Is He not the one who governs justice?

¹⁶ “If you have understanding, hear this;
    listen to what I say.
¹⁷ Can someone who hates justice govern?
    Will you condemn the just and mighty One?
¹⁸ Is he not the One who says to kings, ‘You are worthless,’
    and to nobles, ‘You are wicked,’
¹⁹ who shows no partiality to princes
    and does not favor the rich over the poor,
    for they are all the work of his hands?
²⁰ They die in an instant, in the middle of the night;
    the people are shaken and they pass away;
    the mighty are removed without human hand.

 How could Job say God is unjust when we see Him governing justice? God was the one who administer justice to those who "think they are above the law", like kings and queens. He judged each with partiality. He does not favour the rich nor the poor. He is objective in his judgment. He removes people, judges people without us interfering. Neither can we interfere God's work. Our God is sovereign. If we know that is true, how can God be unjust in judging Job? God is impartial and He is good regardless of the situation. He is only wanted people to gain some spiritual benefit in the process, whatever the process is. In this case, it is Job going to another level in his relationship with God.