One last observation on Gisela Stiker's article, "Origins of the Concept of Natural Law" . . .
Consider the following paragraph from that article:
As regards the question of natural justice, Aristotle insists, against the relativist, that it is not true that what the law prescribes varies completely arbitrarily from one society to another. There is a common core of laws, often unwritten, that can be seen to be part of any legal system--those laws that forbid murder, and fraud, for example--and these laws prescribe what is naturally just in the sense of being a necessary part of the order of any human community (EN V 7, 1134b17-30). But this view, that some laws are natural in that they prescribe what is naturally just (Rhet. I, 1373b 1-18), should not be confused with the theory that there is a natural system of law that defines right conduct.Add to the view that Striker here ascribes to Aristotle only that:
(i) laws that belong to this 'common core' are naturally recognized by us--that is, they are typically identified by us, and acknowledged to have force, apart from training or instruction; and thatand one then has a very good statement, I think, of the theory of natural law. These further points are presumably the important ones, if we are inquiring whether Aristotle had a 'concept of natural law'. (In my view it is likely that he endorsed (i) but unclear whether he would have endorsed (ii).)
(ii) these naturally just laws have priority over other laws, in the sense that other laws have no authority if they contravene a law that belongs to this 'common core';
Striker denies that the 'concept of natural law' is found in Aristotle only because she (strangely) thinks it is part of that concept that natural laws actually define what justice is, and that natural laws must somehow have the same extension as human positive law (it cannot be, she apparently thinks, that only some human laws express or articulate the natural law).
Needless to say, her essay then becomes an exercise in which the desired result is built in from the start: she defines the 'concept of natural law' in such a way that only the Stoics (if even they) could have originated it.