In his ‘Perpetual Peace’, Kant indicts the natural law tradition (Grotius, Pufendorf, Vattel) as ‘miserable comforters’ whose principles and doctrines ‘cannot have the slightest legal force’. The indictment emerges from Kant’s critique of natural law in both its empirical and rationalist variants as unable to uphold a really ‘binding’ notion of cosmopolitan legality. Since the early 1990s a new literature has emerged in the International Relations field that speaks about the effectiveness and legitimacy of international law as a form of supranational ‘governance’. This article argues that that literature raises precisely the same problems that Kant detected in early modern natural law. Like the latter, this literature is best seen as an attempt to appropriate the voice of international legality to a fully instrumentalist discipline dedicated to serving the interests of power. KEY W ORDS ♦ governance ♦ international law ♦ International Relations theory ♦ Kant ♦ natural law