Question

Who decides what is just and unjust?

Answer 1

In court the judge decide.

Answer 2

According to the psychology, our conscience in our body decides what is just and what is unjust in accordance to us.

Unjust refers to something that is not right.

On the other hand the word just can refer to the word justice.

The just law can be referred as the code that is made by man by keeping similarity with the moral law.