Final answer:
The Corpus Juris Civilis was important during the rule of Emperor Justinian because it aimed to unify and codify Roman law. It eliminated contradictions and established a comprehensive legal system that had a significant impact on European legal systems.
Step-by-step explanation:
The Corpus Juris Civilis was important during the rule of Emperor Justinian because it was a legal reform that aimed to unify and codify Roman law. Justinian saw Roman law as a way to promote unity and control within his empire. The Corpus Juris Civilis compiled and organized existing laws, eliminating contradictions and establishing a comprehensive legal system. This legal reform had a significant impact on European legal systems and is still considered an influential source of law today.