National position of the United Kingdom (2018)


This is the national position of the United Kingdom on international law applicable to cyberspace. The position has been presented by the UK Attorney General Jeremy Wright on 23 May 2018 during a Chatham House speech titled “Cyber and International Law in the 21st Century”. [1]

Applicability of international law

“Cyber space is not – and must never be – a lawless world. It is the UK’s view that when states and individuals engage in hostile cyber operations, they are governed by law just like activities in any other domain. The UK has always been clear that we consider cyber space to be an integral part of the rules based international order that we are proud to promote. The question is not whether or not international law applies, but rather how it applies and whether our current understanding is sufficient.

What this means is that hostile actors cannot take action by cyber means without consequence, both in peacetime and in times of conflict. States that are targeted by hostile cyber operations have the right to respond to those operations in accordance with the options lawfully available to them and that in this as in all things, all states are equal before the law.”[2]


“[..]a further contested area amongst those engaged in the application of international law to cyber space is the regulation of activities that fall below the threshold of a prohibited intervention, but nonetheless may be perceived as affecting the territorial sovereignty of another state without that state’s prior consent. Some have sought to argue for the existence of a cyber specific rule of a “violation of territorial sovereignty” in relation to interference in the computer networks of another state without its consent. Sovereignty is of course fundamental to the international rules-based system. But I am not persuaded that we can currently extrapolate from that general principle a specific rule or additional prohibition for cyber activity beyond that of a prohibited intervention. The UK Government’s position is therefore that there is no such rule as a matter of current international law.[3]

State responsibility

“There are obviously practical difficulties involved in making any attributions of responsibilities when the action concerned is capable of crossing traditional territorial boundaries and sophisticated techniques are used to hide the identity and source of the operation. Those difficulties are compounded by the ready accessibility of cyber technologies and the resultant blurring of lines between the actions of governments and those of individuals.

The international law rules on the attribution of conduct to a state are clear, set out in the International Law Commissions Articles on State Responsibility, and require a state to bear responsibility in international law for its internationally wrongful acts, and also for the acts of individuals acting under its instruction, direction or control.”[4]


“These principles must be adapted and applied to a densely technical world of electronic signatures, hard to trace networks and the dark web. They must be applied to situations in which the actions of states are masked, often deliberately, by the involvement of non-state actors. And international law is clear – states cannot escape accountability under the law simply by the involvement of such proxy actors acting under their direction and control.”


“As with other forms of hostile activity, there are technical, political and diplomatic considerations in publicly attributing hostile cyber activity to a state, in addition to whether the legal test is met.

There is no legal obligation requiring a state to publicly disclose the underlying information on which its decision to attribute hostile activity is based, or to publicly attribute hostile cyber activity that it has suffered in all circumstances.

However, the UK can and does attribute malicious cyber activity where we believe it is in our best interests to do so, and in furtherance of our commitment to clarity and stability in cyberspace. Sometimes we do this publicly, and sometimes we do so only to the country concerned. We consider each case on its merits.

For example, the WannaCry ransomware attack affected 150 countries, including 48 National Health Service Trusts in the United Kingdom. It was one of the most significant attacks to hit the UK in terms of scale and disruption. In December 2017, together with partners from the US, Australia, Canada, New Zealand, Denmark and Japan, we attributed the attack to North Korean actors. Additionally, our attribution, together with eleven other countries, of the destructive NotPetya cyber-attack against Ukraine to the Russian government, specifically the Russian Military in February this year illustrated that we can do this successfully. If more states become involved in the work of attribution then we can be more certain of the assessment. We will continue to work closely with allies to deter, mitigate and attribute malicious cyber activity. It is important that our adversaries know their actions will be held up for scrutiny as an additional incentive to become more responsible members of the international community.”[5]


“Consistent with the de-escalatory nature of international law, there are clear restrictions on the actions that a victim state can take under the doctrine of countermeasures. A countermeasure can only be taken in response to a prior internationally wrongful act committed by a state, and must only be directed towards that state. This means that the victim state must be confident in its attribution of that act to a hostile state before it takes action in response. In cyberspace of course, attribution presents particular challenges, to which I will come in a few moments. Countermeasures cannot involve the use of force, and they must be both necessary and proportionate to the purpose of inducing the hostile state to comply with its obligations under international law.

These restrictions under the doctrine of countermeasures are generally accepted across the international law community. The one area where the UK departs from the excellent work of the International Law Commission on this issue is where the UK is responding to covert cyber intrusion with countermeasures.

In such circumstances, we would not agree that we are always legally obliged to give prior notification to the hostile state before taking countermeasures against it. The covertness and secrecy of the countermeasures must of course be considered necessary and proportionate to the original illegality, but we say it could not be right for international law to require a countermeasure to expose highly sensitive capabilities in defending the country in the cyber arena, as in any other arena.

In addition, it is also worth stating that, as a matter of law, there is no requirement in the doctrine of countermeasures for a response to be symmetrical to the underlying unlawful act. What matters is necessity and proportionality, which means that the UK could respond to a cyber intrusion through non-cyber means, and vice versa.”[6]

Prohibition of intervention

“In certain circumstances, cyber operations which do not meet the threshold of the use of force but are undertaken by one state against the territory of another state without that state’s consent will be considered a breach of international law.

The international law prohibition on intervention in the internal affairs of other states is of particular importance in modern times when technology has an increasing role to play in every facet of our lives, including political campaigns and the conduct of elections. As set out by the International Court of Justice in its judgment in the Nicaragua case, the purpose of this principle is to ensure that all states remain free from external, coercive intervention in the matters of government which are at the heart of a state’s sovereignty, such as the freedom to choose its own political, social, economic and cultural system.

The precise boundaries of this principle are the subject of ongoing debate between states, and not just in the context of cyber space. But the practical application of the principle in this context would be the use by a hostile state of cyber operations to manipulate the electoral system to alter the results of an election in another state, intervention in the fundamental operation of Parliament, or in the stability of our financial system. Such acts must surely be a breach of the prohibition on intervention in the domestic affairs of states.”[7]

International humanitarian law (jus in bello)

“[..]in addition to the provisions of the UN Charter, the application of international humanitarian law to cyber operations in armed conflicts provides both protection and clarity. When states are engaged in an armed conflict, this means that cyber operations can be used to hinder the ability of hostile groups such as Daesh to coordinate attacks, and in order to protect coalition forces on the battlefield. But like other responsible states, this also means that even on the new battlefields of cyber space, the UK considers that there is an existing body of principles and rules that seek to minimise the humanitarian consequences of conflict.”[8]

Self-defence, armed attack and use of force

First, there is the rule prohibiting interventions in the domestic affairs of states both under Article 2(7) of the Charter and in customary international law. This prohibition means that any activity in cyber space which reaches the level of such an intervention is unlawful. Any activity of this nature by a state could only become permissible in response to some prior illegality by another state.

The next relevant provision of the UN Charter is in Article 2(4) which prohibits the threat or use of force against the territorial independence or political integrity of any state. Any activity above this threshold would only be lawful under the usual exceptions – when taken in response to an armed attack in self-defence or as a Chapter VII action authorised by the Security Council. In addition, the UK remains of the view that it is permitted under international law, in exceptional circumstances, to use force on the grounds of humanitarian intervention to avert an overwhelming humanitarian catastrophe.

Thirdly, the UK considers it is clear that cyber operations that result in, or present an imminent threat of, death and destruction on an equivalent scale to an armed attack will give rise to an inherent right to take action in self- defence, as recognised in Article 51 of the UN Charter.

If a hostile state interferes with the operation of one of our nuclear reactors, resulting in widespread loss of life, the fact that the act is carried out by way of a cyber operation does not prevent it from being viewed as an unlawful use of force or an armed attack against us. If it would be a breach of international law to bomb an air traffic control tower with the effect of downing civilian aircraft, then it will be a breach of international law to use a hostile cyber operation to disable air traffic control systems which results in the same, ultimately lethal, effects.

Acts like the targeting of essential medical services are no less prohibited interventions, or even armed attacks, when they are committed by cyber means.”[9]


See also

National position of the United Kingdom (2021)

Notes and references

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