When nothing else would cause them to heed him and they were unconcerned by the fact that the trial had been held in a manner contrary to custom, he ran up to the Janiculum before they took any vote at all, and pulled down the military flag, so that it was no longer lawful for them to reach a decision.
28 1 Now this matter of the flag is as follows. In ancient times there were many enemies dwelling near the city, and the Romans, fearing that while they were holding a centuriate assembly by centuries foes might occupy the Janiculum and attack the city, decided that not all should vote at once, but that some men under arms should by turns always guard that position. 2 So they guarded it as long as the assembly lasted, but when this was about to be adjourned, the flag was pulled down and the guards departed; for no further business could be transacted when the post was not guarded. 3 This practice was observed only in the case of the centuriate assemblies, for these were held outside the wall and all who bore arms were obliged to attend them. Even to this day it is done as a matter of form.
So on that occasion, when the signal was pulled down, the assembly was adjourned and Rabirius was saved. Labienus, indeed, had the right to bring suit again, but he did not do so. (Dio 37.27.3-28.4)
In the spirit of using the blog to dump little bits of information I might want later, here is a passage on the procedure of the centuriate assembly. It provides a nice parallel to narratives of Bibulus “watching the skies” to annul Caesar’s legislation during their join consulship (59BC). It illustrates ritualized militarism. AND, it has a nice allusion to later practice. Dio is writing in the high empire as a senator under the Severan emperors and he reports: “Even to this day it is done as a matter of form”. It also makes me think about the function of the filibuster in the US legislative process. Although, the context of the passage is actually a political trial in 63BC, not a legislative process. The Senate can be used for certain trials under the US constitution as well.
As an aside, I enjoy how Dio transitions from a discussion of Rullus’ popular legislation to a reflection on what it means to prosecute the 36 year old crime of killing Saturninus thus explicitly connecting the two sets of tribunician legislation.