Political theories based on right can very easily dissolve justice into right. Such a dissolution involves saying that there is nothing to justice beyond preserving, delineating, and defending rights. Let’s stipulate that all accounts of justice are in fact rights- relative, that is, that every act of justice is inseparable from the reality that such and such is owed to someone by right. What problem is there in simply using “right” as a proxy for “justice”? Won’t we get exactly the same results?A full rights theory can only be developed within ethics, or a political theory that is built upon "ethics" and the good. The problem is not with rights language, but with the ethical foundation that supports it.
Justice is the virtue of right operation to others. As a virtue, it is confers good on the one who has it, as giving right operation to others it confers some good on others. Notice that from one and the same action, good necessarily flows into a multitude: the one who acts and another. Right is not like this. Right captures the aspect of justice that speaks of “right operation to others”, but it prescinds from how such an operation needs to be perfective of the one from whom the operation flows. Right is a kind of abstraction in the mind that cannot be an abstraction in reality: the separation of “giving what is due” from the moral perfection of the giver. There is nothing wrong with these abstractions, and political thought needs to make them, but there is a blind side to the abstraction that we need to be aware of.
A full rights theory needs to recognize how the actuality of right- the satisfaction of right- is a good that is not limited to the one with the right, but it belongs both to the one who receives the good by right and the one who provides it to him. There is a single good which flows into two persons in different modes; but it flows in a higher mode into the one who acts or gives since it flows into him as virtue. A full rights theory would be a way of leading to a recognition of the superabundance of justice (where “superabundance” means “a good not limited to one nor diminished by being common”)
Notice that it is not enough to include a notion of “duty” as a correlative of right, though this is necessary. Neither right nor duty speaks to a superabundant good, flowing in diverse modes. Rights based theories must be perfected in one way by relating them to duties and in another way by relating them to justice.