The Natural Law is what all men know to be right and wrong. My first exposure to this concept was in the CS Lewis book, The Abolition of Man. I was delighted to have found this excellent book on the web and encourage all to read it. At the very least, please pause to briefly take a look at the Appendix where Lewis speaks of the codification of the Natural Law, which he calls Tao, in many of the religious writings from around the world. The acknowledged source of the Natural Law is of course God. When man teaches that the Natural Law is wrong - and substitues other things as right, he is on the slope to the abolition of man. (e.g. Episocpal Church USA and homosexuality).
On the Acton web site there is an excellent interview by Religion and Liberty Journal with Dr. J. Budziszewski entitled The Natural Law Is What We Naturally Know that looks at his new book, What We Can't Not Know-A Guide. His testimony at the end of the interview about his movement from atheism to Christianity is very interesting. Budziszewski, like Lewis, is an Anglican, and his emphasis on Reason is in the Anglican tradition. He also makes the point that there is no conflict between Scripture and the Natural Law.
An awareness of the Natural Law is important for Centurions seeking to Fear God and do what is right. The Scriptures speak of following the Spirit of the Law that gives life and not the letter of the law that kills [2Cor 3:6] and the Natural Law does indeed exist for all [Rom 2:14-15] Certainly, God is the author of the Natural Law. The Law that God has written on our hearts must guide us in our day-to-day encounters as we endeavor to live in this world and do what is right.
If you are interested in exploring Natural Law further, and would like to read from works throughout the ages, you may find this Natural Law/Natural Right Page resourceful.