Aristotle on Justice

(From The Nicomachaen Ethics, Book 5, Chapter 7)

Aristotle never developed the notion of "social justice" as a distinct category of justice, but he did distinguish between two kinds of "political justice," which he called "natural" and "legal" justice. Since Cronin has used the terms "legal justice" and "social justice" interchangeably, it is tempting to think that the following passage from Aristotle's Nicomachaen Ethics is about what we today call Social Justice. But is it? It is also tempting to read Aristotle's distinction between legal and natural justice as an attempt to apply an early form of social construction theory to the former domain (that of legal justice). But what are we to think of his last sentence (the bold face is ours), in which Aristotle seems to suggest that some social constructions are more natural (and presumably better) than others?
Of political justice part is natural, part legal — natural, that which everywhere has the same force and does not exist by people's thinking this or that; legal, that which is originally indifferent, but when it has been laid down is not indifferent, e.g., that a prisoner's ransom shall be a mina, or that a goat and not two sheep shall be sacrificed, and gain all the laws that are passed for particular cases, e.g. that sacrifice shall be made in honour of Brasidas, and the provisions of decrees. Now some think that all justice is of this sort, because that which is by nature is unchangeable and has everywhere the same force (as fire burns both here and in Persia), while they see change in the things recognized as just. This, however, is not true in this unqualified way, but is true in a sense; or rather, with the gods it is perhaps not true at all, while with us there is something that is just even by nature, yet all of it is changeable; but still some is by nature, some not by nature.

It is evident which sort of thing, among things capable of being otherwise, is by nature; and which is not but rather is legal and conventional, assuming that both are equally changeable. And in all other things the same distinction will apply; by nature the right hand is stronger, yet it is possible that all men should come to be ambidextrous. The things which are just by virtue of convention and expediency are like measures; for wine and corn measures are not everywhere equal but larger in wholesale and smaller in retail markets. Similarly, the things which are just not by nature but by human enactment are not everywhere the same, since constitutions also are not the same, though there is but one which is everywhere by nature the best.