The Plea of Necessity in Cyber Emergencies Unresolved Doctrinal Questions

Abstract Although an increasing number of states has explicitly acknowledged the plea of necessity as a circumstance precluding wrongfulness to be applicable in situations of cyber emergencies, important doctrinal questions remain underexposed in both official expressions of opinio juris and in the literature. The article closes this gap by giving an account of three of the most salient issues in the context of the necessity defence: the “only way” requirement, the condition of non-contribution, and assistance by unaffected states to defensive measures taken in emergencies. It concludes that while recently growing academic criticism of the prevailing strict understanding of the “only way” criterion might be less relevant in the cyber context, states should consider more explicitly how emerging norms obliging states to observe a certain standard of cyber hygiene in regard to domestic cyber infrastructures could influence legal assessments as to a possible contribution to a situation of cyber emergency, potentially precluding the necessity defence. Finally, long-running doctrinal debates surrounding the exact legal nature of the defence within the larger context of the customary rules on state responsibility are revisited to examine whether third states could be permitted to come to the help of imperilled states even if the defence does not apply to them individually.