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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. The research group is led by Christian Marxsen.


Challenges to the law & contestation

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, that is from the perspective of states’ challenges to the law. The aim is twofold: by better understanding contestational legal evolution the research will, concomitantly, refine our understanding of how international law’s stability over time and bindingness at a given point coexist with negations of the law and the spread armed conflicts. We need a concept of illegality in order to fully comprehend the functioning of the law and its stability as well as fragility.

The limits of binarity

Core to legal rationality is to offer a binding binary code that distinguishes between legality and illegality – normatively requiring subjects to follow and act in accordance with the law. However, as international law is a decentralized and multipolar order such binarity does not always fulfil the expectations towards international law. Contestation of rules and negations of the law are intrinsically tied to the process of legal change and normative development and can therefore not simply be ruled out as ‘the other’ of international law. The project asserts that the binarity at least partly disintegrates and that shades of illegality are inherent to the international legal process. International law thus depends on processes in which its own rules are contested. Moreover, in many cases even firmly established (‘hard’) international rules do not always (as suggested by traditional notions) function in binary terms, as they are too ambiguous and controversial to clearly guide states’ conduct.

Unpacking Illegality

The project analyses different forms and facets of illegality that have distinct effects on the law. For example, states a) may dispute the application of a rule to a specific conflict; b) may deliberately violate the law in order to foster its development; c) may negate the law and act as ‘outlaws’; d) may pose systemic challenges (e.g. ‘socialist international law’; e) or they may behave and speak ambiguously, thereby creating spheres of indeterminacy within the law and opening up the law to political processes. The project researches the nuanced modes that international legal doctrine and practice have established in order to integrate these forms of illegality into the functioning of the overall system. It shows that in theory as well as in practice, not all violations of the law have the same meaning in normative terms. They require different explanations and, in fact, receive different treatment in the practice of states.


It terms of method the project rests on a tripartite structure:

- classical legal (doctrinal) analysis with a particular focus on the sources of international law, including the research of case studies;

- empirical research employing social science methods aiming to illuminate states’ approaches and attitudes towards contestation and illegality;

- conceptual work aiming to establish a theoretical account of the principles of the evolution of the law, capable to grasp international law’s adversarial elements.

Research Group Members

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

Dr. Carolyn Moser - Senior Research Fellow

Alexander Wentker, MJur (Oxford) - Research Fellow


Student research assistants:

Felix Herbert

Paula Jenner

Florian Kriener


Christian Marxsen

Violation and confirmation of the law - The intricate effects of the Invocation of the law in armed conflict, Journal on the Use of Force and International Law 5/1 (2018),

Cleavages in international law and the danger of a pull towards non-compliance, 22. January 2018,, doi: 10.17176/20180131-120116.

International law in crisis – Russia’s struggle for recognition, German Yearbook of International Law 58 (2015), 11-48 (2016), online available as: MPIL-Research Paper No. 2016-05, 2016.

Carolyn Moser

Bring claims if you can—On the intricate arrangements for claims arising from extraterritorial EU security and defence activities, ZaöRV 3 (2018), forthcoming, online available as contribution in: MPIL Research Paper No. 2018-19.

Legal uncertainty and indeterminacy—immutable characteristics of the OSCE? (with Anne Peters), in Mateja Steinbrück Platise, Carolyn Moser, Anne Peters (eds.), The Legal Framework of the OSCE, Cambridge University Press, 2019, pre-print version available as: MPIL Research Paper No. 2018-16.

Awakening dormant law—or the invocation of the European mutual assistance clause after the Paris attacks, Verfassungsblog, 18.11.2015.