_Coercitio_ implies summary jurisdiction; and the infliction of fines beyond a certain limit, scourging, or death subjected a magistrate to the _provocatio_, and therefore made him a partner in a trial before a popular assembly. Hence the judicial power of the tribune, also a necessary consequence of his power of veto. Undoubtedly when the office was created this consequence was not foreseen. When it was found to be a necessary accompaniment of the tribunician power, tradition tells us that it was questioned by the Patricians. The historically worthless but typical trial of C. Marcius Coriolanus in 491 B.C. elicited a protest that the _jus_ of the tribunes extended only to Plebeians.[366] The protest was idle, for the _jus auxilii_ could not exist without the _jus poenae_ against its violators. The violation of plebeian rights which was thus met by tribunician coercion and jurisdiction, was always an infringement of the safety or dignity of the tribune himself. Even the infliction of wrong on an individual through the violation of the tribune’s decree was a wrong done to the Plebs through him; it was not held to affect the rest of the community; hence the not unnatural belief of our annalists that, when the tribune pronounced a sentence against which there was an appeal, he brought the matter before the assembly of the Plebs.
This right of reference implies the power known as the _jus agendi cum plebe_. It was a power that could not have been contemplated on the establishment of the tribunate, but it proved a necessary consequence of the _auxilium_. Its acquirement meant a new infringement of the rights of patrician magistrates; for the summoning of the Plebs meant the calling away of a large portion of the Populus from the consuls. Two summonses of two assemblies containing the same individuals by different magistrates meant an inevitable conflict of authority, and the tribunician right of transacting business with the Plebs could not be secured but by a definite guarantee against consular interference. This guarantee was given, tradition says, by a resolution of the Plebs itself, passed in 492 B.C., two years after the institution of the tribunate, under the presidency of the tribune Sp. Icilius.[367] The date is probably too early, and the resolution must have been subsequently ratified by a _lex_ of the centuries. It enacted that when the tribune addressed the Plebs no one should speak against or interrupt him; that the tribune should fine the offender and demand securities. If securities were not forthcoming, the offender should be punished with death and his property confiscated to the gods. If the fine were disputed the judgment should rest with the people. Whether by “people” here was meant Populus or Plebs, it was doubtless on this law that the plebeian assembly based its jurisdiction in the case of injury or insult being offered to its magistrate.