Within the classical tradition of the natural law, the scholastic theologians of the sixteenth and seventeenth centuries describe this law as simply necessary, as well as immutable and universal. They conceive it, moreover, as an objective order independent of God’s will. However, not all scholastic theologians understand the immutability of natural law in the same way, nor does the term “natural law” refer to exactly the same thing: whereas for some it is the “law of nature”, for others it is the “law of natural reason”. So, the article addresses the main differences in the theories of these scholastics on natural law.