The application of international law to state cyberattacks

This report from the UK think tank Chatham House looks at the application of the sovereignty and non-intervention principles of international law to state cyberattacks.

Hostile cyber operations by one state against another state are increasingly common. This paper analyzes the application of the sovereignty and non-intervention principles in relation to states’ cyber operations in another state below the threshold of the use of force. The vast majority of state-to-state cyberattacks consist of persistent, low-level intrusions that take place below the threshold of use of force. International law, including the principle of non-intervention in another state’s internal affairs and the principle of sovereignty, applies to these cyber operations. It is not clear whether any unauthorized cyber intrusion would violate the target state’s sovereignty, or whether there is a threshold in operation. While some would like to set limits by reference to effects of the cyber activity, at this time such limits are not reflected in customary international law.

The assessment of whether sovereignty has been violated therefore has to be made on a case by case basis, if no other more specific rules of international law apply. In due course, further state practice and opinio iuris may give rise to an emerging cyber-specific understanding of sovereignty, just as specific rules deriving from the sovereignty principle have crystallized in other areas of international law. Before a principle of due diligence can be invoked in the cyber context, further work is needed by states to agree upon rules as to what might be expected of a state in this context. The principle of non-intervention applies to a state’s cyber operations as it does to other state activities. It consists of coercive behaviour by one state that deprives the target state of its free will in relation to the exercise of its sovereign functions in order to compel an outcome in, or conduct with respect to, a matter reserved to the target state. In practice, activities that contravene the non-intervention principle and activities that violates sovereignty will often overlap.

In order to reach agreement on how international law applies to states’ cyber operations below the level of use of force, states should put their views on record, where possible giving examples of when they consider that an obligation may be breached, as states such as the UK, Australia, France and the Netherlands have done. Further discussion between states should focus on how the rules apply to practical examples of state-sponsored cyber operations. There is likely to be more commonality about specific applications of the law than there is about abstract principles. The prospects of a general treaty in this area are still far off. In due course, there may be benefit in considering limited rules, for example on due diligence and a prohibition on attacking critical infrastructure, before tackling broad principles.

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