Scenario 14: Ransomware campaign
Municipal governments and health care providers in one State fall victim to a ransomware campaign launched by a non-State group in a second State. The ransomware campaign disables municipal and health care services in the first State. The scenario explores how the ransomware campaign may be classified under international law. It first considers whether the campaign is a breach of an international obligation attributable to a State. It then discusses the possible legal responses available to the victim State.
- 1 Scenario
- 2 Legal analysis
- 2.1 Attribution
- 2.2 Breach of an international obligation
- 2.3 Permissible responses by State A
- 3 Checklist
- 4 Appendixes
Attribution, cyber operation, due diligence, prohibition of intervention, ransomware, retorsion, sovereignty, State responsibility, use of force
[F1] A previously unknown strain of ransomware is directed toward several municipal governments and a variety of health care services providers in State A through the use of phishing emails. Upon opening the emails by government and health care services employees, computer systems are affected. In a major metropolitan city in State A, the local court is forced offline because the ransomware has encrypted its computer systems and the police are forced to revert to using pen and paper to issue traffic citations. Morever, police are unable to effectuate warrants and ongoing investigations into crimes must be postponed. Thousands of computers at the State A Department of Transportation stop working. Processing of applications for drivers’ licenses and permit renewals is halted. City authorities refuse to pay ransom to the attackers and are forced to spend considerable sums to repair and restore the affected computer systems.
[F2] The same ransomware infects hospital systems in a separate city in State A. Doctors are unable to access patient data stored digitally. Staff resort to using paper charts, transmitting messages in person and being able to perform only basic treatment without access to X-rays or ultrasound scans. Health records system of a major company incorporated in State A is also infected, leaving thousands of patient medical files inaccessible. The inaccessibility of patient data coupled with the disruption to the hospital computer systems results in the inability of the medical staff to perform critical surgeries. Patients are admitted to the emergency rooms when absolutely necessary, but cannot be operated on in a timely manner, resulting in several otherwise preventable injuries, but fortunately no loss of life. Lesser harm is caused to patients who cannot be given necessary medication because their medical records are inaccessible. A significant economic loss is caused by the need to reroute patients to other hospitals.
[F3] After several weeks, the ransomware attacks stop.
[F4] Authorities in State A determine that the ransomware was created by a group of hackers in State B. The hackers’ relationship to State B is not clear. However, the methodology utilized by the hackers bears a striking similarity to a previous cyber operation attributed to State B. Moreover, State B, while formally denying any involvement in the incidents, praises the actions of the hackers as a just and foreseeable reaction to what State B characterizes as State A’s foreign policy misdeeds. State A and State B have strained relations.
[F5] State A indicts the hackers, but State B does not cooperate in extraditing the hackers to State A for prosecution under criminal laws of State A for several reasons. Firstly, State B is prohibited by its constitution from extraditing its citizens for criminal prosecution in other States. Secondly, relations between State A and State B are such that, even in the absence of the foregoing reasons, State B would be disinclined to co-operate with State A. Finally, State media in State B has lauded the actions of the hackers as a just response to State A’s purported misdeeds.
- Sony Pictures Entertainment attack (2014)
- SamSam ransomware attack (2018)
- WannaCry (2017)
- NotPetya (2017)
- Texas Municipality ransomware attack (2019)
2 Legal analysis
For a general overview of the structure of analysis in this section, see Note on the structure of articles.
[L1] The analysis in this scenario focuses on the legal qualification of the ransomware attacks from the perspective of international law. In particular, it examines whether the relevant conduct is attributable to State B and whether it amounts to a breach of an international obligation owed by State B to State A. It then discusses the possible legal responses available to the State A.
|State organs and persons and entities in exercise of governmental authority|
Such conduct is attributable to the State even if the organ, person or entity acting in that capacity "exceeds its authority or contravenes instructions" (acts ultra vires).
[L2] It is not clear that the hackers are a State organ of State B, nor that they are exercising governmental authority on behalf of State B.
2.1.2 Non-State actors
[L3] As non-State actors, the actions of the hackers may be attributable to State B if they were acting under the instructions or effective control of State B or if State B acknowledges and adopts the actions as its own. First, with regard to the instructions or effective control standard, there is no evidence to suggest that the hackers were operating under the instructions or effective control of State B. Likewise, there is insufficient evidence to indicate that State B adequately acknowledged and adopted the behaviour of the hackers as its own. Although State B, including its State media, praised the actions of the hackers as a just and foreseeable reaction to what State B characterizes as State A’s foreign policy, this is unlikely to satisfy the acknowledgment and adoption standard which is applied narrowly and requires more State involvement that mere endorsement or expression of approval. Moreover, a minority view holds that the acknowledgement and adoption standard only applies prospectively, and, thus, under this view, State B’s praise of the actions of the hackers after the fact would not suffice to meet the standard.
2.2 Breach of an international obligation
[L4] This section considers whether the ransomware attacks are a breach of an international obligation—specifically, the prohibition on the use of force, the prohibition on intervention, the obligation to respect the sovereignty of other States, and the duty of due diligence.
2.2.1 Use of force
|Use of force|
| This prohibition is reflective of customary international law and it is frequently described as a peremptory norm of international law. However, the notion of “force” in this context is limited to armed force, and to operations whose scale and effects are comparable to the use of armed force.
At present, there is a debate as to whether cyber operations with no physical effects may amount to a prohibited use of force. It has been argued that disruptive cyber operations of this kind fall under the scope of Article 2(4) if the resulting disruption is “significant enough to affect state security”. Undoubtedly, one of the purposes of the prohibition of force under international law is to safeguard the national security of the potentially affected States. However, many forms of outside interference including various forms of political and economic coercion may affect the national security of the victim State. And yet, the drafters of the UN Charter had expressly rejected the proposal to extend the prohibition of force beyond the strict confines of military (or armed) force. This is reflected also in the preamble, which explicitly stipulates that the drafters sought “to ensure, by the acceptance of principles and the institution of methods, that armed force shall not be used, save in the common interest”.
In principle, it could be argued that the notion of “force”, like other generic terms in treaties of unlimited duration, should be presumed to have an evolving meaning.
As of 2020, there is limited State practice supporting the claim that the meaning of “force” has evolved to include non-destructive cyber operations against critical national infrastructure and no victim State of an operation of this kind has suggested that the operation would have amounted to a use of force. However, States have begun addressing this question. In particular, France and the Netherlands allow for the possibility of cyber operations, which do not produce physical effects, to qualify as uses of force, if certain criteria are met. These criteria include the seriousness and reach of a given cyber operation’s consequences and its military nature, as well as “the circumstances prevailing at the time of the operation, such as the origin of the operation and the nature of the instigator (military or not), the extent of intrusion, the actual or intended effects of the operation or the nature of the intended target”. Several of these criteria are also reflected in the Tallinn Manual 2.0.
Even if an operation does not meet the threshold of the use of force, it may still be considered a violation of other rules of international law. In this regard, the prohibition of non-intervention, the obligation to respect the sovereignty of other States, and the possible obligation to refrain from launching cyber operations against other States’ critical infrastructure are all of potential relevance.
[L5] It is unlikely that the ransomware attacks amount to a use of force. A following consideration of eight factors — severity, immediacy, directness, invasiveness, measurability of effects, military character, State involvement, and presumptive legality — shows that to be so. However, the eight factors do not constitute an official framework that must be used when assessing the threshold of use of force, but rather are similar factors that States are likely to consider.
[L6] Crucially, the ransomware attacks’ overall severity was significant. While the disruption in municipal functions caused only inconvenience for citizens and municipal agencies, the harm that resulted from the disruption to medical services was significant. Several patients admitted to hospitals in State A for emergency procedures were unable to be operated on in a timely manner, in several instances resulting in otherwise preventable injury.
[L7] The consequences of the ransomware attacks did not follow immediately from the cyber activities. In most cases, the penetration of the affected systems occurred weeks before the ransom notice was directed to the victim, and monetary costs incurred by the victims to recover data and restore their systems followed weeks or months thereafter. States are more likely to view a cyber operation that causes immediate consequences as a use of force, as distinguishable from consequences that are delayed or manifest slowly over time. Likewise, the less opportunity a State has to mitigate or forestall the effects of a cyber operation, the more likely it is that the operation will be considered as a use of force. State A, in fact, had the choice, of making a ransom payment and thus preventing the consequences of the attacks.
[L8] The effects of the ransomware attacks on State A were not directly connected to the underlying cyber activity. Directness depends on the degree of attenuation between the initial act and its consequences. The initial act in this case was the sending of phishing emails. When those emails were mistakenly opened, the ransomware infected the recipient’s computers. Computer files were then encrypted and rendered inaccessible. Because the victims failed to make ransom payments, the files were not readily decrypted. Inability to access the files ultimately and indirectly resulted in harm to the victim organizations. While the attacks did have indirect consequences, in the form of the costs incurred to restore backed-up data and to implement improved security, the degree of attenuation between the initial act and its consequences means that directness of the attacks’ cause and effects may not be viewed as comparable to the direct harm caused to people or objects by a kinetic attack.
[L9] The hackers did indeed invasively probe the networks of municipal governments and healthcare providers; however, these were not top-secret networks that were necessarily intended to have the highest level of security. And the networks that the hackers did access were not amongst the most secure maintained by the victims: for instance, emergency response networks were untouched. The effects of the ransomware attacks cannot be calculated with certainty, even if a numerical sum can be affixed to the remediation costs.
[L10] There is no suggestion that the attacks had a military character. No link has been established between the hackers and the military of State B or of any other State. Nor were the military forces of State A the target of the ransomware campaign.
[L11] Likewise, no State is publicly alleged to have been involved, either directly or indirectly, in the campaign.
[L12] Finally, the reconnaissance and network probing activities of the hackers were qualitatively similar to espionage activities, which are not per se regulated under international law and are not presumptively judged to be uses of force.
[L13] In consideration of each one of the foregoing factors, severity is the only factor that could feasibly cause the ransomware attacks to meet the criteria of a use of force. However, severity is a subject to a de minimis rule. It is likely that the severity of the ransomware attacks was not sufficient to meet that de minimis. While the otherwise preventable injuries to persons are certainly more than mere inconveniences, it is unclear whether the limited number of injuries, in light of the ransomware attacks’ failure to meet any of the other criteria, renders the attacks so severe as to constitute a use of force. However, scholars and States may reach different conclusions in their assessment.
2.2.2 Prohibition of intervention
|Prohibition of intervention|
|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:
[L14] There is no suggestion that the ransomware attacks in any way involved the external affairs of State A, but certain effects of the ransomware did implicate the domaine réservé of State A. For example, the conduct of traffic police or the operation of the Department of Transportation are certainly fields of activity not committed to international law but possibly form part of the domaine réservé of State A.
[L15] It is less likely that the attacks were coercive efforts designed to influence outcomes in those fields of activity. While the hackers may have manipulated hospitals in State A and the municipal government of a city in State A into making a choice between paying a ransom or spending considerably more to remedy the effects, that choice was not coercive in the sense that it was designed to compel the State A to adopt a particular policy with regard to traffic, policing, hospitals, or municipal policy. Instead, the coercion was intended to compel the payment of ransom.
[L16] Accordingly, the ransomware attacks would likely not be considered a coercive intervention in the domaine réservé of State A.
2.2.3 Obligation to respect the sovereignty of other States
|Sovereignty is a core principle of international law. According to a widely accepted definition of the term in the 1928 Island of Palmas arbitral award,|
Multiple declarations by the UN, NATO, OSCE, the European Union, and individual States have confirmed that international law applies in cyberspace. Accordingly, so too does the principle of sovereignty. However, there is some debate as to whether this principle operates as a standalone rule of international law, the breach of which gives rise to state responsibility.
The remainder of this section proceeds on the basis of the former “sovereignty-as-rule” approach. Those espousing the latter “sovereignty-as-principle” approach should refer to other relevant sections of the legal analysis (such as that on the prohibition of intervention).
It is understood that sovereignty has both an internal and an external component. In the cyber context, the “internal” facet of sovereignty entails that “[a] State enjoys sovereign authority with regard to the cyber infrastructure, persons, and cyber activities located within its territory, subject to its international legal obligations.”
As a general rule, each State must respect the sovereignty of other States. It is clear that a cyber operation with severe destructive effects, comparable to a “non-cyber” armed attack or a use of force against a State, constitutes a violation of its sovereignty; however, with more subtle cyber operations, the question is far from settled.
The following modalities, highlighted in the Tallinn Manual 2.0, represent different ways of determining what a “sovereignty violation” might mean in the context of cyber operations:
The Tallinn Manual’s view of what constitutes a violation of sovereignty has been expressly endorsed by one State: the Netherlands. An alternative test has been proposed by France, which argues that a breach of sovereignty occurs already when there is “any unauthorised penetration by a State of [the victim State’s] systems”.
Attributing the relevant cyber operation to a State different from the target State is a necessary prerequisite for qualifying the cyber operation as a violation of the target State's sovereignty.
Whether non-State actors can violate territorial sovereignty on their own is a matter of disagreement.
[L17] The attacks caused injury to persons, and they resulted in severe losses of functionality. Everything from normal employee workstations at the Department of Transportation to sophisticated surgical systems and diagnostic equipment at the hospital were unable to function. Medical services were disrupted. Municipal offices were forced offline for weeks. The loss of functionality required spending considerable sums of money on IT support and reinstallation of software to remediate.
[L18] Moreover, the ransomware attacks also interfered with the performance of inherently governmental functions. The court and police operations of State A’s cities are inherently governmental functions, which although not usurped were certainly the subject of interference.
[L19] Thus, provided the ransomware attacks were attributable to State B (on which, see above), they would likely amount to a violation of the State A’s sovereignty.
2.2.4 Due diligence obligation
| In the cyber context, the UN General Assembly urged States already in 2000 to “ensure that their laws and practice eliminate safe havens for those who criminally misuse information technologies”.
It is the matter of some controversy whether the principle of due diligence reflects a binding obligation applicable to cyber operations. It has also been proposed that in the cyber context, it is preferable to construe due diligence as a standard of attribution rather than as a standalone primary rule of international law. Nevertheless, the present analysis proceeds on the basis that as a matter of lex lata, due diligence constitutes a general international obligation for every State not to knowingly allow its territory to be used for internationally wrongful acts using cyber means. This view has also been endorsed by several States, including Australia, Czech Republic, Estonia, Finland, France, and the Netherlands.
[L20] Breaches of the duty of due diligence do not require that the act in question be attributable to a State. Instead, the duty of due diligence assumes the role of three parties: the target State toward which the cyber operation is directed; the territorial State; and a third-party author of the cyber operation. The third party may be another State, a non-State group, or a private person. The threshold is whether the underlying act, if committed by the territorial State, would have violated a rule of international law (i.e., would have been considered an internationally wrongful act). While, in general, it is States, not individuals or private entities, that are able to violate international law, cyber operations carried out by individuals or private entities that nevertheless result in serious adverse consequences fall within a State’s due diligence obligation.
[L21] Thus, if State B has knowledge of the hackers’ operations, those operations affect the rights of and cause serious adverse consequences to State A, and State A intimates that State B take action to stop the interference in its internal affairs, State B has a duty to take feasible action to stop the ransomware attacks. While the harm caused by a cyber activity must be serious, the due diligence principle does not require that there be physical damage to objects or injuries to persons.
[L22] The ransomware attacks affected State A’s sovereign right to perform inherently governmental functions—operating courts and police departments. Moreover, the attacks caused serious adverse consequences. The loss of functionality in hospital equipment caused injury to patients, and the encryption of health records led to improper medical care resulting in injury to patients.
[L23] Knowledge, actual and constructive, is a constitutive element of the duty of due diligence. A State is in breach even if it is unaware of cyber activity conducted from its territory but “objectively should have known that its territory was being used.” State A believes that State B knew that the hackers were operating from its territory. State B, on the other hand, argues that it had no such knowledge. It is not reasonable to assert that State B objectively should have known that the hackers were utilizing its cyber infrastructure to launch attacks against State A because the ransomware employed was complex and previously unknown. State B cannot be expected to prevent the use of malware of which is it entirely unaware. Given that the knowledge requirement was not met in this case, State B’s lack of response did not amount to a violation of its duty of due diligence.
2.3 Permissible responses by State A
[L24] Having established that the ransomware attacks do not meet the criteria of an internationally wrongful act, this section examines the options available for State B to take in response. Cyber operations may, in general, be met with four responses under international law: countermeasures, the plea of necessity, self-defense, and retorsion. For the reasons explained below, only retorsion is available to State A.
| Several States, including Austria, Estonia, France, Germany, Japan, the Netherlands, the United Kingdom, and the United States, have expressly confirmed the applicability of the law of countermeasures to cyber operations. Others, including Brazil, China, and Cuba, have expressed caution in this regard. Countermeasures should be distinguished from retorsions, which are unfriendly but lawful acts by the aggrieved party against the wrongdoer.
As a matter of general international law, an injured State may only take countermeasures against the responsible State if the following conditions are met:
Additionally, the countermeasures must fulfil the following requirements:
Taken countermeasures must be suspended if the internationally wrongful act has ceased or if “the dispute is pending before a court or tribunal which has the authority to make decisions binding on the parties”, and they must be terminated as soon as the responsible State has complied with its (secondary) obligations.
There is a debate as to whether States that have not themselves been directly injured by an unlawful cyber operation may engage in countermeasures in support of the injured State (sometimes referred to as collective countermeasures). In particular, one State has recently put forward the view that non-injured States “may apply countermeasures to support the state directly affected by the malicious cyber operation”. This would apply where diplomatic action is insufficient, but no lawful recourse to use of force exists. This interpretation would allow States to offer active assistance to States, which may not possess sufficient cyber capabilities themselves to counter an ongoing unlawful cyber operation. This view has found some support in scholarship, but was since rejected by at least one other State, with other parts of scholarship reluctant to endorse it. Therefore, it has to be regarded as a call for progressive development of international law, rather than a statement of the current state of international law.
Whether a particular measure fulfils these conditions is an objective question, while the burden of proof that the relevant conditions have been fulfilled falls on the injured State. The exact standard of proof required is unsettled in international law and it will depend on the relevant forum. However, relevant international jurisprudence tends to rely in this regard on the standard of “clear and convincing evidence”. This standard translates in practice into a duty to “convince the arbiter in question that it is substantially more likely than not that the factual claims that have been made are true.” Importantly, if a State does resort to countermeasures on the basis of an unfounded assessment that a breach has occurred, it may incur responsibility for its own wrongful conduct.
[L25] Countermeasures are not an available response to the ransomware attacks in the present scenario because the object of countermeasures must be a State, and, as seen above, it was not possible to attribute these ransomware attacks to a State. Moreover, there must be an internationally wrongful act to justify countermeasures. Even if there was one, countermeasures should be limited to ensuring that the unlawful act stops, potentially obtaining assurance and guarantees of non-repetition from the responsible State, and compelling the responsible State to make reparations. Because the ransomware incidents have stopped, countermeasures would have to be limited to compelling the responsible State to guarantee that the incidents do not resume and providing compensation for damages. Countermeasures may not be punitive or have a retaliatory effect.
[L26] State A would be advised to take precautions not to violate an obligation owed to a third State if engaging in countermeasures in response to the ransomware attacks even if they were attributable to State B because if the countermeasures were to violate a legal obligation owed to a third State, State A could itself be in breach of international law. The wrongfulness of such a breach is not precluded by the validity of the countermeasure against the responsible State. Thus, State A could find itself in breach of its international law obligations.
2.3.2 Plea of necessity
|Plea of necessity|
| Even then, the plea of necessity requires that the injured State’s action be balanced with the interests of any States that would be affected and with those of the international community. The injured State’s action must not seriously impair the essential interests of any other State. The plea of necessity is not available to injured States that have substantially contributed to the situation in which they find themselves. However, the plea of necessity can be asserted to take action against non-State actors and can justify actions that violate the rights of non-responsible States, if these conditions are met. In case the situation of necessity is caused by the conduct of non-State actors, attribution of this conduct to a State is not a precondition for acting based on the plea of necessity.|
[L27] A State’s “essential interest” is not clearly defined. It would certainly include healthcare, justice, and policing. Thus, the ransomware attacks on healthcare service providers and police and court systems certainly impaired essential interests of State A. It is unlikely that the temporary interruption in functionality the ransomware caused was sufficient to put those essential interests in grave and imminent peril. It is also unlikely that no other means existed to safeguard those interests. In any case, the ransomware attacks have abated, if temporarily, and the plea of necessity could only be invoked to end the harmful activity.
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.
[L28] The ransomware attacks did not amount to an armed attack. As discussed previously, the attacks were not even a use of force. Based on a consideration of following eight factors — severity, immediacy, directness, invasiveness, measurability of effects, military character, State involvement, and presumptive legality — the ransomware campaign is not at the level of a use of force (see above). Because the ransomware attacks failed to meet the criteria of use of force they could equally not amount to an armed attack triggering the right to self-defense. State A therefore has no right under international law to respond to the attacks with force.
|retorsion is “an unfriendly but nevertheless lawful act by the aggrieved party against the wrongdoer”. Such acts may include the prohibition of or limitations upon normal diplomatic relations, the imposition of trade embargoes or the withdrawal of voluntary aid programmes. Cyber-specific retorsions may include sending warnings to cyber operatives belonging to another State, observing the adversary’s cyber activities on one’s own network using tools such as “honeypots”, or slowing down malicious cyber operations conducted by other States.|
[L29] Retorsion is the only way for State A to respond to the ransomware campaign without a determination that another State B has breached an international obligation owed to it. State A is likely to view State B’s refusal to extradite or prosecute the attack’s perpetrators as an unfriendly act. State A may signal its displeasure at State B’s unfriendly action through common methods of retorsion such as expelling State B’s diplomats or imposing financial sanctions on State B.
- Can the ransomware attacks be attributed?
- Are the authors of the ransomware attack State organs or non-State organs exercising governmental authority?
- Are the authors of the ransomware attack non-State actors acting under the instructions or effective control of another State?
- Is the ransomware a use of force?
- What was the severity of the ransomware attacks?
- Did the effects of the ransomware attacks manifest immediately?
- Were the effects of the ransomware attacks directly connected to the underlying cyber activity?
- Did the ransomware attacks involve invasive penetration of top secret networks?
- Were the effects of the ransomware attacks measurable?
- Did the ransomware attacks have a military character?
- Was a State involved in carrying out or supporting the ransomware attacks?
- Are the ransomware attacks presumptively legal under international law?
- Is the ransomware a prohibited intervention?
- Did the ransomware campaign bear on the internal or external affairs of State A?
- Did the ransomware campaign coerce State A by depriving it of its freedom of choice concerning its internal or external affairs?
- Is the ransomware a violation of the targeted State’s sovereignty?
- Was the ransomware campaign conducted by a State organ of State B physically present on the territory of State A?
- Did the ransomware campaign result in physical damage or injury on State A’s territory?
- Did the ransomware campaign cause a loss of functionality of State A’s computer systems?
- Did the ransomware campaign interfere with State A’s inherently governmental functions?
- Due diligence
- If the ransomware attacks were committed by the territorial State, would they have violated a rule of international law?
- Did the territorial State have knowledge of the attacks?
- What responses are permissible?
- Is the object of countermeasures a State?
- Was an essential interest of the victim State in grave and imminent peril?
- Did the ransomware attacks constitute an armed attack, thus justifying resort to force in self-defense?
4.1 See also
- Due diligence
- Use of force
- Plea of necessity
- Prohibition of intervention
- Scenario 03: Cyber operation against the power grid
- Scenario 05: State investigates and responds to cyber operations against private actors in its territory
- Scenario 06: Cyber countermeasures against an enabling State
4.2 Notes and references
- ILC Articles on State Responsibility, Art 4(1).
- ILC Articles on State Responsibility, Art 6.
- ILC Articles on State Responsibility, Art 5.
- ILC Articles on State Responsibility, Art 7; Tallinn Manual 2.0, commentary to rule 15, paras. 6-7 and 12.
- ILC Articles on State Responsibility, Art 8; see also Kubo Mačák, ‘Decoding Article 8 of the International Law Commission’s Articles on State Responsibility: Attribution of Cyber Operations by Non-State Actors’ (2016) 21 JC&SL 405.
- ILC Articles on State Responsibility, Art 9.
- ILC Articles on State Responsibility, Art 10(1).
- ILC Articles on State Responsibility, Art 10(2).
- ILC Articles on State Responsibility, Art 11.
- ILC Articles on State Responsibility, Art 8.
- ILC Articles on State Responsibility, Art 11.
- Tallinn Manual 2.0, commentary to rule 17, para 16.
- Tallinn Manual 2.0, commentary to rule 17, para 18.
- Charter of the United Nations (adopted 26 June 1945, entered into force 24 October 1945) 1 UNTS 16 (UN Charter) art. 2(4).
- Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory (Advisory Opinion)  ICJ Rep 136, para 87; Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits)  ICJ Rep 14, paras 187–190.
- See, for example,The International Law Commission, 'Document A/6309/ Rev.1: Reports of the International Law Commission on the second part of its seventeenth and on its eighteenth session' Yearbook of the International Law Commission Vol. II (1966) 247 (“The law of the Charter concerning the prohibition of the use of force in itself constitutes a conspicuous example of a rule in international law having the character of jus cogens”); Christine Gray, International Law and the use of force (OUP 2018) 32; Oliver Corten, The Law against War (Hart Pub. 2010) 44; Oliver Dörr and Albrecgr Randelzhofer, ‘Article 2(4)’ in Bruno Simma et al (eds), The Charter of the United Nations: A Commentary Vol I (OUP 2012), 231, para 67 (“the prohibition of the use of force laid down in Art. 2 (4) is usually acknowledged in State practice and legal doctrine to have a peremptory character, and thus to be part of the international ius cogens”).
- Oliver Dörr and Albrecht Randelzhofer, ‘Article 2(4)’ in Bruno Simma et al (eds), The Charter of the United Nations: A Commentary Vol I (OUP 2012) 208 para 16 (“The term [‘force’] does not cover any possible kind of force, but is, according to the correct and prevailing view, limited to armed force.”).
- Cf. Ian Brownlie, International Law and the Use of Force by States (OUP 1963) 362 (“[Art 2(4)] applies to force other than armed force”); Tallinn Manual 2.0, rule 69 (“A cyber operation constitutes a use of force when its scale and effects are comparable to non-cyber operations rising to the level of a use of force.”).
- Marco Roscini, Cyber Operations and the Use of Force in International Law (OUP 2014) 55.
- Cf. Charter of the United Nations (adopted 26 June 1945, entered into force 24 October 1945) 1 UNTS 16 (UN Charter) art. 2(4) (expressly prohibiting the use of force against the “political independence” of any State).
- Documents of the United Nations Conference on International Organization (1945), vol VI, 334.
- Charter of the United Nations (adopted 26 June 1945, entered into force 24 October 1945) 1 UNTS 16 (UN Charter) preamble.
- Cf. Dispute regarding Navigational and Related Rights (Costa Rica v Nicaragua) Judgment [2009 ICJ Rep 213], para 66 (“[W]here the parties have used generic terms in a treaty, the parties necessarily having been aware that the meaning of the terms was likely to evolve over time, and where the treaty has been entered into for a very long period or is ‘of continuing duration’, the parties must be presumed, as a general rule, to have intended those terms to have an evolving meaning”).
- However, such claims are occasionally made in the scholarship: see, for example, Marco Roscini, Cyber Operations and the Use of Force in International Law (OUP 2014) 59; Nicholas Tsagourias 'Cyber Attacks, Self-Defence and the Problem of Attribution' (2012) 17 (2) Journal of Conflict and Security Law 23; Gary Brown and Keira Poellet, ‘The Customary International Law of Cyberspace’ (2012) Strategic Studies Quarterly 137.
- Dan Efrony and Yuval Shany, ‘A Rule Book on the Shelf? Tallinn Manual 2.0 on Cyberoperations and Subsequent State Practice’ (2018) 112 AJIL 583, 638.
- French Ministry of the Armies, ‘International Law Applied to Operations in Cyberspace’, 9 September 2019, at p. 7, stating that ‘France does not rule out the possibility that a cyberoperation without physical effects may also be characterised as a use of force’.
- Dutch Ministry of Foreign Affairs, ‘Letter to the parliament on the international legal order in cyberspace’ (5 July 2019) at p. 4, stating that ‘in the view of the government, at this time it cannot be ruled out that a cyber operation with a very serious financial or economic impact may qualify as the use of force’.
- Dutch Ministry of Foreign Affairs, ‘Letter to the parliament on the international legal order in cyberspace’ (5 July 2019) at p. 4.
- French Ministry of the Armies, ‘International Law Applied to Operations in Cyberspace’, 9 September 2019, at p. 7.
- Tallinn Manual 2.0, commentary to rule 69, para 9.
- Cf. US, State Department Legal Advisor Brian Egan, International Law and Stability in Cyberspace, Speech at Berkeley Law School (10 November 2016), 13 (“In certain circumstances, one State’s non-consensual cyber operation in another State’s territory could violate international law, even if it falls below the threshold of a use of force.”) (emphasis original); UK, Attorney General Jeremy Wright QC MP, Cyber and International Law in the 21st Century, Speech (23 May 2018) (“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.”).
- Tallinn Manual 2.0, commentary to rule 69, para 9.
- Tallinn Manual 2.0, commentary to rule 69, para 9.
- Tallinn Manual 2.0, commentary to rule 69, para 9.
- Tallinn Manual 2.0, commentary to rule 69, para 9. Most scholars agree that peacetime espionage is not the breach of an international obligation, but several have disagreed. See, e.g., Ingrid Delupis, Foreign Warships and Immunity for Espionage, 78 AM. J. INT’L L. 53, 67 (1984) (reasoning that peacetime espionage is illegal under international law if it involves an intrusion of foreign territory); Manuel R. Garcia-Mora, Treason, Sedition and Espionage as Political Offenses Under the Law of Extradition, 26 U. PITT. L. REV. 65, 79–80 (1964) (labeling peacetime espionage “an international delinquency and violation of international law”); Quincy Wright, Legal Aspects of the U-2 Incident, 54 AM. J. INT’L L. 836, 849 (1960) (stating that peacetimeespionage is an “illegitimate enterprise because [it] manifest[s] a lack of respect for foreign territory”).
- Tallinn Manual 2.0, commentary to rule 69, para 9.
- Military and Paramilitary Activities in and against Nicaragua (Nicaragua v US) (Merits)  ICJ Rep 14, para 205.
- Dutch Minister of Foreign Affairs, ‘Letter to the President of the House of Representatives on the International Legal Order in Cyberspace – Appendix: International Law in Cyberspace’ (5 July 2019), 3.
- See, for example, Katja Ziegler, “Domaine Réservé”, in Rudiger Wolfrum (ed), Max Planck Encyclopedia of Public International Law (OUP 2008) (updated April 2013) (defining the domaine réservé as those “areas where States are free from international obligations and regulation”).
- Tallinn Manual 2.0, commentary to rule 66, para 19.
- Tallinn Manual 2.0, commentary to rule 66, para 21; see also Dutch Minister of Foreign Affairs, ‘Letter to the President of the House of Representatives on the International Legal Order in Cyberspace – Appendix: International Law in Cyberspace’ (5 July 2019), 3.
- Tallinn Manual 2.0, commentary to rule 66, para 21.
- Tallinn Manual 2.0, commentary to rule 66, paras 19, 27.
- Tallinn Manual 2.0, commentary to rule 66, para 24 (The exact nature of the causal nexus was not agreed on).
- Tallinn Manual 2.0, commentary to rule 66, para 24.
- Island of Palmas (Neth. v. U.S.), 2 RIAA 829, 838 (Perm. Ct. Arb. 1928).
- UNGA Res 71/237 (30 December 2015) UN Doc A/RES/20/237.
- North Atlantic Treaty Organization, 'Wales Summit Declaration' (issued by the Head of State and Government participating in the meeting of the North Atlantic Council in Wales (5 September 2015) para 72.
- Organization for Security and Cooperation in Europe, Decision No. 1202, OSCE Confidence-Building Measures to Reduce the Risks of Conflict Stemming from the Use of Information and Communication Technologies (Permanent Council, 10 March 2016) PC.DEC/1202.
- Council of the European Union,"Council Conclusions on the Joint Communication to the European Parliament and the Council: Resilience, Deterrence and Defence: Building strong cybersecurity for the EU" (Council conclusions, 20 November 2017).
- Michael N Schmitt, 'Virtual Disenfranchisement: Cyber Election Meddling in the Grey Zones of International Law' (2018) 19 ChiJIntlL 30,40; Tallinn Manual 2.0, commentary to rule 4, para 2 (‘States shoulder an obligation to respect the sovereignty of other States as a matter of international law’).
- See Michael N Schmitt and Liis Vihul, ‘Respect for Sovereignty in Cyberspace’ (2017) 95 Tex L Rev. 1639, 1649 (noting that States ‘voiced no meaningful objection to Rule 4’ and that ‘it appeared to be received knowledge that a primary rule on territorial-sovereignty violations existed and applied to cyber operations.’).
- Austria, Pre-Draft Report of the OEWG - ICT: Comments by Austria (31 March 2020), stating that ‘a violation of the principle of State sovereignty constitutes an internationally wrongful act – if attributable to a State – for which a target State may seek reparation under the law of State responsibility’.
- Czech Republic, Statement by Mr. Richard Kadlčák, Special Envoy for Cyberspace, 2nd substantive session of the Open-ended Working Group on developments in the field of information and telecommunications in the context of international security (11 February 2020), stating that ‘[t]he Czech Republic concurs with those considering the principle of sovereignty as an independent right and the respect to sovereignty as an independent obligation.’
- French Ministry of the Armies, ‘International Law Applied to Operations in Cyberspace’, 9 September 2019, stating that ‘Any unauthorised penetration by a State of French systems or any production of effects on French territory via a digital vector may constitute, at the least, a breach of sovereignty’.
- Norbert Riedel, ‘Cyber Security as a Dimension of Security Policy’ (18 May 2015), arguing that ‘[e]ven in cases where one cannot speak of a use of force, the use of cyber capabilities might constitute a violation of sovereignty, if the attack can be attributed to a state, which then in turn could lead to consequences within the confines of public international law’.
- Iran, ‘Declaration of General Staff of the Armed Forces of the Islamic Republic of Iran Regarding International Law Applicable to the Cyberspace’ (July 2020), para. 4 (‘Any utilization of cyberspace if and when involves unlawful intrusion to the (public or private) cyber structures which is under the control of another state, maybe constituted as the violation of the sovereignty of the targeted state.’).
- Dutch Ministry of Foreign Affairs, ‘Letter to the parliament on the international legal order in cyberspace’ (5 July 2019), stating that ‘countries may not conduct cyber operations that violate the sovereignty of another country’.
- Gary P. Corn and Robert Taylor, ‘Sovereignty in the Age of Cyber’ (2017) 111 AJIL Unbound 207, 208 (arguing that sovereignty is ‘a principle of international law that guides state interactions’).
- Jeremy Wright, ‘Cyber and International Law in the 21st Century’ (23 May 2018) (stating that he was ‘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’); see also Memorandum from JM O’Connor, General Counsel of the Department of Defense, ‘International Law Framework for Employing Cyber Capabilities in Military Operations’ (19 January 2017) (considering that sovereignty is not ‘a binding legal norm, proscribing cyber actions by one State that result in effects occurring on the infrastructure located in another State, or that are manifest in another State’), as cited by Sean Watts & Theodore Richard, 'Baseline Territorial Sovereignty and Cyberspace' (2018) 22 Lewis & Clark L. Rev. 771, 829.
- Paul C. Ney, DOD General Counsel Remarks at U.S. Cyber Command Legal Conference, 2 March 2020, arguing that ‘the Department believes there is not sufficiently widespread and consistent State practice resulting from a sense of legal obligation to conclude that customary international law generally prohibits such non-consensual cyber operations in another State’s territory’.
- Cf. James Crawford, Brownlie's Principles of Public International Law (OUP 2012) 448.
- Tallinn Manual 2.0, rule 2.
- Sovereignty over cyber infrastructure derives from the traditional concept of sovereignty, independent of the use of cyberspace. See Wolff Heintschel von Heinegg, 'Territorial Sovereignty and Neutrality in Cyberspace' (2013) 89 Int’l L. Stud. 123 (noting that '[t]erritorial sovereignty [..] implies that, subject to applicable customary or conventional rules of international law, the State alone is entitled to exercise jurisdiction, especially by subjecting objects and persons within its territory to domestic legislation and to enforce these rules.')
- UN GA Res 2625 (XXV) (24 October 1970) (Friendly Relations Declaration), preamble (emphasizing “that the purposes of the United Nations can be implemented only if States enjoy sovereign equality and comply fully with the requirements of this principle in their international relations”); Tallinn Manual 2.0, rule 4.
- Tallinn Manual 2.0, commentary to rule 4, para 5 and 12.
- See, eg, Certain Activities Carried Out by Nicaragua in the Border Area (Costa Rica v Nicaragua) and Construction of a Road in Costa Rica along the San Juan River (Nicaragua v Costa Rica) (Judgment)  ICJ Rep 665, 704–05, paras 97–99 (holding that the presence of Nicaragua’s military personnel in the territory under Costa Rica’s sovereignty amounted to a violation of Costa Rica’s territorial sovereignty); see also Tallinn Manual 2.0, commentary to rule 4, para 6.
- Tallinn Manual 2.0, commentary to rule 4, para 7; commentary to rule 32, para 9.
- Tallinn Manual 2.0, commentary to rule 4, para 11.
- Tallinn Manual 2.0, commentary to rule 4, para 12.
- Tallinn Manual 2.0, commentary to rule 4, para 13.
- Tallinn Manual 2.0, commentary to rule 4, para 14.
- Tallinn Manual 2.0, commentary to rule 4, para 15.
- Tallinn Manual 2.0, commentary to rule 4, para 16.
- Tallinn Manual 2.0, commentary to rule 4, para 18.
- Dutch Ministry of Foreign Affairs, Letter to the parliament on the international legal order in cyberspace, Letter of 5 July 2019 from the Minister of Foreign Affairs to the President of the House of Representatives on the international legal order in cyberspace, p. 3.
- French Ministry of the Armies, International Law Applied to Operations in Cyberspace, p. 6.
- In favour: see, eg, Theodore Christakis, ‘The ICJ Advisory Opinion on Kosovo: Has International Law Something to Say about Secession?’ (2011) 24 LJIL 73, 84; Marcelo Kohen, ‘The Court’s Contribution to Determining the Content of Fundamental Principles of International Law’ in Giorgio Gaja and Jenny Grote Stoutenburg (eds), Enhancing the Rule of Law through the International Court of Justice (Brill 2012) 145. Against: see, eg, Tallinn Manual 2.0, commentary to rule 4, para 3.
- Corfu Channel Case (UK v Albania) (Merits)  ICJ Rep 4, 22.
- UN GA Res 55/63 (4 December 2000), Doc A/RES/55/63, para 1(a).
- Cf. UN GGE 2015 report, paras 13(c) and 28(e) (using non-mandatory language to express the due diligence principle in the cyber context: “States should not knowingly allow their territory to be used for internationally wrongful acts using [cyber means]” and “States ... should seek to ensure that their territory is not used by non-State actors to commit such acts”, respectively) (emphases added).
- See Luke Chircop, ‘A Due Diligence Standard of Attribution in Cyberspace’ (2018) 67 ICLQ 643.
- See also Tallinn Manual 2.0, commentary to rule 6, para 4 (unanimously endorsing this view).
- Australia, ‘Australia’s International Cyber Engagement Strategy - Annex A: Australia’s Position on How International Law Applies to State Conduct in Cyberspace’ (October 2017) 91, stating that “if a state is aware of an internationally wrongful act originating from or routed through its territory, and it has the ability to put an end to the harmful activity, that state should take reasonable steps to do so consistent with international law”.
- Czech Republic, Comments submitted by the Czech Republic in reaction to the initial “pre-draft” report of the Open-Ended Working Group on developments in the field of information and telecommunications in the context of international security (undated), stating that “ICT-specific norms reflect a general principle of international law obliging States to ensure that territory and objects over which they enjoy sovereignty are not used to harm other States’ rights.”
- Estonia, ‘President of the Republic at the opening of CyCon 2019’ (29 May 2019), stating that “states have to make reasonable efforts to ensure that their territory is not used to adversely affect the rights of other states.”
- Finland, ‘Statement by Ambassador Janne Taalas at the second session of the open-ended Working Group (OEWG) on developments in the field of information and telecommunications in the context of international security’ (11 February 2020), stating that “States have an obligation not to knowingly allow their territory to be used for activities that cause serious harm to other States, whether using ICTs or otherwise.”
- French Ministry of the Armies, ‘International Law Applied to Operations in Cyberspace’ (9 September 2019) 6, stating that “In compliance with the due diligence requirement, [France] ensures that its territory is not used for internationally wrongful acts using ICTs. This is a customary obligation for States, which must (i) use cyberspace in compliance with international law, and in particular not use proxies to commit acts which, using ICTs, infringe the rights of other States, and (ii) ensure that their territory is not used for such purposes, including by non-state actors.”
- Dutch Ministry of Foreign Affairs, ‘Letter to the parliament on the international legal order in cyberspace’ (5 July 2019), stating that ‘The Netherlands ... does regard the principle [of due diligence] as an obligation in its own right, the violation of which may constitute an internationally wrongful act.’
- Tallinn Manual 2.0, commentary to rule 6, para 5.
- Cf. Case Concerning Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Bosnia and Herzegovina v Serbia and Montenegro) (Judgement)  ICJ Rep 43, para 430; see further James Crawford, State Responsibility: The General Part (CUP 2013) 226–32 (on the distinction between due diligence and obligations of prevention); Rudiger Wolfrum, ‘Obligation of Result Versus Obligation of Conduct: Some Thoughts About the Implementation of International Obligations’ in Mahnoush H Arsanjani et al, Looking to the Future: Essays on International Law in Honor of Michael Reisman (Brill 2010).
- Corfu Channel judgment, para 22; Tallinn Manual 2.0, commentary to rule 6, para 2 and 15.
- Tallinn Manual 2.0, rule 6.
- Tallinn Manual 2.0, commentary to rule 6, para 18-24.
- Tallinn Manual 2.0, rule 6.
- Tallinn Manual 2.0, commentary to rule 6, para 37-42.
- Tallinn Manual 2.0, commentary to rule 6, para 43; commentary to rule 7, para 2 and 18.
- Tallinn Manual 2.0, commentary to rule 6, para 7.
- Tallinn Manual 2.0, commentary to rule 6, para 21.
- Tallinn Manual 2.0, commentary to rule 6, para 28.
- Tallinn Manual 2.0, commentary to rule 6, para 38-42.
- Tallinn Manual 2.0, commentary to rule 6, para 39.
- ILC Articles on State Responsibility, Commentary, part 3 ch 2 at para 1.
- Austria, Pre-Draft Report of the OEWG - ICT: Comments by Austria (31 March 2020), stating that ‘a violation of the principle of State sovereignty constitutes an internationally wrongful act – if attributable to a State – for which a target State may seek reparation under the law of State responsibility. A target State may also react through proportionate countermeasures.’ (emphasis added).
- Estonia, ‘President of the Republic at the opening of CyCon 2019’ (29 May 2019), stating that “states have the right to react to malicious cyber operations, including using diplomatic response but also countermeasures”
- French Ministry of the Armies, ‘International Law Applied to Operations in Cyberspace’ (9 September 2019) 6, stating that ‘In response to a cyberattack, France may consider diplomatic responses to certain incidents, countermeasures, or even coercive action by the armed forces if an attack constitutes armed aggression.’
- Germany, ‘Statement by Ambassador Dr Thomas Fitschen, Director for the United Nations, Cyber Foreign Policy and Counter-Terrorism, Federal Foreign Office of Germany’ (November 2018) 3, stating that ‘in case of a cyber operation that is in breach of an international legal obligation below the level of the use or threat of force prohibited by Art. 2 (IV) [of the UN Charter] States are also entitled to take countermeasures as allowed by international law.’
- Japan, ‘Japan’s Position Paper for the Report of the United Nations Open-Ended Working Group on “Developments in the Field of Information and Telecommunications in the Context of International Security”’ (undated), stating that ‘Japan recognizes that basic rules on State responsibility including those on countermeasures applies to cyberspace.’
- Dutch Ministry of Foreign Affairs, ‘Letter to the parliament on the international legal order in cyberspace’ (5 July 2019) 7.
- United Kingdom, ‘Statement on Other Disarmament Measures and International Security to the 72nd UNGA First Committee’ (23 October 2017), stating that ‘We reaffirm that the law of state responsibility applies to cyber operations in peacetime, including the availability of the doctrine of countermeasures in response to internationally wrongful acts.’
- Brian J. Egan, ‘Remarks on International Law and Stability in Cyberspace’ (10 November 2016), stating that countermeasures are available ‘to address malicious cyber activity’ if that activity amounts to a prior internationally wrongful act attributable to another State.
- Brazil, ‘Open-ended Working Group on developments in the field of information and telecommunications in the context of international security: Second Substantive Session - New York, 11 February 2020: Statement by the Delegation of Brazil’ (11 February 2020), stating that ‘In the case of malicious acts in cyberspace, it is often difficult to attribute responsibility to a particular State or actor with unqualified certainty. A decision to resort to countermeasures in response to such acts carries a high risk of targeting innocent actors, and of triggering escalation.’
- China, ‘Statement by the Chinese Delegation at the Thematic Debate of the First Committee of the 72th UNGA’ (October 2017), stating that ‘Countries should discuss application of international law in the manner conducive to maintain peace, avoid introducing force, deterrence and countermeasures into cyberspace, so as to prevent arms race in cyberspace and reduce risks of confrontation and conflicts.’
- Cuba, ‘Declaration by Miguel Rodríguez, Representative of Cuba, at the Final Session of Group of Governmental Experts on Developments in the Field of Information and Telecommunications in the Context of International Security’ (23 June 2017), registering ‘serious concern over the pretension of some, reflected in paragraph 34 of the draft final report, to convert cyberspace into a theater of military operations and to legitimize, in that context, unilateral punitive force actions, including the application of sanctions and even military action by States claiming to be victims of illicit uses of ICTs.’ (emphasis added).
- ILC Articles on State Responsibility, Art 49(1); Case Concerning the Gabčíkovo-Nagymaros Project (Hungary/Slovakia) (Judgment)  ICJ Rep 7, para 83.
- ILC Articles on State Responsibility, Art 52(3) – 52(4).
- ILC Articles on State Responsibility, Art 52(1)(a). According to the UK Attorney General, the UK does not feel legally obliged, when taking countermeasures in response to a covert cyber intrusion, to “give prior notification to the hostile state”. UK Attorney General, Jeremy Wright QC MP, ‘Cyber and International Law in the 21st Century’.
- ILC Articles on State Responsibility, Art 28-41; the list of consequences includes (i) continued duty of performance, (ii) cessation and non-repetition, (iii) reparation, and (iv) particular consequences of a serious breach of obligations under peremptory norms of general international law.
- ILC Articles on State Responsibility, Art 52(1)(b) – 52(2).
- ILC Articles on State Responsibility, Art 49(1); Case Concerning the Gabčíkovo-Nagymaros Project (Hungary/Slovakia) (Judgment)  ICJ Rep 7, para 87. The list of consequences in Art 28-41 includes (i) continued duty of performance, (ii) cessation and non-repetition, (iii) reparation, and (iv) particular consequences of a serious breach of obligations under peremptory norms of general international law.
- ILC Articles on State Responsibility, Art 49(3).
- Such as the obligation to refrain from the threat or use of force as embodied in the UN Charter, obligations for the protection of fundamental human rights, and obligations of a humanitarian character prohibiting reprisals. ILC Articles on State Responsibility, Art 50(1).
- ILC Articles on State Responsibility, Art 50(2).
- Articles on State Responsibility, Art 51; Case Concerning the Gabčíkovo-Nagymaros Project (Hungary/Slovakia) (Judgment)  ICJ Rep 7, para 85.
- ILC Articles on State Responsibility, Art 54.
- President of Estonia, Kersti Kaljulaid, ‘President of the Republic at the opening of CyCon 2019’ (29.05.2019).
- Michael N Schmitt, ‘Estonia Speaks Out on Key Rules for Cyberspace’ Just Security (10.06.2019), considering the Estonian interpretation to be “an advantageous development in the catalogue of response options that international law provides to deal with unlawful acts”.
- French Ministry of the Armies, International Law Applied to Operations in Cyberspace, p. 10, arguing that collective countermeasures are not authorised under international law.
- Jeff Kosseff, ‘Collective Countermeasures in Cyberspace,’ (2020) Notre Dame Journal of International & Comparative Law Vol. 10, Iss. 1, 34; François Delerue, Cyber Operations and International Law (CUP 2020), 457.
- ILC Articles on State Responsibility, Commentary in Part 3, Chapter 2 on Art 49, para 3.
- ILC Articles on State Responsibility, Commentary to Part One, Chapter 5, para 8 (noting that “[i]n a bilateral dispute over State responsibility, the onus of establishing responsibility lies in principle on the claimant State”).
- See, eg, Trail Smelter case (United States v Canada) (Award) (1941) 3 RIAA 1905, 1965; see also Robin Geiss and Henning Lahmann, ‘Freedom and Security in Cyberspace: Shifting the Focus Away from Military Responses Towards Non-Forcible Countermeasures and Collective Threat-Prevention’ in Katharina Ziolkowski (ed), Peacetime Regime for State Activities in Cyberspace (NATO CCD COE 2013) 624 (noting that in cases where State responsibility is involved, the required threshold tends to shift towards ‘clear and convincing’”).
- James Green, ‘Fluctuating Evidentiary Standards for Self-Defence in the International Court of Justice’ (2009) 58 ICLQ 163, 167 (emphasis original).
- ILC Articles on State Responsibility, Commentary in Part 3, Chapter 2 on Art 49, para 3.
- ILC Articles on State Responsibility, Art 25(1)(a).
- ILC Articles on State Responsibility, Art 25(1)(b).
- ILC Articles on State Responsibility, Art 25(1)(b).
- ILC Articles on State Responsibility, Art 25(1)(b).
- Tallinn Manual 2.0, commentary to rule 26, para 2.
- Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits)  ICJ Rep 14, para 95.
- US Department of Defense, Office of the General Counsel, Law of War Manual (June 2015), paras. 188.8.131.52, 184.108.40.206.
- Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits)  ICJ Rep 14, para 191.
- Tallinn Manual 2.0, commentary to rule 71, para 8.
- E Zoller, Peacetime Unilateral Remedies: An Analysis of Countermeasures (Transnational 1984) 5.
- Articles on State Responsibility, commentary to Part Three, Chapter II, para. 3.
- Jeff Kosseff, ‘Retorsion as a Response to Ongoing Cyber Operations’ in Taťána Jančárková et al (eds), 20/20 Vision: The Next Decade (CCD COE 2020) 17–22.
4.3 Bibliography and further reading
- William Banks, State Responsibility and Attribution of Cyber Intrusions After Tallinn 2.0, 95 Tex. L. Rev. 1487 (2017)
- Luke Chircop, ‘A Due Diligence Standard of Attribution in Cyberspace’ (2018) 67 ICLQ.
- James Crawford, State Responsibility: The General Part (CUP 2013).
- Dan Efrony and Yuval Shany, 'A Rule Book on the Shelf? Tallinn Manual 2.0 on Cyberoperations and Subsequent State Practice' (2018) 112 AJIL.
- Robin Geiss and Henning Lahmann, ‘Freedom and Security in Cyberspace: Shifting the Focus Away from Military Responses Towards Non-Forcible Countermeasures and Collective Threat-Prevention’ in Katharina Ziolkowski (ed), Peacetime Regime for State Activities in Cyberspace (NATO CCD COE 2013).
- ET Jensen and S Watts, ‘A Cyber Duty of Due Diligence: Gentle Civilizer or Crude Destabilizer’ (2017) 95 Tex. L. Rev. 1555
- Christian Payne & Lorraine Finlay, Addressing Obstacles to Cyber-Attribution, 49 Geo. Wash. Int’l L. Rev. 535 (2017).
- Marco Roscini, Cyber Operations and the Use of Force in International Law (OUP 2014).
- Michael N. Schmitt, ‘“Below the Threshold” Cyber Operations: The Countermeasures Response Option and International Law’, 54 Va. J. Int’l L. 697 (2014).
- Michael N Schmitt (ed), Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations (CUP 2017).
- US Department of Defense, Office of the General Counsel, Law of War Manual (June 2015)
- Scenario by: Kenneth Kraszewski
- Analysis by: Kenneth Kraszewski
- Reviewed by: Anna-Maria Osula, Peter Stockburger, David Wallace
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