Ethics and Authority in International Law attempts to examine the development and structure of international law from the standard jurisprudential dichotomy of naturalism versus positivism. Although many contemporary textbooks of international law provide an outline of this debate there is yet to be any full scale study. Rubin’s work, to some extent, fills this gap.

After reviewing the meaning of the terms naturalism and positivism, the author explains how these positions have informed the reasoning, or rather provided the justification, for developments in international law. He illustrates this by examining the formation of the international law prohibiting piracy and the slave trade and concludes that, while sometimes extolling naturalist rhetoric, 19th century international lawyers were thorough-going positivists.

Rubin provides an expert overview of the international legal theories of Pufendorf, Woolf and Suarez (in fact this may be the best overview available), before outlining his own views. For Rubin, positivism and naturalism are nebulous terms which contain a whole host of sub-concepts: Positivism is associated with the familiar notions of “dualism”, “State sovereignty”, “conflicts of laws” and “conflicts of jurisdiction”. “Naturalism”, conversely, addresses such ideas as “monism”, “universal crimes” and “universal jurisdiction”.

Rubin then uses these themes as the background to insightful analysis of the 17th and 18th century reasoning adopted to ground the illegality of the slave trade and piracy. For the naturalist these two crimes must be considered “universal crimes”, which can be enforced by any State. For the positivist, they must be considered as a question concerning the jurisdiction a State may have to capture and punish pirates and slave traders. Rubin shows that the reasoning in this period is firmly fixed within the positivist tradition (jus inter gentes), while displaying superficial traits of naturalism. He must be congratulated for identifying the operation of vacuous moral ideologies which muffle hard-nosed positivist negotiations leading to treaty formation.