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Shades of Illegality in International Peace and Security Law (SHADES)


The SHADES-project is established as a Max Planck Research Group with a funding period from 2018-2022. Its funding was extended for a period of two years until December 2024. The research group is led by Christian Marxsen.


Under the title ‘Shades of Illegality in International Peace and Security Law’ the research group analyses international peace and security law from the perspective of deviant behaviour and from the perspective of states’ challenges to the law. The research is premised on the assumption that contestation of norms fulfils an important function in the multipolar order of international law. Such contestation and deviance is not only important for shaping and substantiating existing legal principles, it also allows a normative system without a central legislator to develop. On the other hand, illegal actions constitute a permanent danger to the international legal order as continuous violations of the law may lead to a decline of the law’s normative power.

The research project aims to unpack the different dimension, types, and effects of illegal actions. How is illegality ‘constructed’ in the first place? Where does the law allow to distinguish between legality and illegality in a binary mode and  where, does it, on the other hand, only offer a language for the articulation of political interests? When are illegal actions even a legitimate tool for shaping and amending existing legal rules and what are the concrete dangers that different types of illegality pose?

The interdisciplinary research project addresses these question from multiple angles, conducting classical legal (doctrinal) analysis with a particular focus on the sources of international law, including the research of case studies, but it employs also methods of social science aiming to illuminate states’ approaches and attitudes towards contestation and illegality.

Research Group Members

Prof. Dr. Christian Marxsen, LL.M. (NYU) - Research Group Leader

Leonie Brassat - Research Fellow

Felix Herbert - Research Fellow

Malcolm Jorgensen - Senior Research Fellow

Florian Kriener - Senior Research Fellow

Alexander Wentker- Senior Reserach Fellow


Student Research Assistant:

Lukas Hemmje


Relevant Publications

Christian Marxsen, Völkerrechtsordnung und Völkerrechtsbruch: Theorie und Praxis der Illegalität im ius contra bellum, Mohr Siebeck, Ius Publicum, 2021, DOI: 10.1628/978-3-16-160759-2, 577 pages.

Max Lesch/Christian Marxsen, Norm Contestation in the Law Against War: Towards an Interdisciplinary Analytical Framework, Zeitschrift für ausländisches öffentliches Recht und Völkerrecht 83 (2023), 11-38.