If i raise a human in complete enclosure, so that has never contact with other humans, he will only live by the rules in himself that he has by nature.
so when he sees a human, he will think it's just an other animal and he will try to kill it to eat it.
he will certainly not think: hey, i may not kill that one.
i'll give another little exemple:
if you could go back in time and kill sadam hoesein, would you do that? (not including the time paradox)
you would still kill a person then, and that violates directly one of the 10 commandements.
or if you see a person on the ground, who is suffering terribly, and can not be helped anymore, and will die in some hours.
his suffering is enormous, gigantic, he is about to lose his mind.
would you kill him to end the horrific suffering?
because if you don't, you only let him die more slowly but with an incredible pain.
because of this, i don't think there is an universal moral law.