Retorsion: An Underrated Retaliatory Measure Against Malign Cyber Operations

The articles discusses the application of the concept of retorsion in relation to defensive measures against hostile cyber operations. Retorsion is a concept not regulated by international law, which gives the victim state a high degree of flexibility in its use. However, its limits are formed by the rules of international law (retorsion is an unfriendly act not prohibited by international law). The paper is divided into three main parts. The first part discusses the concept of retorsion in general terms and its relation to cyber operations, the second part defines the relationship between retorsion, countermeasures, plea of necessity and the right of self-defence, and the third part consists of in-depth analysis of states’ practice. The analysis of states’ practices includes both the actual measures that states have taken in response to cyber operations (e.g. expulsion of diplomats, economic sanctions, travel bans) and official statements on the issue that have been published, particularly in the period 2019–2022. Attention is also paid to the possibilities of using retorsion against cyber operations carried out by non-state actors.