Jeremy Waldron (New York University – School of Law) has posted Ius Gentium: A Defense of Gentili’s Equation of the Law of Nations and the Law of Nature on SSRN. Here is the abstract:
The relation between the law of nature and the law of nations (ius gnetium) remains unclear. This paper examines Gentili’s apparent equation of the two, and it considers more generally how abstract natural law reasoning might be improved by the sort of empirical/comparative law reasoning (as we would call it) that thinkers like Gentili, Grotius and others engaged in when they tried to determine what natural law teaches us about the regulation of war.
And from the paper:
[A]s one reads Gentili’s equation of natural law and the law of nations, it seems to bring the two concepts together on the other side—the empirical side—of the rational/empirical divide. We find out what the law of nations is by diligently investigating the laws and customs that are in use among all nations of men; we ask traders, for example, for stories about foreign lands.6 What Gentili equates with the law of nature are the laws and customs that have seemed acceptable to all nations (or, as it turns out, most nations—for “as the rule of a state and the making of its laws are in the hands of majority of its citizens, just so is the rule of the world in the hands of the aggregation of the greater part of the world”)7—which have established themselves in the world, not necessarily by any explicit agreement but by “successively,” nation by nation, seeming acceptable to most men. That is plainly an empirical matter. And if the law of nations in this sense is being equated with the law of nature, then we have moved the whole jurisprudential enterprise over from the side of pure moral reason to the side of positive legal inquiry.
And:
[O]n the analysis I have given and on the position taken by Gentili, this sharp dichotomy between pure natural law reasoning—which looks like moral philosophy—and the citation of positive law authority (e.g. from other countries) is simply misconceived. Natural law is better understood as something discernible most reliably from a careful, critical and morally well-informed study of universal or consensual human practices. And the citation of foreign law might be understood as an appeal to the law of nations, the ius gentium, conceived now as a emergent body of law—of positive law—in the world, albeit a body of positive law whose apprehension requires moral discernment. Each of those positions seems worth taking very seriously, and if one takes them seriously, then I think that we can begin to see the virtue of Gentili’s assimilation of the one to the other in his equation of the ius gentium with the ius naturae.
Highly recommended.