Why do Korean judgments use Chinese characters?

Because Korea didn't have its own characters at the earliest, it was written in Chinese, so the law book you read is in Chinese.

Japanese characters are still mixed with Chinese characters, and there are also Chinese characters that they have modified at will. But since ancient times, Japan has escaped the fate of being ruled by the Han nationality because of the ocean. Never subordinate to China. At present, there are no Chinese characters in Korean, and only a few laws and ancient books are written in Chinese characters, because legal books need to be rigorous, ancient books are abstruse, and Korean cannot be accurately expressed. From the Qin Dynasty to the Qing Dynasty, the Korean Peninsula belonged to China until the Japanese invasion.

In the past, South Korea used Chinese characters, so some of their laws were also written in Chinese characters, such as some principles.