking a magistracy, power, imperium, or charge of anything he commends to the Roman Senate and people and to whomsoever he gives or promises his electoral support special consideration of them shall be taken in every election;

And that it shall be lawful for him to advance and to extend the boundaries of the pomerium whenever he considers it to be in accordance with the public interest, just as it was lawful for Tiberius Claudius Caesar Augustus Germanicus;

And that whatever he considers to be in accordance with the public advantage and the dignity of divine and human and public and private interests he shall have the right and the power to do and to execute, just as had the deified Augustus and Tiberius Julius Caesar Augustus and Tiberius Claudius Caesar Augustus Germanicus;

Much of that is the Senate abrogating its responsibilities, but you can also see the emperor's powers cutting into the aedileships and crossing both human and divine law. Which had been separated out to a fair extent in the Roman Republic. Though a Tribune's sacriato meant that violence could not be done to a Tribune without defying divine law. They were essentially sacred.

And that by whatever laws or plebiscites it has been recorded that the deified Augustus or Tiberius Julius Caesar Augustus and Tiberius Claudius Caesar Augustus Germanicus were not bound, from these laws and plebiscites Emperor Caesar Vespasian shall be exempt ; and whatsoever things it was proper for the deified Augustus or Tiberius Julius Caesar Augustus or Tiberius Claudius Caesar Augustus Germanicus to do in accordance with any law or proposed law, it shall be lawful for Emperor Caesar Vespasian Augustus to do all these things ;

And that whatever before the passage of this law has been done, executed, decreed, ordered by Emperor Caesar Vespasian Augustus or by anyone at his order or mandate, these things shall be legal and valid, just as if they had been done by the order of the people or of the plebs.

Sanction

If anyone has done or does anything in consequence of this law contrary to statutes or bills or plebiscites or decrees of the Senate, or if he does not do in consequence of this law what it is proper for him to do in accordance with statute or bill or plebiscite or decree of the Senate, this shall not be to his prejudice nor shall he be liable to pay the people anything on this account, nor shall anyone have the right to an action or a judgment concerning this matter, nor shall anyone allow an action concerning this matter to be pleaded before him.

When Caesar made himself dictator for life, and it must be remembered a dictator was a valid Roman constitutional position, he offended the ruling oligarchs of the Senate. Who killed him - in the Senate.

Augustus was smarter and did not offend the oligarchic families so easily. He stopped taking successive consulships, as this was a means for aspiring young public figures to establish their political and public bona-fides through martial success. The Tribune for life gave Augustus the permanent magistracy he needed while still have the constitutional powers to call upon and veto the Senate and Assemblies.

By the time of Vespasian, the constitutional mechanisms for imperial power were well established, and decrees from the Senate, such as this, were sufficient to create the next emperor. By Vespasian's time, policy came from the emperor and the other constitutional bodies followed that policy, unlike during the republic, when the Senate, Assemblies, Consuls and other magistracies were far more independent policy wise.

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.

The democratic component of the Roman Constitution had been in decay for quite a while. Apparently by the end of the first century AD, the assemblies were no longer being convened in order to pass law. Senatorial decrees were filling that function, even though the Roman Constitution had the Senate as a customary body who had no statutorial power.

It seems by Hadrianic times, the Senatorial decrees had the force of law. Colin Wells' writes:

... but some modern scholars credit him [Hadrian] with the initiative in giving senatorial decrees force of law. The first such decree which we know to have directly altered the civil law is in fact Hadrianic, but there may have been earlier ones, and the distinction is perhaps important only to the specialist in legal history.

The emperor rather than a vehicle for policy, and having the other components of the Roman Constitution complete the legal basis for those policies, was now undoubtedly sovereign. Hadrian's edicts and enactments had the full force of law as well.

In the Middle Republic the Roman Constitution was richer in its magistracy and assemblic bodies. There were the Consuls who acted as military and executive power, the oligarchic body of the Senate, the three assemblies, and the Tribunes who represented popular will through enacting law and the veto.

The magistracies were elected and the democratic bodies were composed of tribal, militaristic and popular forms.

With Hadrian's reign, the assemblies are no longer convened, he was appointed through dynastic means, and he held Tribune power for life. The Consuls still exist, but the legislative power is now in the Senate, an appointed body who has tenure for life unless removed by a Censor - a position which the emperors had also adopted.

This is a big change in where the sovereignty lies in the Constitution over the space of a century. Cicero would still recognise the structures, but would be aghast at where the real power in the constitution now was.

The Early Roman Republic, while adopting the forms that were present in Regal Rome, appeared to have a genuine fear of tyranny. Vetoes were absolute, and only was was required to scuttle any legislation.

The Roman Constitution was unwritten, and did change, most often through emergency. For instance the position of Tribune was established in response to a civil emergency.

This is the weakness in the unwritten constitution; emergencies tend to have a negative effect, and in the case of the late republic, the body the constitution relied on to enforce and remember custom, were wiped out in the civil emergencies and wars of the Caesars.

Tacitus commented in The Histories that by Nero's time, there was no-one left in the Senate who knew what a republic was like.

Of the twenty-six great patrician genus or clans that dominated the Senate when Augustus ascended to imperatur, only six of them remained with Senate appointments in Hadrian's reign.

The Senate had served as an genus based oligarchic memory of Roman constitutional custom and convention. It was a pretty closed shop, Cicero, as a 'new man' was an exception even in the Late Republic.

Between the proscriptions and series of Civil Wars that constitutional memory was lost, the desire for civil order at the end of civil emergency meant that the constitution expanded again, this time with the tribunicia potestus or tribune for life. This was to become the basis of an emperor's executive, legislative and constitutional power.

The noble description of the killing of Julius Caesar in the Senate is that his claiming dictator for life was an affront to the custom and convention of the Roman Constitution. Previously dictators were temporary positions of emergency, lasting no more than six months.

A less noble reading of the murder of Caesar is that his dictator potestus or dictator for life was a direct threat to the executive, judicial and policy making power of the Senate.

This was true, Augustus found a different means to become the dominant political power - imperium maius. By Hadrian's time as emperor the assemblies were not used, Tribunes were not elected, and the Consuls were not powerful outside of military command.

In fact, the pro-consuls often had more power in the Roman Empire as the legions in the provinces could lead to them becoming the next emperor. A-la Vespasian.

x-posted

Charles Van Doren writes in A History of Knowledge that the period from 450 to 550 AD were the darkest in the history of western civilization. The Byzantine Empire was unable to re-establish the Pax Romana that western Europe had known and the literacy, commerce and law became scarce.

Instead people were illiterate, their world shrunken to a small area around where they were born. Roads were too dangerous to travel as the law was one of arbitrary violence and force. Commerce shrunk to subsistence living and barter become the main mechanism of trade as the coins of the old Roman Empire were used up. The arts, philosophy and other leisure activities that the stability of the Roman political system had enabled was gone too. The population waned as a result of this instability. Van Doren writes:

It is hard to imagine them [these years]. Historically, they are almost a blank, we only know that at the end of this period of rapine and death the region now called Europe was utterly changed.

Van Doren's argument as to why there was a fall into the Dark Ages when Europe has survived political collapse and invasions (barbarian and nation-state) since without the catastrophic collapse of society, commerce and civilization; is that it was the effect of Christianity and its cultural dominance that led to the Dark Ages.

Van Doren writes that Rome was more like we are today; deeply devoted to the material world, and with out lust for adventure, travel, power, wealth and leisure - including exercise and health. With the collapse of the Empire and its replacement by the arbitrary nature of Dark Ages feudalism, Van Doren argues the people embraced Augustine's City of God rather than Rome's City of Man. Van Doren writes:

The new kind of Christians, after the fall, had little interest in their bodies as such. They cared about the health of their souls. They had no interest in consumption. They could lose their reputation rather than gain it for possessing wealth in a society where poverty was next to godliness.

Roman wealth was replaced by Christian poverty. Van Doren notes that rationality is perfectly logical to the people living under it at the time. To a Dark Ages christian they did not see the Dark Ages as a fall, or as dark; they saw it perfectly rational and normal to devote their lives to their soul's ascent to heaven through living for God.

In the late Roman Empire there was constant difficulty in raising sufficient troops. Like the high standards of the AIF in WWI, the Roman limits to military service changed with need. Emperor Valens passed laws stopping land owners substituting homeless men for able bodied men. But there were also laws passed to stop draft dodging. Pat Southern writes:

First of all, it was declared illegal for recruits to cut off their fingers or thumbs. The repitition of such laws show they [emperors] were unable to stop the practice.

Valentinian passed laws apparently that would burn at the stake draft dodgers who mutilated themselves. Theodosius dealt with it by allowing thumbless soldiers to still serve.