I attended the Federalist Society Academic Conference last week. Due to juggling schedules, I was late to a session in which natural law was discussed. Because I was late to the discussion, I can't give a very reliable summary of the main talk, although I intend to listen to it when the MP3 becomes available. It did provide an interesting study in purely secular natural law thought though.
The presentation that got my attention was one that addressed a change in US military law under which a soldier's right to self-defense was altered in the mid-2000's such that what was once a personal decision had been transferred up to the unit commander. The impact was that where once a soldier had a degree of autonomy in deciding whether to protect his life or a fellow-soldier's life, this was now removed from him. The proposition in the lecture was that this violated natural law.
In typical Federalist Society patterns, a panelist was chosen to counter the proposition being advanced, In this case, the speaker was Roderick Hills, Jr. of NYU. He was presented as, and initially described himself as a positivist. Ultimately, he refined his philosophy as being that of a welfare consequentialist. As an aside, welfare consequentialists talk about values a great deal. I think that apart from eschewing objective moral values, consequentialists have an analytical approach that sounds a lot like natural law advocates.
Hills advanced an argument that individuals who join the army surrender any claimed right of self-defense. I think he had the better end of the argument by far. I am not much of an advocate of rights talk in any case, but it seemed to me that advancing a policy of military tactics based on natural law seemed almost silly at some point. It gave me the same kind of apprehension I get when individuals apply just war thinking to a military venture by treating the just war arguments as a list of values under which the majority of values wins.
I don't think natural law works this way. Apart from vague but important universal principles that impact the highest level of military theory (one ought not to recklessly subject troops to danger to accomplish a minor goal, one ought not to go to war merely to seek natural resources), we can't manage tactics effectively by asking "what does natural law teach us here?"