States' Discourse on Third-Party and Collective Countermeasures in Cyberspace: An Evolution of Opinio Juris on Countermeasures by Non-Injured States?

Abstract

This article examines the positions expressed by states on countermeasures carried out by noninjured states in cyberspace. This is currently an important matter of discussion among states and scholars alike. In May 2019, Estonian President Kersti Kaljulaid made a statement in favour of collective countermeasures in cyberspace. Since then, ten other states have spoken, taking different positions. Third-party countermeasures and collective countermeasures are often confused, if not conflated, in the statements of some states and in part of the scholarship. In general, the debate underlines the unfairness of the non-permissibility of collective countermeasures, especially where those states that have fewer capabilities and expertise or whose capabilities are already absorbed by the fight against the initial internationally wrongful cyber operation are prevented from benefitting from the capabilities and expertise of another state. The parallel between the right to collective self-defence and the plea for a right to collective countermeasures is often highlighted. This article examines the different positions and arguments expressed, as well as the specificities of the debate on collective countermeasures in cyberspace. It interrogates the relationship between the different positions and how this may impact the evolution of the opinio juris of the concerned states and the development of customary international law.