In law, natural law is the doctrine that just laws are immanent in nature (that can be claimed as discovered but not created by such things as a bill of rights) and/or that they can emerge by natural process of resolving conflicts (as embodied by common law). These two aspects are actually very different, and can sometimes oppose or complement each other, although they share the common trait that they rely on immanence as opposed to design in finding just laws. In either case, law seeks more to discover a truth that is considered to exist independent and outside of the legal process itself, rather than simply to declare or apply a principle whose origin is inside the legal system.
The concept of natural law was very important in the development of Anglo-American common law. In the struggles between Parliament and the monarchy, Parliament often made reference to the Fundamental Laws of England which embodied natural law since time immemorial and set limits on the power of the monarchy. The concept of natural law was expressed in the English Bill of Rights and the United States Declaration of Independence -- and by 19th-century anarchist and legal theorist, Lysander Spooner.
Compare with: Natural justice
See also: human rights
There is a also political Natural Law Party.