Yes, that is the classical view. In fact, this view is what drove the philosophers to search for a natural law or a law of reason.
In ancient Greek, ethos and nomos are (near-)synonyms. Nomos means, in developmental order, “way, habit, custom; convention, principle; law”. In its sense of “convention, principle”, it was a if not the standing antonym of physis, “nature”. So a “natural law” is a paradoxical concept in the classical view. One should compare “positive law” or “positive right” on the one hand, and “natural law” or “natural right” on the other. Natural is what is not posited (by persons).
A similar discrepancy can be found between law and reason (logos). Consider astronomy and astrology. In Presocratic times, astrologia still meant “astronomy” (for example in Heraclitus). However:
“In Latin and later Greek, astronomia tended to be more scientific than astrologia.” (http://etymonline.com/index.php?term=astronomy)
And that’s certainly the way it is (considered) now, of course. Astronomy supposedly describes the physical laws of celestial objects–which are not conventions, let alone mere habits–, whereas astrology reads reason (sense, meaning) into the ways of celestial objects.
But all this has been uprooted by radical historicism. The God of the philosophers, Reason, is dead; nature is history. Formerly, nature or the Reason in nature was grasped by something likewise considered natural (eternal): human reason, the Reason in man. Now human reason is understood to be historical, a product of evolution; and not a finished product, never finished, but always subject to evolution. Nature itself, existence, the cosmos, or whatever you wish to call it is now understood to be wholly in flux–or is that only a misunderstanding rooted in the current form of human reason?..