How would justice in your fictional setting (magical or otherwise) be carried out? Who has the power to enforce justice and how did they get that power? What happens when justice is corrupted? If characters feel they should take the law into their own hands what drove them to this, are they successful and what do they actually do?
Revenge should have its repercussions shown clearly I think and this is where Shakespeare wrote so wonderfully with regard to Romeo and Juliet. This is the theme of my post tonight on Chandler's Ford Today. The Bard was right to show the stupidity of a relentless thirst for revenge. And it should be brought home it is the innocent (Juliet) who suffer most.
So how do you go about this in your stories? I'm not just thinking of novels here. A short sharp story about the theme of revenge/justice will find a home if written well enough. The universal themes never date after all.