Definition of 'Natural Law'
A set of rules inherent in human behavior and human reasoning that governs human conduct. Natural law is preexisting and is not created in courts by judges. Philosophers and theologians throughout history have differed in their interpretations of natural law, but in theory, natural law should be the same throughout time and across the world because it is based on human nature, not on culture or customs.
An example of natural law, as interpreted by Thomas Hobbes, is that judges should be impartial. Other major philosophers of natural law include Aristotle, Thomas Aquinas and Lysander Spooner.
Investopedia explains 'Natural Law'
The opposite of natural law is "positive law" or "man-made law." Positive law may be based on natural law, but not the other way around. Positive or man-made laws include laws such as the speed at which individuals may drive on the highway and the age at which individuals may legally purchase and consume alcohol. While natural law typically applies to philosophy, it is also extensively used in theoretical economics.