The following is an extract from 1.2.2 of Justinian’s Digest (translation by the late Professor Alan Watson), itself an excerpt from another work known as the Enchiridion, authored by Sextus Pomponius, a jurist of the 2d century A.D. In the extract below, Pomponius traces the development of the authority of the Senate and magistrates, and eventually the authority of the Emperor. It is very much an open question, of course, to what extent the sketchy and highly stylized narrative Pomponius offers is historically accurate, but the interest of the passage from the lawyer’s perspective is the interpretive and justificatory account that it offers of the development of Roman institutions, not its historical accuracy from an external and scientific perspective.
The Latin text can be found here. For a paper of mine called “The Many and the Few,” which discusses the constitutional issues raised in the passage, with connections to delegation and other problems of American law, see here.
8. [I]t came to pass that the plebs fell at odds with the members of the senatorial class and seceded and set up laws for itself, which laws are called plebiscites. Soon after the plebs had been wheedled back, because these plebiscites were giving rise to many disputes, the decision was made in the lex Hortensia that they were to be deemed to have the force of statutes. And so it came about that although there was a difference as to the method of passing plebiscites and leges (statutes), they had the same legal force.
9. Next, because it grew hard for the plebs to assemble, and to be sure much harder for the entire citizenry to assemble, being now such a vast crowd of men, the very necessity of the case imposed upon the senate trusteeship of the commonwealth. And thus did the senate come to exercise authority, and whatever it resolved upon was respected, and such a law was called a senatus consultum (senate resolution).
10. At the same time, the magistrates also were settling matters of legal right, and in order to let the citizens know and allow for the jurisdiction which each magistrate would be exercising over any given matter, they took to publishing edicts. These edicts, in the case of the praetors, constituted the jus honorarium (honorary law): "honorary" is the term used, because the law in question had come from the high honor of praetorian office.
11. Most recently, just as there was seen to have been a transition toward fewer ways of establishing law, a transition effected by stages under dictation of circumstances, it has come about that affairs of state have had to be entrusted to one man (for the senate had been unable latterly to govern all the provinces honestly). An emperor, therefore, having been appointed, to him was given the right that what he had decided be deemed law.
12. Thus, in our state either it is laid down by law, that is by statute; or there is our own jus civile, which is grounded without formal writing in nothing more than interpretation by learned jurists; or there are statutory actions-at-law, which govern forms of process; or there is plebiscite law, which is settled without the advice and consent of the senate; or there is a magisterial edict, whence honorary law derives; or there is a senatus consultum which is brought in without statutory authority solely on the decision of the senate; or there is an imperial enactment (constitutio), the principle being that what the emperor himself has decided is to be observed as having statutory force.