This is complete nonsense.
You have already accepted some sort of universal moral standard by which ALL human beings ought to abide by -- although you pretend to be dumb about it.
You have the universal declaration of human rights (and all the conventions consequent to it). You have an idea of universal justice by which international law is based. You have the idea of the rule of law based on the consent of the governed to be governed. Do you need me to dumb this down further?
Take note, the concept of natural law is the basis by which you, yourself, criticize positive law. That is how just about anyone can appear on the international news saying the prc, north korea, iran, saudi arabia, etc. are human rights violators. And on this basis are diplomatic and economic pressures brought to bear on them.
What in hell are you thinking about, eh?
Why do you persist on dumbing down this discussion, hmmm? Is that the only thing you are capable of understanding? Okay, let's dumb this down to your level and see if it holds any water.
First of all, abraham was the leader of a NOMADIC tribe. A nomadic tribe, by nature, DOES NOT owe any allegiance to any body politic -- either by consent or force -- except their own. A harsh environment in which one lives in dictates a harsh socio-political setting. Its a matter of SURVIVAL that abraham, being the leader of his tribe, is a law unto himself.
And if, by some unimaginable quirk, a jury of one's peers is the requirement of justice at that time, one cannot find any objective jury for hundreds of miles around.
And if an objective jury was indeed formed, there is no legal precedent that would allow abraham to subject himself to the power of this jury -- except by force.
And if abraham did subject himself to the power of this jury, they would readily acquit abraham simply because he possesses unquestionable SOVEREIGNTY over his subjects. Merely refusing any member of his tribe the protection of the tribe (which is abraham's prerogative, by RIGHT) would have the same effect as killing this person with his own hands.
And even if you are permitted to question abraham's sovereign right (bear in mind that you cannot, presently) you can only do so according to a power higher than any earthly power -- meaning god's natural law -- the same power who ordered the ritual in the first place.
So, you can present this argument in a court of morons and still, you would loose.