Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Throwing Open of Marriage and of Magistracies - Military Tribunes with Consular Powers
Nothing shows so clearly the defencelessness of the clan-nobility when opposed to the united plebs, as the fact that the fundamental principle of the exclusive party--the invalidity of marriage between patricians and plebeians--fell at the first blow scarcely four years after the decemviral revolution. In the year 309 it was enacted by the Canuleian plebiscite, that a marriage between a patrician and a plebeian should be valid as a true Roman marriage, and that the children begotten of such a marriage should follow the rank of the father. At the same time it was further carried that, in place of consuls, military tribunes--of these there were at that time, before the division of the army into legions, six, and the number of these magistrates was adjusted accordingly-with consular powers(1) and consular duration of office should be elected by the centuries.
1. The hypothesis that legally the full -imperium- belonged to the patrician, and only the military -imperium- to the plebeian, consular tribunes, not only provokes various questions to which there is no answer--as to the course followed, for example, in the event of the election falling, as was by law quite possible, wholly on plebeians --but specially conflicts with the fundamental principle of Roman constitutional law, that the -imperium-, that is to say, the right of commanding the burgess in name of the community, was functionally indivisible and capable of no other limitation at all than a territorial one.
There was a province of urban law and a province of military law, in the latter of which the -provocatio- and other regulations of urban law were not applicable; there were magistrates, such as the proconsuls, who were empowered to discharge functions simply in the latter; but there were, in the strict sense of law, no magistrates with merely jurisdictional, as there were none with merely military, -imperium-. The proconsul was in his province, just like the consul, at once commander-in-chief and supreme judge, and was entitled to send to trial actions not only between non-burgesses and soldiers, but also between one burgess and another.
Even when, on the institution of the praetorship, the idea rose of apportioning special functions to the -magistratus maiores-, this division of powers had more of a practical than of a strictly legal force; the -praetor urbanus- was primarily indeed the supreme judge, but he could also convoke the centuries, at least for certain cases, and could command an army; the consul in the city held primarily the supreme administration and the supreme command, but he too acted as a judge in cases of emancipation and adoption--the functional indivisibility of the supreme magistracy was therefore, even in these instances, very strictly adhered to on both sides.
Thus the military as well as jurisdictional authority, or, laying aside these abstractions foreign to the Roman law of this period, the absolute magisterial power, must have virtually pertained to the plebeian consular tribunes as well as to the patrician. But it may well be, as Becker supposes (Handb. ii. 2, 137), that, for the same reasons, for which at a subsequent period there was placed alongside of the consulship common to both orders the praetorship actually reserved for a considerable time for the patricians, even during the consular tribunate the plebeian members of the college were -de facto- kept aloof from jurisdiction, and so far the consular tribunate prepared the way for the subsequent actual division of jurisdiction between consuls and praetors.
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