The legal problem that Justinian the Great faced when he became emperor was:
**Option 3: Many laws contradicted each other, and several were no longer relevant to society.**
Justinian realized that there was a need to codify and revise the existing Roman laws, as many of them had become outdated, contradictory, and no longer suited the evolving society of his time. This led to his efforts to create a comprehensive and organized legal code known as the "Corpus Juris Civilis" or the "Justinian Code," which aimed to streamline and clarify the Roman legal system.