Since the days of the Law of the Twelve Tables, developed during the early republic, the Roman legal system was characterized by a formalism that lasted for more than 1.000 years.
Early Roman law was drawn from custom and statutes, but later during the times of the empire, the emperors asserted their authority as the ultimate source of law.
Their edicts, judgments, administrative instructions, and responses to petitions were all collected with the comments of legal scholars.
"What pleases the emperor has the force of law." As the law and scholarly commentaries on it expanded, the need grew to codify and to regularize conflicting opinions.
The basis for Roman law was the idea that the exact form, not the intention, of words or of actions produced legal consequences. Romans recognized that there are witnesses to actions and words, but not to intentions. Roman civil law allowed great flexibility in adopting new ideas or extending legal principles in the complex environment of the empire. Without replacing older laws, the Romans developed alternative procedures that allowed greater fairness.
For example, a Roman was entitled by law to make a will as he wished, but, if he did not leave his children at least 25 percent of his property, the magistrate would grant them an action to have the will declared invalid as an "irresponsible testament." Instead of simply changing the law to avoid confusion, the Romans preferred to humanize a rigid system by flexible adaptation.
It was not until much later in the 6th century AD that the emperor Justinian I, who ruled over the Byzantine Empire in the east, began to publish a comprehensive code of laws, collectively known as the Corpus Juris Civilis, but more familiarly as the Justinian Code.
The Ancient Roman law was one of the most original products from the Roman Empire!