The Logic(s) of International Law

This Special Issue of the Hague Yearbook of International Law is the outcome of the ‘Logic of International Law’ conference convened on 14th and 15th November 2022 at Maastricht University, Faculty of Law. The idea of the conference was to bring together scholars from public international law and legal theory to interact and discuss the logic(s) of international law. The combination of logic and public international law is perhaps not one that is immediately obvious or common, but we posit that there is fruitful ground at the intersection between the two fields. First and foremost, the understanding of logic adopted for this project is a broad one: logic is the field of study concerned with rules of good reasoning. Reframed in such a way, the combination becomes more obvious: reasoning is one of the core tools for lawyers in any field and public international law is no exception.
Still, organising a conference on the logic of international law was both a unique and challenging opportunity. This is for two reasons: on the one hand, existing legal logic is largely not built for public international law; on the other hand, lawyers may distrust the ‘cold mathematical approach’ of logic.
First, much of the existing work in legal logic either adopts a generalist approach or bases its analysis on domestic law, which has a structure that differs significantly from that of international law. Unlike domestic law, which typically features a hierarchical structure, international law lacks a formal and centralised framework. International law evolves through the direct actions of its subjects: states, international organisations, non-governmental entities, transnational companies, and even individuals. The continuous expansion of international law, characterised by the increase in the number of special regimes, presents complicated challenges to international cooperation in the form of normative conflicts. In this way, the insights derived from legal logic in the context of domestic law may not always be readily transferable to international law. In some cases, a ‘translation’ is necessary. In other cases, the distinctive features of international law demand the development of specific logical tools to deal with its particular matters. The challenges offered by international law provide fertile ground for logicians to refine, broaden, and validate their theories. At the same time, certain perspectives from logic may provide legal scholars with valuable analytical and conceptual tools for understanding international law.
Second, any endeavour that attempts to connect law and logic is inherently controversial, especially when it comes to the potential consequences of combining (seemingly) hard mathematical reasoning with the nuances of legal interpretation. Lawyers may worry that relying too heavily on logic could mechanise legal practice, making impossible the delicate balancing acts that may be necessary for delivering fair outcomes. They are concerned that placing too much importance on logical frameworks could lead to an insensitive approach to legal interpretation, which may overlook complex human experiences, moral considerations, and cultural contexts. In the age of generative artificial intelligence, the idea of mechanising legal interpretation using logical ‘if-then’ automations does indeed raise significant theoretical and practical questions about law and the involvement of human agency in norm application. A blind automation of legal reasoning could pose a threat to the fundamental nature of law, reducing it to a mere exercise in algorithmic deduction. This, however, is not the sole method to connect law and logic, nor is this the only possible understanding or type of logic available to law. It is feasible to bridge the two without compromising the human aspect, while maintaining – and indeed conceptualising – the possibility and need for exceptions and balancing. If logic is the study of correct reasoning, in both formal and informal ways, what reasoning approaches are suitable for public international law, and what can public international law and legal logic learn from and contribute to one another?
These, among other topics, were discussed during the conference, with the most important findings presented in the articles that comprise this Special Issue. Within its pages, readers will find a collection of perspectives, each offering a unique lens through which to examine the interplay between logic and international law. Despite the diversity of topics (and the sometimes opposing viewpoints expressed in this Issue), the collective dialogue has allowed us, the Editors of this Special Issue, to distil certain conclusions. Note, however, that these conclusions do not encompass the full range of opinions held by the authors contributing to this Special Issue. Instead, they reflect our particular perspectives as Special Issue Editors based on our engagement with the ideas discussed throughout the conference and in the subsequent articles.
In the following sections, we will elaborate on our conclusions. While presenting these conclusions, we will also provide the reader with an overview of the publications that make up this Special Issue and how they relate to one another. We will begin by explaining that we have found that there is a logic to international law, but it is not a singular logic. Rather, it is plural; there are logics of international law (section 2). With that in mind, we will examine what role that logic can play in international law, as well as its limitations (section 3). Then, we will reflect on the need for continued collaboration between lawyers and logicians to help understand and address some questions of international law (section 4). In the final section, we conclude by synthesising our conclusions, exploring the interrelationships between the contributions that compose this Special Issue, and offering a ‘field guide’ for readers on how to best engage with these contributions, depending on their particular interests and backgrounds (section 5).