My gut feeling says there is a Natural Law, and , looking around on the net, i'm obvious not the only one... On this page I want to explore what I can find and /or think and play the linking game again. First a selection of definitions. Start with a 'authority' on all things law; Blacks Legal Dictionary.
"Jus Naturale, the natural law, or law of nature; law, or legal principles, supposed to be discoverable, by the light of nature or abstract resounding, or to be taught by nature to all nations and men alike, or law supposed to govern men and peoples in a state of nature, i.e. in advanced of organized governments or enacted laws"
(Black's Law Dictionary, 3rd ed., p. 1044)
The medieval/legal definition:
Natural law cannot be defined in the way that positive law is defined, and to attempt to do so plays into the hands of the enemies of freedom. Natural law is best defined by pointing at particular examples, as a biologist defines a species by pointing at a particular animal, a type specimen preserved in formalin. (This definition is the most widely used, and is probably the most useful definition for lawyers)
The historical state of nature definition:
Natural law is that law which corresponds to a spontaneous order in the absence of a state and which is enforced, (in the absence of better methods), by individual unorganized violence, in particular the law that historically existed (in so far as any law existed) during the dark ages among the mingled barbarians that overran the Roman Empire.
The medieval / philosophical definition:
Natural law is that law, which it is proper to uphold by unorganized individual violence, whether a state is present or absent, and for which, in the absence of orderly society, it is proper to punish violators by unorganized individual violence. Locke gives the example of Cain, in the absence of orderly society, and the example of a mugger, where the state exists, but is not present at the crime. Note Locke's important distinction between the state and society. For example trial by jury originated in places and times where there was no state power, or where the state was violently hostile to due process and the rule of law but was too weak and distant to entirely suppress it.
The scientific/ sociobiological/ game theoretic/ evolutionary definition:
Natural law is, or follows from, an ESS (evolutionary stable strategy) for the use of force: Conduct which violates natural law is conduct such that, if a man were to use individual unorganized violence to prevent such conduct, or, in the absence of orderly society, use individual unorganized violence to punish such conduct, then such violence would not indicate that the person using such violence, (violence in accord with natural law) is a danger to a reasonable man. This definition is equivalent to the definition that comes from the game theory of iterated three or more player non zero sum games, applied to evolutionary theory. The idea of law, of actions being lawful or unlawful, has the emotional significance that it does have, because this ESS for the use of force is part of our nature.