This article explores the normative international relations theory of Mervyn Frost. Frost's unorthodox approach to questions of human rights offers a way through the political and philosophical morass that has often threatened to obscure the most pressing issues of our time. Significantly, Frost claims to able to ‘construct’ a background justification for international ethics that can unite the demands for sovereign autonomy with declarations of human rights. In doing so Frost attempts to offer an new understanding of universal ethics and thus of the role of human rights in international politics. Acknowledging the importance of this approach, this article examines two issues that arise from Frost's ‘constitutive theory’ and seeks to offer a signpost for the future development of human rights theory.