Had his action been really illegal or not? The Valerian, Porcian, and Sempronian laws certainly enacted that no citizen should be put to death except by vote of the people, after a formal trial before them. Cicero justifies his apparent violation of these laws on two grounds—
(1) That the conspirators, having become hostes by their own act, and having been recognised as such by resolution of the Senate, had ipso facto forfeited the rights of citizens (1. §28; 4. §10).
As regards this, we may remark that, though the conduct of the conspirators might justify the adoption of active measures against them, it could not legally be held to deprive them, when arrested, of the benefit of trial. For the question, whether they had acted as hostes or not, would be exactly the point which the law-court would have to decide. The argument is, in fact, from the legal point of view, a petitio principii.
(2) That the 'ultimum decretum' of the Senate (see Introduction, page 11) invested the Consul with dictatorial powers, including the right of summary execution. (1. §4 habemus senatus consultum, etc.)
In support of this he recalls the fact that C. Gracchus (121) and Saturninus (100) had been killed by the Consuls Opimius and Marius respectively, acting under a similar decree. It is certain that a party in the Senate claimed the right of thus arming the Consul with exceptional powers in cases of emergency, and Sallust (Cat. 29) distinctly says that they possessed it. On the other hand, the right had never been admitted by the popular leaders, who had, as a protest, brought Opimius to trial for the murder of C. Gracchus, though they had not secured a conviction. They had, moreover, during this year (63) accused of murder one C. Rabirius, who had been concerned in the death of Saturninus thirty-seven years before. The trial was avowedly instituted for the purpose of contesting the right of the Senate to invest the Consul with dictatorial powers. Cicero, who defended Rabirius, claimed that the 'ultimum decretum' acquitted his client of all liability. But it seems probable that he would have been condemned, had not his supporters found means to prevent the trial from coming to a decision.
It is on this point that the question of legality or illegality really turns, and as the Romans were not themselves agreed upon it, we can scarcely pronounce a decision. If the Consul did possess dictatorial powers in virtue of the 'ultimum decretum,' then the execution was legal; if (as seems, perhaps, the more reasonable view) he did not, then it was illegal. In any case, it is clear that the Senate, as such, could not order the execution of any citizen. They could only arm the Consul, and though he was at liberty to consult them on this, as on any matter of importance, the responsibility of the particular measures taken rested with him alone.
Unconstitutional actions may, however, sometimes be justified on the ground of the necessities of the case; and Cicero might fairly plead that the executions had proved efficacious in checking the spread of the conspiracy, (a result which the measures previously taken had entirely failed to secure,) and that it was very doubtful whether, if the prisoners had been kept for trial, a general rising could have been avoided.
The position of Caesar is somewhat hard to understand. As a popular leader, he must have held the view that neither the Consul nor the Senate had the right of dealing summarily with the accused; yet by proposing the alternative punishment of imprisonment he seems to admit their jurisdiction. Possibly he took this course as the best means of saving their lives for the moment, but if so it is not clear why he should have added the provision that their property should be confiscated.
The first and fourth speeches are orationes pro senatu habitae, the second and third are contiones ad populum.