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
Through this set termination of the supreme office the practical irresponsibility of the king was lost in the case of the consul. It is true that the king was always in the Roman commonwealth subject, and not superior, to the law; but, as according to the Roman view the supreme judge could not be prosecuted at his own bar, the king might doubtless have committed a crime, but there was for him no tribunal and no punishment. The consul, again, if he had committed murder or treason, was protected by his office, but only so long as it lasted; on his retirement he was liable to the ordinary penal jurisdiction like any other burgess.
To these leading changes, affecting the principles of the constitution, other restrictions were added of a subordinate and more external character, some of which nevertheless produced a deep effect The privilege of the king to have his fields tilled by task-work of the burgesses, and the special relation of clientship in which the μέτοικοι as a body must have stood to the king, ceased of themselves with the life tenure of the office.
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Reference address : https://www.ellopos.net/elpenor/rome/2-01-constitution-magistrate.asp?pg=10