(jus praetorium), precepts of private law developed in ancient Rome by the praetors. The Digest indicates that the praetors could confirm, supplement, or support the civil law, that is, the fundamental Roman law based on statutory law. Because of inherent formalism, civil law was unable to adapt to the rapidly developing economic relations of a slaveholding society, and thus, by the end of the republican period, praetorian law had essentially become an independent legal system.
When a praetor assumed office he issued a special edict (edictum tralaticium) to provide more protection to private property owners. The edict provided for the introduction of new claims and other procedural means that for all intents and purposes nullified obsolete laws. It remained in effect for one year. In compiling his edict, each new praetor used the most important legal principles of his predecessors.
The praetors became more active legislators in the mid-second century B.C., after the promulgation of Lex Aebutia, which gave the praetor the right during a court trial to draw up legal instructions compulsory for the judges (formulae). Praetorian law significantly reformed such institutions of private law as possession, contracts, and inheritance. Bonitarian ownership—a special form of praetorian inheritance—was created on the basis of praetorian law. After the fall of the republic, the legislative activity of the praetors conflictd with the growing power of the emperors. The development of praetorian law ceased in the second century A.D., when the jurist Salvius Julianus, on instructions from the emperor Hadrian, compiled the final text of the praetorian edict (edictum perpetuum Hadriani), a codification of praetorian law.
In the fourth and fifth centuries A.D., the systems of praetorian law and civil law grew closer together, eventually becoming one system.