Abstract
The advent and proliferation of State-sponsored cyber operations, especially low-intensity cyber campaigns producing effects short of destruction and injury, seem likely to augment the importance of non-intervention as a legal means of maintaining international peace and respect for sovereignty. This article highlights obstacles to the operation of the principle. As presently understood, the customary international law principle of non-intervention includes significant doctrinal gaps and ambiguities. In particular, States have not achieved or expressed consensus on a notion of coercion sufficient to deter or regulate acts of intervention in cyberspace. Additionally, States have not mustered, in the context of cyberspace, sufficiently clear notions of the internal and external matters protected by the principle's customary prohibition.This article advocates deliberate State attention to these troubling ambiguities and highlights the principle of non-intervention as an essential legal aspect of States' peaceful coexistence in cyberspace.