Senatus consultum ultimum

Senatus consultum ultimum ("final decree of the Senate" or Final Act, often abbreviated SCU), is the modern term given to a decree of the Roman Senate during the late Roman Republic that was passed in times of emergency. It expressed the opinion that to preserve the republic, an urgent threat needed countering. Although an SCU could grant rhetorical or argumentative support to the use of state power, it did not change a magistrate's legal powers or deprive a Roman citizen of his right to a trial.
The form was usually "consules darent operam ne quid detrimenti res publica caperet" or "videant consules ne quid res publica detrimenti capiat" ("let the consuls see to it that the state suffer no harm"). It was first officially decreed prior to the fall of Gaius Gracchus in 121 BC and again several other times, including during Marcus Aemilius Lepidus's march on Rome in 77 BC, the Catilinarian conspiracy in 63 BC, and before Julius Caesar crossed the Rubicon in 49 BC.
Background and term.
From around the year 500 BC, the dictatorship was the main measure of emergency power in the Roman Republic. In a "senatus consultum", the Roman Senate would authorize the consuls to nominate a dictator who received "imperium magnum", great power to act in a time of emergency (usually military) until the crisis was over (but no longer than half a year). The dictatorship marked the sole exception from the rules of collegiality and responsibility, meaning the dictator was not legally liable for official actions. This changed around the year 300 BC, when, against its very nature, the dictatorship was placed under the public "provocatio", meaning that the Plebeian Council could be called to counter-act executive actions of the dictator. As a result, the practice was altered and later dropped altogether after 202 BC.
The "senatus consultum ultimum", which replaced the dictatorship in the late 2nd century, does not have a specific name in the sources, where it is usually mentioned "by quoting what was obviously its opening advisory statements to the magistrate who had it passed". It is by that specific phrase the SCU can be traced through the years. Its short name in research literature derives from a section in Caesar's "Commentarii de Bello Civili", where he writes:
Since this is the shortest mention of the decree available, "the label [...] seems to have stuck". The actual wording of the decree was however longer, Gerhard Plaumann gives it as "de ea re ita censuere: uti [...] rem publicam defendant operamque dent "(or "videant") "ne quid res publica detrimenti capiat", having distilled this from a number of sources writing about the decree. He therefore argues that "senatus consultum de re publica defendenda" or "quasi-dictatorship" would be more fitting terms. It is the vague nature of the phrase that left the decree open for attacks over its legality. The word "ultimum" (final) does not indicate it to be the last decree passed by a senate or that it constituted an ultimatum, but rather that the decree was viewed (and for the most time used) only as a "last resort".
History.
Creation of the decree.
In reaction to the redundancy of the dictatorship, the senate party were in need of a new emergency power that would not fall under the public rights of "provocatio" and "intercessio" (or veto). The "populares" under Tiberius Gracchus had challenged the power of the senate and began with a program of land reform. Because he was a Tribune of the Plebs, the senate needed extraordinary power to stop him, since Gracchus was able to appeal his demands directly to the people and bring them into law.
133 BC: First SCU against Tiberius Gracchus.
After Tiberius Gracchus had won re-election as tribune, rumour spread he aimed at becoming king. Upon hearing this the senate was in uproar, with a majority favoring to intervene with violent measures, while one of the incumbent consuls, Publius Mucius Scaevola fought against it, doubting such a step would be constitutional. The senate nevertheless passed the "final decree". Scaevola then refused to carry out any violent steps before Gracchus and his followers resorted to violence first. To this, Gracchus' cousin, Publius Cornelius Scipio Nasica, the Pontifex Maximus, reacted by shouting "qui rem publicam salvam esse vult, me sequatur" ("let every man who wishes the republic to be safe, follow me!") and led the senators against Tiberius, who was killed in the resulting confrontation.
Some researchers, such as Golden and Lintott/Momigliano, have doubted that the example of 133 BC constitutes an SCU, since the highest magistrate, the consul, who was addressed by the decree, did not act upon it. 
Plaumann has argued that this follows the false logic that the decree would only be valid once the magistrate carries it out, while in his opinion a reluctance to abide by it is possible. Nevertheless, the murder of Tiberius Gracchus was here not covered by an SCU, even if it existed, since it was not the consul who carried it out. Chen Kefeng has pointed out that "in comparison with the later ones, [this SCU] was uncommon and in inconformity to the orthodox formula due to the un-cooperation of the highest magistrate".
Attempts to strengthen public rights against the senate.
Following the precedent set in 133, several attempts were made by people generally associated with the "populares" party to protect the public rights of "provocatio" against executive power. Following the example of the "leges Porciae" from the beginning of the century, the "lex Sempronia de capite civis", initiated by Tiberius' brother Gaius Gracchus following his election to the post of Tribune of the Plebs in 123 BC, made it impossible to carry out capital punishment only ratified by the senate. The "lex Sempronia" can be seen as a direct reaction to the fate of Tiberius Gracchus and his followers, who were tried and sentenced in a special tribunal with powers of capital punishment.
121 BC: SCU against Gaius Gracchus.
Following Gaius Gracchus' second term in the office of Tribune of the Plebs, Lucius Opimius, a strict conservative, was elected consul, determined to oppose Gaius' proposals of land reform and the distribution of Roman citizenship to all Latin citizens. When, on the day that Opimius had planned to repeal the laws of Gaius Gracchus, one of his attendants was slain in a scuffle between the opposing camps, this gave the consul the pretext to act. The senate passed the "senatus consultum ultimum" and the next day, Opimius gathered the senators and their supporters to rid the city of Gaius Gracchus, who was killed in the subsequent battle.
As a consequence, Opimius was tried "quod indemnatos cives in carcerem coniecisset" ("for imprisoning a citizen without trial"), but was acquitted. With this legal precedent, the SCU as a measure standing above public "provocatio" entered the "mos maiorum".
100 BC: Gaius Marius acts against Saturninus.
In the year 100 BC, when Gaius Marius held his sixth consulship, his ally Lucius Appuleius Saturninus, tribune for the second time, pushed for reforms like those of the Gracchi. The senate opposed and violence broke out. The high chamber then passed the SCU and urged Marius to act, which he did to restore public order, even though he was generally allied with the "populares". Unlike Opimius, Marius decided to detain the insurrectionists in the Curia Hostilia and leave their fate up to debate. However, Saturninus and his followers were lynched by the mob.
77 BC: SCU against Lepidus.
Marcus Aemilius Lepidus, once an ally of Lucius Cornelius Sulla, was elected to the consulship in 78 BC. He then placed himself firmly in the camp of the "populares", clashing with his fellow consul Quintus Lutatius Catulus. The two camps came close to a civil war, so Lepidus was sent to administer the province of Transalpine Gaul. He returned however a year later with his army and a group of followers. The senate passed the SCU which was then acted out mainly by Catulus, now a proconsul, and Gnaeus Pompeius Magnus, not by the consuls themselves.
63 BC: Attacks on the SCU and Catilinarian conspiracy.
Trial against Rabirius.
In early 63 BC, shortly after Marcus Tullius Cicero took office as consul, Julius Caesar urged Titus Labienus, a tribune who had lost his uncle during the turmoils of 100 BC, to accuse Gaius Rabirius of participating in the murder of Saturninus and his followers. The importance of the trial is illustrated by the fact that Cicero himself, even though he was incumbent consul, decided to lead the defense for Rabirius. The trial was carried out in the obsolete form of "perduellio", with Caesar and his cousin Lucius Julius Caesar presiding. Cicero argued that even though Rabirius was a "privatus" (private man) and therefore not the addressee of the decree, he still had the duty as a Roman citizen to defend the state against its enemies, resorting to the ancient Roman principle of self-help. Labienus and Caesar argued the contrary: even if the SCU gave the power to execute capital punishment, it should only be carried out by the highest magistrates. Rabirius was convicted but escaped punishment through a ruse during the appeal before the Concilium Plebis. The authority of the decree was nevertheless shaken and in no further cases did private persons act out an SCU.
Cicero exposes the Catilinarian conspiracy.
During the year of his consulate, Cicero thwarted a conspiracy led by Lucius Sergius Catilina, aimed at overthrowing the Roman state. Equipped with the SCU that the senate had passed on October 21, Cicero held four speeches against Catiline (the Catiline Orations), driving the conspirator from the city. Catiline's supporters however started turmoil within the city while Catiline marched against it with an army. He had also tried to involve the Allobroges in his fight, but Cicero worked with the Gauls and presented Catiline's letters to them as evidence before the senate. 
While the conspirators were held prisoners, the senate went on to discuss their fate. Probably due to the experience of the trial against Rabirius, Cicero, who could have acted on his own under the authority given to him by the SCU, chose to seek broader support from his fellow senators just as Gaius Marius had done in 100 BC. After the majority of the house had spoken in favor of executing the culprits, Julius Caesar swayed many by suggesting that they should be exiled to various Italian cities until the revolt was over and they could be tried in court. He argued that executing the conspirators would break the "lex Sempronia". Here again Caesar tried to further limit the power given by the decree by putting it under the control of "provocatio" laws. Cato the Younger, speaking later, successfully convinced the house to impose the death penalty. The conspirators were then taken to the Tullianum prison and strangled. While Cicero received the honorary title "pater patriae" for his actions, which were highly popular with the public, but he feared retribution for executing Roman citizens without trial.
Cicero is exiled.
After Caesar's consulate in 59 BC, he helped Publius Clodius Pulcher into the office of tribune of the plebs before setting off into his provinces. Clodius passed a law outlawing people who had executed citizens without trial. Seeing that the consuls were unwilling to help, Cicero did not wait for a trial and fled the city into exile; Clodius then passed another law denying Cicero shelter within 400 miles of the city. Caesar's long set goal to bring the SCU back under the practice of "provocatio" seemed successful, until Cicero returned at the instigation of Pompey some 15 months later, celebrated by the people.
52 BC: SCU after the murder of Clodius Pulcher.
On 19 January 52 BC, an SCU was passed by the senate after public opinion had turned against the senators due to riots following the death of Publius Clodius Pulcher, who was murdered the day before by Titus Annius Milo when on his way back to Rome. The decree was aimed against the tribunes Q Pompeius Rufus, T Munatius Plancus and C Sallustius Crispus, allies of Clodius', who had lit his corpse on fire inside the curia, burning it to the ground. When Pompey was declared "consul sine collega" two days later, the decree was obsolete, since the imminent emergency (the riots had made elections impossible) was over.
49 BC: SCU against Caesar.
During his last years in Gaul, Caesar rightly feared the senate might put him to trial for his breaches of law while he was consul. He therefore aimed to run for consul once again without having to enter the city as a private man ("privatus"). To do this, the senate needed to allow him to run for the office in absence ("in absentia"), a matter promoted by his loyal tribune of the plebs, Gaius Scribonius Curio. Following fierce debates over the course of the year 50 BC, a minority of the senate party had symbolically handed Pompey a sword on 1 December 50, in a plea that he would raise an army to defend Rome against Caesar, should the latter attack the city when his demands were not met.
At the beginning of the new year, on 1 January 49, Curio returned to Rome from Caesar, bringing with him a letter, which Caesar's new tribunes Marcus Antonius and Lucius Cassius read aloud in the senate. Afterwards, the senate once again voted on a motion to strip Caesar of his army and have him returned to Rome, which carried. Negotiations between the two camps followed, led by Cicero, who was waiting outside the city limits for his triumph. After the negotiations had not brought a solution, the senate repeated its vote on 7 January, which was immediately met with a veto by the two tribunes. It was in this situation that the senate passed the "senatus consultum ultimum" to break the tribunes' resistance and act against Caesar, at the same time declaring him an enemy of the state ("hostis"). Being warned about the fate of their predecessors in office, the two tribunes of the plebs fled the city the same night. 
Caesar got word of the SCU on 10 January while in Ravenna, crossing the Rubicon and taking Ariminum the next day, where he met Antonius and Cassius. Here, he addressed his troops and used the tribunes as living proof to legitimise his actions, calling the SCU a "new example" ("novum exemplum") not in accordance with Roman law. He argued that not even Sulla had dared to touch the right of a tribune to cast his veto, as the senate had done now under the threat of armed violence ("armis").
Additional examples in the Roman Republic and obsolescence in the Principate.
There are several additional examples of the decree being issued during the later years of the Republic. The "Oxford Classical Dictionary" gives four more examples of the SCU: In 62 BC against Quintus Caecilius Metellus Nepos and Caesar, in 48 BC against Marcus Caelius Rufus, in 47 BC against Publius Cornelius Dolabella and in 40 BC against Quintus Salvidienus Rufus. Plaumann names the SCU of 47 BC as an exceptional case, since its addressee was Mark Antony, Caesar's "magister equitum". 
Plaumann also writes about two SCUs in 88 BC, against public disturbances which were eventually resolved by Sulla. Another SCU could have been issued in 87 BC, when the consul Gnaeus Octavius acted against his colleague Lucius Cornelius Cinna. In 43 BC, after the assassination of Julius Caesar and the beginning of hostilities between Octavian and Mark Antony, a total of four SCUs can be found in the sources, of which authors like Gerhard Plaumann, whose study on the subject is still considered canonical, can make little sense. The SCU against Salvidienus Rufus in 40 BC seems to have been a matter of pure obeisance towards the "triumviri". 
It appears that the Principate with its higher political stability rendered the use of an emergency decree such as the "senatus consultum ultimum" obsolete.
Legality.
As outlined above, representatives of the "populares" faction tried to question the validity of the decree over the entire course of its 90-year existence, without success. Among them, one of the strongest opponents was Julius Caesar, who did not put the decree into question altogether, but its ability to override the popular rights of "intercessio" and "provocatio". He was later able to use this stance as an excuse to bring about the Civil War that would bring him the dictatorship, a reminiscence of the exact institution the SCU had once replaced. 
The SCU constituted an emergency decree with which the consuls, backed by the senate, were able to "claim dictatorial force". As with the dictatorship before, no positive action necessarily followed from the passing of the decree. The SCU could however be perceived as preferable to a dictator, as it distributed power only to the highest elected officials and followed the principle of collegiality. Unlike the dictatorship, the SCU was used almost exclusively in domestic conflicts. The debate over its legality continues in the research literature. Some—like Theodor Mommsen and Andrew Lintott—follow Cicero in describing the decree as a consequence of the Roman principle of "self-help" and therefore trace its legality to the very core of the Roman constitution. 
Others, such as Kefeng have argued that it contradicts basic principles of the constitution, going so far as to say "that the emergence of the "senatus consultum ultimum" is a symbol of the decline of the traditional constitution." Wiedemann, in discussing Cicero's empowerment by an SCU against Catiline, says that by the late republic, it was "little more than a fig-leaf which those who could muster a majority in the senate used to legitimate the use of force". Flower argues that while a consul could act with leeway, they would not escape accountability, and that while too the decree never named an enemy, "the decree itself, in tone and in effect, seems to subvert the effectiveness of the existing norms of the very republican government that it purported to uphold" and saying that the use of the SCU against Gaius Gracchus and Flaccus in 121 BC set a dangerous precedent that "suggested violence as the logical and more effective alternative to political engagement, negotiation, and compromise within the parameters set by existing political norms".
Bibliography.
Sources.
Abbreviations for ancient sources follow the list given in "Der Neue Pauly." Enzyklopädie der Antike (DNP). Edited by Hubert Cancik. Metzler: Stuttgart 1996–2003 (16 volumes in 19 sub-volumes plus 3 supplement volumes). .