My latest publication for 2025 is out. Together with Antonia Waltermann, we co-edited a Special Issue of the Hague Yearbook of International Law on The Logic(s) of International Law.
The motivating question for this Special Issue is simple, but the answers are not: what role does logic play in international law? And is there a single logic at work, or several?
Classic debates in legal theory already show why this matters. From the normative systems of Alchourrón and Bulygin, to Susan Haack’s critique of over-formalising law, the field has long wrestled with how far logical analysis can take us. Analogies such as Hofstadter’s MIU game make the point clearly: formal systems can be internally coherent and yet blind to meaning, context, and practice. International law, with its decentralised structure, normative pluralism and highly political character, emphasises many of these problems. The question, then, is not whether logic matters, but which logics are appropriate, and how they can help legal reasoning without mistaking formal validity for legal soundness and justice.
The Special Issue brings legal theorists and international lawyers into direct conversation. Several contributions stand out:
Torben Spaak examines consistency in international law and asks what it means for a normative system to guide behaviour rationally. Antonia Waltermann develops an account of systematicity and norm conflicts that emphasises the constructivist role of legal reasoning. David Lefkowitz reminds us of the limits of logic, arguing that the life of international law lies in professional practice and experience, not deduction alone. Ulf Linderfalk revisits rational reconstruction as a method for clarifying international legal reasoning. Jaap Hage offers a provocative account of the logic of human rights, treating rights as intermediary nodes within a network of legal statuses. My own contribution explores how logical tools can clarify the interaction between international humanitarian law and human rights law.
My central takeaway is not that logic replaces law, but that multiple logics operate within international law, each suited to different questions, practices, and theoretical commitments. Understanding the role of logic sharpens legal argumentation without denying the political, historical, and human dimensions of international law.
For those interested in legal reasoning, norm conflicts, fragmentation, or the foundations of international law, this Special Issue offers an interesting set of perspectives.
Read the full chapter: The Logic(s) of International Law – Hague Yearbook of International Law (Brill | Nijhoff)
Henrique Marcos 