Concerning the genesis of, the purpose for, Natural Law…
Natural Law, moral law, exists as it was implemented by our Creator in conjunction with the creation of the angels as Natural Law acts as an arbiter of free will. Freedom of choice, volition, divine communicable attributes provided humanity by Elohim on the 6th-Day of Creation, is essential for love, relationship, intimacy, with our Creator to manifest with purity and authenticity.
Natural Law is also essential as a bulwark against unrestrained narcissism that would ultimately culminate in societal implosion which would thwart our Creator’s eschatological plan concerning the restoration of holiness, righteousness, to His Kingdom; chaos introduced into Elohim’s Kingdom via a rebellious, covetous, cherub angel; that chaos being causation for the creation of Time, matter, our Universe, as a temporary repository for Satan’s coup d’état; that coup having been relegated and partially constrained by Time and physics as Elohim deals with sin and rebellion via Messiah Jesus (1 John 3:8b).
Finally, Natural Law will be used by our Creator, Jesus Christ, at the “Judgment of the Condemned” (Revelation 20:10-15) to adjudicate Satan and the fallen angels (Revelation 20:10) along with the sin, rebellion, of humanity who has rejected the sovereign grace, the imputed righteousness of Jesus by faith in Him as our Messiah for the forgiveness of sin (John 3; 2 Corinthians 5:21).