Psalm 89:14 Justice and judgment are the habitation of thy throne:
God is the great lawgiver since the origin of Law is His nature. Divine Law is therefore as unchangeable as God. A consequence of God being the lawgiver is justice, which also flows from His nature.
Justice involves a measurable standard by which all reasoning creatures are judged equally. This standard is eternal and unchangeable because it comes from Him, and His being is unchangeable.
Justice also involves the method by which all are judged. Justice brings order to judgment. Some say God is sovereign and can do anything. Well in a sense that’s true, but in another sense it is very inaccurate. God does what His nature inclines Him to do. And it is in His nature to be Holy and Just, therefore He cannot, because He will not, capriciously override justice.
Justice is the reason Jesus had to die. God, in accord with justice, tried and convicted all of us because of our sin. No person convicted in the courts of heaven can then be set free without the demands of justice being met. Justice and judgment must be answered. Jesus chose to answer the demands of justice on behalf of all who believe and trust His Gospel. God's Love and Justice required that Jesus take our judgment upon Himself, thus fulfilling our obligation to the just demands of the law of God, and opening the door for eternal reconciliation.