Antigone

Why not? It was not Zeus who gave the order.
And Justice living with the dead below
has never given men a law like this.
Nor did I think your pronouncements were
so powerful that mere man could override
the unwritten and unfailing laws of heaven.
These live, not for today and yesterday
but for all time.*
What is found in man's heart will inevitably come out in his literature, in his tales, in his "oral tradition". Now, we must give some important background for the above passage, just in case there exists someone reading this blog who has not yet had the pleasure of reading (or watching) "Antigone."
Antigone, daughter of Oedipus, goes to bury her brother, who has died in mortal combat. The new ruler, Creon, makes a law that forbids Antigone from burying her poor brother, because he was Creon's rival claimant to the throne. Antigone does her family duty and buries her brother anyway, knowing full well that Creon will exact the death penalty against her. So, what does she think of Creon's decree? Sophocles gives Antigone's answer in the profound passage quoted above.
So why this passage to open a blog on natural law? Because, in a way that touches the human heart, it conveys profound truths about the natural law: Natural law is based on eternal law (God's design for the universe, especially for the human person), it is unchangeable and universal (for human persons of every place and every time), and it cannot be overridden by any positive law, whether civil or ecclesiastical.
With laws that fail to protect completely the human life in the womb and proposed laws that would obliterate all legal protection against abortion (F.O.C.A.) and the legalization of "gay marriage" in some states, the primacy of the natural law over human positive law would seem to be a very pertinent topic for our day and age. But that's the topic for a future posting by this author--or perhaps one of you bloggers out there would like to "write in" about that.
*(Sophocles, Oedipus the King and Antigone, Peter Arnot, trans., New York: Appleton-Century-Crofts, 1960, p.76)