Many elements of current positive public international law (PIL) originated in various theories of natural law, ranging from conceptions of sovereignty to the law of the sea and the refugee conventions. PIL has developed extensively, indeed so much that its fragmentation is a problem. Some therefore argue that since PIL has come of age, it is time to kick the ladder of natural law away. PIL and state consent-centered International Legal Positivism have replaced and improved the contributions of traditional natural law, leaving those old theories dead.
The main task of this article is first, in section 1, to sketch the contours of a 'rational reconstruction’ of natural law theories, INLT. It identifies some features shared by many traditional and some current self-described theories of natural law relevant for this issue - not to defend them but to present them in their best light. Section 2 identifies some questions that INLT address. The central issue is the legitimate authority of PIL and the sovereign states and ICs it helps constitute: whence and whither their claim to rightful authority? Further issues concern the sources of PIL and their interpretation by judges of ICs. Section 3 considers whether these forms of INLT stand up to criticisms from Waldron, Koskenniemi and others. Section 4 returns to consider how INLT may contribute to some of PIL’s current challenges and alleged crises, including concerns about ineffectiveness, principled non-compliance, renationalization, indeterminacy and its role in domination.
