This section is from the book "Popular Law Library Vol1 Introduction To The Study Of Law Legal History", by Albert H. Putney. Also see: Popular Law-Dictionary.
The old popular assemblies for a period after the establishment of the Empire still went through the form of passing acts, which had been prepared by the real governing power, but in addition to this the Emperor was given the power of direct legislation by his own authority.
Laws which owed their force to the authority of the Emperor were known as Constitutiones and may be divided into four principal classes, as follows:
1. "Edicts, which were public ordinances, of universal application throughout the Empire. These had the authority of laws, inasmuch as they were generally enforced and applied to all. In the earlier reigns they were frequently renewed, and they derived their authority from the Emperor as the praetorian edict did from the praetor. Gradually they came to be held as permanently binding the real ground of their permanent force, custom was overlooked, and the imperial authority was regarded as such ground.
2. "Decrees, which were decisions in judicial cases brought before the Emperor as final court of appeal. Inasmuch as they were interpretations of the law, they were regarded as binding upon all courts.
3. "Rescripts, which were decisions upon questions of law submitted by courts and private persons. They were closely connected with the pontificial interpretations.
4. "Mandates, which were directions to officials in the exercise of their offices. These, by repetition in the various instructions sent out from time to time by the Emperor, became a source of general law. They were theoretically in force only during the lifetime of the Emperor from whom they proceeded; but they became of permanent force because of repetition and custom." 1