The Question and Answer section for Paradise Lost is a great resource to ask questions, find answers, and discuss the novel.
This is a pretty open ended question for this short space. God is able to balance divine justice with mercy, grace, and salvation. Your question depends on what type of justice you are referring to.
He has to much pride to ask god for forgiveness..because he thinks that he is better than god
Milton will be writing an epic poem in which a disgraced Satan, and his devils, challenges God's omnipotence.