Justice is the virtue that governs our relations to others. In our own time, we are more familiar with understanding our relations to others in terms of rights, and (begrudgingly) duties. There is a certain equivalence between justice on the one hand and rights/ duties on the other, for inasmuch as justice is a relation of what is owed between, say, myself and another, I can view “rights” as what is owed to me, and “duties” as what I owe to others.
But we can never replace justice with rights/ duties, for there is an essential difference between them: having justice makes a man good, but having rights or duties do not. When we try to speak of rights or duties apart from the virtue justice we will ultimately not be able to account for why either rights or duties are good.