Is knowledge of right and wrong written on the human heart? Do people know God from the world around them? Does natural knowledge contribute to Christian doctrine?
Stephen J. Grabill, Ph.D., Research Scholar in Theology and Executive Editor, Journal of Markets & Morality, and author of Rediscovering the Natural Law in Reformed Theological Ethics, has written an article touching on these questions (which questions are more fully addressed in his book) entitled Natural Law and the Protestant Moral Tradition about four ways in which natural law is important to the doctrines of the church. These are:
(1) none of the confessional documents of the magisterial Reformation rejected the doctrine of natural law;
(2) natural law played a significant role in the three uses of law articulated by the Reformers;
(3) the Reformers did not play special revelation off against general revelation, as tends to happen today, both were considered legitimate forms of revelation that served distinct roles in theology; and
(4) the Reformers felt no tension in affirming a strong doctrine of original sin, on the one hand, and natural law, on the other.
The article is short, and he provides some background for these points in the paper. If you have the time, there is also an audio/MP3 of a lecture he gave based on this paper in which he begins by reading the paper with a few comments, and then continues with a great deal of additional information (which is undoubtedly contained in his book) in a lecture that can be found here.