natural law and Divine Law to the Rambam.

I am beginning to wonder if there is any real difference between natural law and Divine Law to the Rambam. The reasons for the laws we know were implicitly understood by the Chazal (Sages) except for the Red Heifer. But only later the Rambam spelled out the reasons.

But there does not seem to be any definite account of what Avraham Avinu's natural law approach might have been in the Guide. (That is Abraham the Patriarch). It is almost as if the Rambam is saying in order to get to natural law you have to keep the Torah. He certainly does not think of the legal structures of Ancient Greece as fulfilling the requirement of natural Law.
He puts the nomoi (laws) of the Greeks into the same area of the ravings of the Sabians in the Guide.
In the Guide, the Rambam makes clear most of the laws of the Torah are to bring to things that he considered natural law.