Hello josephback,
I was just doing a little reading on your question. Now, as I understand it and as Paul clearly writes the natural laws are written in our hearts and are universal previous to Christ and after Christ (Romans 2.15 onward). However, we have the New Law of he Gospel which was given to us by Christ Jesus and this is the Grace we receive from the Holy Spirit.
Now, from what I understand the New Law is not universal but is given to those who believe in Jesus and are baptized in the name of The Father, The Son and The Holy Spirit. Saint Thomas quotes Augustine who wrote that this law is written in our hearts: “as the law of deeds was written on tables of stone, so is the law of faith inscribed on the hearts of the faithful”: and elsewhere, in the same book (xxi): “What else are the Divine laws written by God Himself on our hearts, but the very presence of His Holy Spirit?” I personally, would express it that the New Law
dwells in our hearts, but, it can be said that it is written. Notice Augustine refers to the New Law as Divine Law (versus Natural Law).
From the Summa:
I answer that, “Each thing appears to be that which preponderates in it,” as the Philosopher states (Ethic. ix, 8). Now that which is preponderant in the law of the New Testament, and whereon all its efficacy is based, is the grace of the Holy Ghost, which is given through faith in Christ. Consequently the New Law is chiefly the grace itself of the Holy Ghost, which is given to those who believe in Christ. This is manifestly stated by the Apostle who says (Romans 3:27): “Where is . . . thy boasting? It is excluded. By what law? Of works? No, but by the law of faith”: for he calls the grace itself of faith “a law.” And still more clearly it is written (Romans 8:2): “The law of the spirit of life, in Christ Jesus, hath delivered me from the law of sin and of death.” Hence Augustine says (De Spir. et Lit. xxiv) that “as the law of deeds was written on tables of stone, so is the law of faith inscribed on the hearts of the faithful”: and elsewhere, in the same book (xxi): “What else are the Divine laws written by God Himself on our hearts, but the very presence of His Holy Spirit?”
Nevertheless the New Law contains certain things that dispose us to receive the grace of the Holy Ghost, and pertaining to the use of that grace: such things are of secondary importance, so to speak, in the New Law; and the faithful need to be instructed concerning them, both by word and writing, both as to what they should believe and as to what they should do. Consequently we must say that the New Law is in the first place a law that is inscribed on our hearts, but that secondarily it is a written law.
To be clear, even though the New Law can be said to be written in our hearts, this law is not what Jeremiah and Paul were referring to but instead they were referring to Natural Law.
Hope this helps.
Anyone and everyone is welcomed to correct me if I am mistaken.
Peace,
Abba
P.s. Of course, ultimately, Natural Law is divine because it was instituted by God.