Prohibition of intervention

Definition
The obligation of non-intervention established by customary international law prohibits States from intervening 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:"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."Two elements follow from this understanding. The first is that in order for an act (a term that is wide enough to include a cyber operation) to qualify as prohibited intervention, it must bear on those matters in which States are allowed to decide freely (the so-called domaine réservé of States). As the ICJ ruling explains, the spectrum of such issues is particularly broad and it includes choices of political, economic, social, and cultural nature. For instance, the organization and conducting of domestic elections certainly counts among such choices, given that the result of the process is the appointment of the head of State or the composition of the parliament.

The second element of prohibited intervention is that the act in question must be coercive in nature. There is no generally accepted definition of “coercion” in international law. However, as per the analysis in the Tallinn Manual 2.0, 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)”. Therefore, whether this element is met depends on the specific circumstances of each case.

Attributing the conduct to a State different from State A is a necessary prerequisite for qualifying it as a breach of the prohibition of non-intervention. Non-State actors cannot violate sovereignty on their own. For further details, refer to General matters 001: Attribution.

Every breach of the prohibition of non-intervention constitutes a violation of sovereignty and an internationally wrongful act, and can justify a response from the target State according to the law of State responsibility, such as countermeasures, if further conditions are met. For further details, refer to General matters 002: Countermeasures.

Prohibited intervention (conditions)


Bibliography and further reading

 * MN Schmitt (ed), Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations (CUP 2017)
 * Etc.