|The obligation of non-intervention, a norm of customary international law prohibits States from intervening coercively in the internal or external affairs of other States. Prohibited intervention was authoritatively defined by the International Court of Justice in the judgment on the merits in the 1986 case Nicaragua v United States:|
In order for an act, including a cyber operation, to qualify as a prohibited intervention, it must fulfil the following conditions:
A prohibited intervention must … be one bearing on matters in which each State is permitted, by the principle of State sovereignty, to decide freely. One of these is the choice of a political, economic, social and cultural system, and the formulation of foreign policy. Intervention is wrongful when it uses methods of coercion in regard to such choices, which must remain free ones.
- The act must bear on those matters in which States may decide freely. The spectrum of such issues is particularly broad and it includes both internal affairs (such as “choice of a political, economic, social, and cultural system”), and external affairs (“formulation of foreign policy”)—the so-called domaine réservé of States. The content of the domaine réservé is determined by the scope and nature of the state's international legal obligations.
- The act must be coercive in nature. There is no generally accepted definition of “coercion” in international law. However, in the cyber context, the Tallinn Manual 2.0 suggests that “the coercive effort must be designed to influence outcomes in, or conduct with respect to, a matter reserved to a target State”. On that basis, the “key is that the coercive act must have the potential for compelling the target State to engage in an action that it would otherwise not take (or refrain from taking an action it would otherwise take)”. This approach distinguishes coercing or compelling the target State from merely influencing it by persuasion or propaganda and from causing nuisance without any particular goal. The element of coercion also entails the requirement of intent.
- Finally, there has to be a causal nexus between the coercive act and the effect on the internal or external affairs of the target State.