To some degree the new Praetor had sufficient discretion to modify the existing Edict of the former Praetor. Praetors often did not possess any special expertise in law, but rather were successful politicians. Many years the new Praetor would simply adopt and so continue the contents of Edict he "inherited" from his predecessor.
In deciding whether or not to augment or otherwise modify the Edict, the new Praetor would usually consult with Roman jurists who were familiar with the applicable areas of the law, and who knew the emerging currents of legal change. Language from the responsa of these Roman scholars of jurisprudence often found its way into the Edict.
Changes usually resulted in welcome legal innovations. With the accretion of annual modifications, the document grew in stature, as well as in size, scope, and reach; it became a primary source of legal growth and evolution.
While a Praetor was not a legislator, so technically did not create new law when he issued his edicts (magistratuum edicta), their rulings enjoyed legal protection (actionem dare) and were in effect often the source of new legal rules. Thus, over the course of time, parallel to the civil law and supplementing and correcting it, a new body of praetoric law emerged.
Interestingly, Praetors did not have to abide by their own Edict until a lex Cornelia de edictis passed in 67 BCE which required them to do so.
Eventually, it was no longer considered appropriate that the Praetor urbanus be allowed discretion to develop his own Edict . Accordingly circa CE 129 action was taken that severely restricted its further modification. Under the emperor Hadrian (r. 117–138), the celebrated jurist Salvius Julianus1 made a formal revision to the Praetor's Edict as well as to similar edicts, e.g., that of the Aediles. This newly edited and consolidated version of the edict then became fixed, subject only to changes approved by the Emperor: hence, the Edictum perpetuum.
Subsequent jurist Papinian (c. 148–211) noted the Edict had become an instrument which could supplement, explain, and improve the Ius civile (ie Roman Law) writing -
Ius praetorium est quod praetores introduxerunt adiuvandi vel supplendi vel corrigendi iuris civilis gratia propter utilitatem publicam"
This is also called honorary law (jus honorarium), being so named for the high office (honos) of the praetor."
- ("praetoric law is that law introduced by praetors to supplement or correct civil law for public benefit").
- "Praetorian law (jus praetorium) is that which in the public interest the praetors have introduced in aid or supplementation or correction of the jus civile."
The Edictum perpetuum became the basis for extensive legal commentaries by later classical jurists like Paulus2 and Ulpian2 (both c. 170 – 223).
- Roman jurists clearly separated the legal right to use a thing (ownership) from the factual ability to use and manipulate the thing (possession). They also found the distinction between contract and tort as sources of legal obligations.
- The standard types of contract (sale, contract for work, hire, contract for services) regulated in most continental codes and the characteristics of each of these contracts were developed by Roman jurisprudence.
- The classical jurist Gaius (around 160) invented a system of private law based on the division of all material into personae (persons), res (things) and actiones (legal actions). This system was used for many centuries.
Under Theodosus II's* Law of Citations, the writings of Papinian, Paulus, Ulpian, Modestinus, and Gaius were made the primary juristic authorities who could be cited in court. Others cited by them also could be referred to, but their views had to be "informed by a comparison of manuscripts".
- emperor 408-450
1 Salvius Iulianus' principal work was his Digesta, a systematic treatise on civil and praetorian law which was often cited by Roman legal writers. “It is a comprehensive collection of responsa on real and hypothetical cases; in general, it followed the edictal system.” The works of Iulianus, in particular his Digesta, "are among the most highly appreciated products of Roman juristic literature."
... According to Prof. Buckland, his presence worked to transcend the opposing schools or sects of Roman law which had continued for several centuries. Prof. Sohm states:Julianus also wrote commentaries on works of two earlier, [now] little known jurists, Urseius Felix [Urseius, 4 books] and Minicius [Minicius, 6 books], and a booklet De ambiguitatibus [On doubtful questions]."His vast acquaintance with practical case-law, the ingenuity of his own countless decisions, his genius for bringing out, in each separate case, the general rule of law which, tersely and pithily put, strikes the mind with all the force of a brilliant aphorism and sheds its light over the whole subject around--these are the features which constitute the power of his work .." https://en.wikipedia.org/wiki/Salvius_J ... n_90_books
2 Paulus’ was one of the five jurists whose opinions were made constitutionally authoritative in 426 by Roman Emperors Theodosius II and Valentinian III. Another legacy from Paulus is the inclusion of his writings in The Digest which was written and put together by Byzantine Emperor Justinian I.
One sixth of the Corpus Juris Civilis in the Digest consists of Paulus’ work. Paulus is the most excerpted Roman jurist in the Digest. After Paulus, Ulpian is the second most excerpted Roman jurist in the Digest. The Digest attributes to Paulus the first articulation of the presumption of innocence in Roman law: Ei incumbit probatio qui dicit, non qui negat—"Proof lies on him who asserts, not on him who denies" ...
Due to Paulus' fame several other works have been attributed to him, in particular the 3rd century compilation Pauli sententiae ("Paul's Views" or "Sentences"). From Paulus’ surviving works and works attributed to him, the Sententiae ad Filium have the longest fragments.
https://en.wikipedia.org/wiki/Julius_Pa ... egal_works