Self-defence

Definition

Self-defence

A State may respond with force to a cyber operation that qualifies as an “armed attack” pursuant to the customary right to self-defence, as codified in Article 51 of the UN Charter. Most commentators consider only grave uses of force – typically, those that kill or injure persons or damage or destroy property – to constitute armed attacks. The United States, however, takes an outlier position, consistently arguing that any illegal use of force gives rise to the use of force in self-defence. In Nicaragua, the ICJ identified “scale and effects” as criteria upon which to judge whether a use of force constitutes an armed attack. In the Court’s view, only “the most grave” uses of force do so. Thus, only cyber operations that seriously injure or kill a number of persons or cause significant damage to, or destruction of, property would undoubtedly constitute armed attacks.

National positions

United Kingdom: 2021

"An operation carried out by cyber means may constitute an armed attack giving rise to the inherent right of individual or collective self-defence, as recognised in Article 51 of the UN Charter where the scale and effects of the operation are equivalent to those of an armed attack using kinetic means. Factors in considering the scale and effects of an attack may include the (actual or anticipated) physical destruction of property, injury and death. The exercise of the inherent right of self-defence against an imminent or on-going armed attack whether by kinetic or cyber means, may itself be by cyber or kinetic means and must always fulfil the requirements of necessity and proportionality. Whether or not to have recourse to the exercise of the inherent right of self-defence will always be carefully considered having regard to all the circumstances."

United States of America: 2012

"A state’s national right of self-defense, recognized in Article 51 of the UN Charter, may be triggered by computer network activities that amount to an armed attack or imminent threat thereof. As the United States affirmed in its 2011 International Strategy for Cyberspace, “[w]hen warranted, the United States will respond to hostile acts in cyberspace as we would to any other threat to our country.”

"[...]the United States has for a long time taken the position that the inherent right of self-defense potentially applies against any illegal use of force. In our view, there is no threshold for a use of deadly force to qualify as an “armed attack” that may warrant a forcible response. But that is not to say that any illegal use of force triggers the right to use any and all force in response—such responses must still be necessary and of course proportionate. We recognize, on the other hand, that some other countries and commentators have drawn a distinction between the “use of force” and an “armed attack,” and view “armed attack”—triggering the right to self-defense—as a subset of uses of force, which passes a higher threshold of gravity."

Appendixes

See also

• Scenario 14: Ransomware campaign