When Russia launched its full-scale invasion of Ukraine in February 2022, it acted in clear violation of the international prohibition on the use of force set out in Article 2(4) of the UN Charter. Yet the Kremlin did not present the invasion as lawless. Instead, it used an elaborate legal narrative to justify the invasion, invoking anticipatory and collective self-defence, humanitarian intervention, and the duty to prevent genocide. Few international lawyers found these arguments persuasive. But what matters is that they were made at all.
This strategic use of international law to justify controversial security practices lies at the heart of the current research of Dr Sophie Duroy, a Lecturer from Essex Law School. Her work explores how states invoke, stretch or at times abandon legal justifications in matters of security and how these practices, over time, reshape international law itself.
Rather than asking only whether states comply with international law, Dr Duroy’s research examines what happens when law is used as a language of legitimation. Democracies and autocracies routinely invoke international law to defend conduct that stretches, distorts or openly contradicts its constraints. These legal justifications are made in courtrooms, in United Nations debates, in government policy documents and on the world stage through public diplomacy. These arguments may be unconvincing or openly self-serving, but they nevertheless play a role in shaping perceptions of legality and legitimacy on the global stage.
As Dr Duroy explains, ‘My interest in this question developed alongside my work on The Regulation of Intelligence Activities under International Law (Edward Elgar, 2023). What interests me is not only in what states do in the name of security, but also in what they say about these policies, namely, how they justify them using legal arguments. Strategic legal justifications shape perceptions of legality and legitimacy and, over time, can contribute to the erosion of the very norms they rely on.’
Law, intelligence and informal legal change
A central strand of this research focuses on intelligence activities. In a recent chapter (preprint) for the Research Handbook on Intelligence and International Law, Dr Duroy analyses how states have increasingly engaged with international law to defend controversial intelligence operations. She shows that intelligence communities have become normative actors under international law, influencing how legal rules are interpreted, applied and, in some cases, informally transformed.
By advancing expansive interpretations of legal norms - or by refusing to justify exposed operations altogether - states can contribute to gradual but significant legal change. Practices once presented as exceptional may become normalised, while the binding force of the underlying legal rules is weakened. In this sense, legal justification actively reshapes international law.
Dr Duroy develops a similar argument in another book chapter for a volume on State-Sponsored Assassinations in International Politics, where she examines how states frame assassinations in legal terms, often invoking self-defence or the laws of war. These justifications, she argues, do more than defend individual operations.
Drawing on cases ranging from U.S. drone strikes to more recent killings presented as ‘justice’, the chapter demonstrates how liberal democracies have contributed to the normalisation of assassination as a tool of statecraft. In a piece for The Conversation, coauthored with Luca Trenta and Emil Archambault, she examines the concrete effects of this normalisation with regard to Israel’s assassination of Hassan Nasrallah.
When legal justification disappears
More recent work, co-authored with Luca Trenta, examines a different but equally consequential development: situations in which states do not meaningfully attempt to justify their actions under international law at all. Analysing the United States’ abduction of Nicolás Maduro on 3 January 2026, the authors argue in Verfassungsblog that the most striking feature of the operation was not only its illegality, but the absence of a sustained legal rationale. Instead, official narratives focused on effectiveness, domestic authority and the moral unworthiness of the target.
This retreat from legal justification, they suggest, may come with significant costs for the international order. While stretching international law can hollow out its substance, abandoning legal justification altogether undermines its normative authority as a framework of global governance. While legal hypocrisy, however problematic, signals that law still matters, legal silence treats it as optional.
Rethinking the decline of the liberal international order
These insights feed into a broader question that Dr Duroy is currently exploring: what helps explain the apparent weakening of the liberal international order, exemplified by the Trump administration’s neglect of international institutions? Rather than viewing this collapse as a result of states abandoning international law altogether, her research explores the possibility that it is partly the product of how international law has been used to legitimate controversial security practices — from expansive surveillance and cross-border assassinations to extreme uses of force. Rather than a sudden rupture, the recent U.S. turn away from legal justification may instead represent the endpoint of a longer trajectory in which law was increasingly used to normalise violence rather than restrain it.
Dr Duroy is continuing this line of inquiry as a fellow of the Hamburg Institute for Social Research, where she is part of the research hub, ‘Excessive State Power and State Killings in Democracies.’ Through this work, she aims to deepen our understanding of how democratic states justify violence and how these justificatory choices reshape the capacity of international law to constrain it in an increasingly unstable global order.
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