Roman law consisted of three branches: civil law, natural law, and:

Roman law consisted of three branches: civil law, natural law, and "the law of people or nation".

Roman law has a history almost as old as Rome itself. In the beginning of the republic, Roman law was held in the psyches and recollections of Rome's judges and officers. Such a framework was prime for mishandle. An officer could overlook or even change laws spontaneously, and there was no real way to address him.