Scenario 05: State investigates and responds to cyber operations against private actors in its territory
This scenario considers a series of malicious cyber operations originating from one State’s territory and targeted against private entities on the territory of another State. In the course of investigation, the victim State opts to penetrate the networks of its adversary without its consent and discovers that the latter’s military personnel was indeed involved in some of the operations. The scenario analyses the degrees of responsibility of the State of origin, the rules it may have breached, and the ability of the victim State to justify its response under the law of countermeasures.
DDoS, data deletion, attribution, non-State actors, evidence, sovereignty, due diligence, countermeasures
Important commercial entities and financial institutions in State A fall victim to a massive distributed denial of service (DDoS) type of campaign for several days, resulting in down-time costs that amount to millions of EUR (incident 1).
Later, it is found that some of the computers were infected by malware and that the data, including operating system data, had been damaged or deleted, rendering the computers inoperative (incident 2). Most of the targeted entities have been able to recover the data from back-ups and restore the functionality of the computers, albeit at a substantial cost.
The attack has been claimed by a group called “State B Digital Army” that has been active on the Internet for some time and is openly critical of foreign policy of State A. The group bears a name clearly referring to State B, which has in the past been allegedly involved in State-run cyber espionage operations against State A. State B as such has however never admitted any relation to the group.
The technical aspects of the first incident, or rather its lack of sophistication, seem to suggest that the attackers were just an amateur group. By contrast, the scale of the attack indicates that a State actor could have been involved in some capacity. Also, most of the group’s activities seem to originate from the territory of State B, although the persons involved and their exact location are unknown to State A.
Considering that States A and B have not had mutual diplomatic relations for many years, that State B is uncooperative in mutual legal assistance requests, and that there is a risk of destruction of evidence by State B, State A decides to remotely access several computers in the territory of State B without State B’s consent, in the course of a criminal investigation by State A’s cyber police unit (incident 3).
During the cyber operation against State B, State A discovers that a minority of the attacks indeed originated from the network of State B’s General Staff (incident 4). State A is also able to identify some of the individuals responsible for the attacks and consequently issues arrest warrants for these individuals, two of whom happen to be military personnel of State B working in cyber intelligence (incident 5).
State B denies all allegations, stating that these individuals were acting on their own, outside their working hours, and it decries the “violation of its sovereignty” by State A.
Similar real-world incidents
For a general overview of the structure of analysis in this section, see Note on the structure of articles.
Attribution to State B
|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).
The fact that the operation against State A was partly launched from the governmental cyber infrastructure of State B, as found out in incident 4, is insufficient for the purposes of attribution of the operation to State B. However, it indicates that State B may have been associated with the operation in question. Nevertheless, as soon as the two officers are identified in incident 5, the situation changes: even though they might have been acting on their own (as State B claimed in the aftermath of the incidents), their conduct would still be attributable to State B. This is because the mere fact that a State organ was acting ultra vires, i.e., in excess of authority or in contravention of instructions, does not remove attribution to the relevant State. It is not necessary to prove that they were getting orders from their superiors, even though such information might be helpful for the purposes of criminal investigation conducted by State A authorities.
The information available to State A after incident 5 supports only an attribution of the conduct of the military personnel of State B to that State. By contrast, there does not seem to be sufficient evidence to link State B to any of the activities of the so-called “State B Digital Army” and its supporters. That being said, there are several options under the law of State responsibility on the basis of which such conduct might in fact be attributable to State B:
Options 2–4 are manifestly inapplicable to the facts of the scenario given that there is no indication that the so-called State B Digital Army was exercising any form of governmental authority or attempting to form a State of its own. Option 5 (acknowledgment and adoption) also does not apply to the present facts because State B vehemently denied any association with the cyber operations against State A.
The only remaining mode of attribution is that under option 1, which reflects Article 8 of the ILC’s Draft Articles on State Responsibility (i.e., the existence of instructions, direction, or control). In this regard, the mere fact that State B and the “State B Digital Army” may have shared political goals and aims does not suffice for the purposes of attribution of the latter’s conduct to the former. Similarly, the mere fact that some of the activities were conducted from both government and private cyber infrastructure in State B is not sufficient. What would need to be established is some form of subordination between the non-State actor and the potentially responsible State. As the scenario does not offer any indication of such subordination, it can be concluded that the available facts do not support the attributability of the conduct of State B Digital Army to State B.
| The law of State responsibility as such does not contain generally applicable burdens, standards, or methods of proof, and these matters are instead ordinarily determined by the relevant forum.
However, in case a State is considering a response to an internationally wrongful act, the standard of attribution is that of "reasonableness", i.e. "States must act as reasonable States would in the same or similar circumstances when considering responses to them." This depends, among other factors, on the "reliability, quantum, directness, nature (e.g., technical data, human intelligence), and specificity of the relevant available information when considered in light of the attendant circumstances and the importance of the right involved." Nevertheless, there is no obligation to publicly provide the evidence.
Specific rules may apply to some responses, so when State A responds with countermeasures after misattributing an internationally wrongful act to State B, it commits an internationally wrongful act of its own, even though it correctly applied the "reasonableness" standard of attribution.
In incidents 1 and 2, State A does not have much information to ascertain who was responsible for the cyberattacks. Its decision to gather more evidence by launching a criminal investigation and accessing State B’s networks without asking for permission (incident 3) might be viewed as reasonable with regard to the circumstances (suspected involvement of State B), if there is no better way to obtain more evidence. This can qualify as a countermeasure of State A against State B (see below). However, State A must be aware that it might be committing an internationally wrongful act if State B is not responsible for incidents 1-2, even if the hack-back seemed reasonable in the circumstances.
There is no obligation to publicly provide evidence upon which State A attributes the cyber operation to State B.
Breach of an international obligation by State B
Sovereignty of State A
|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,|
[s]overeignty in the relations between States signifies independence. Independence in regard to a portion of the globe is the right to exercise therein, to the exclusion of any other State, the functions of a State.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 several States including Germany and 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.
Publicly available national positions that address this issue include: (2020), (2021), (2022), (2021), (2020), (2019), (2021), (2020), (2019), (2021), (2020), (2020), (2021), (2021), (2021), (2019), (2020), (2021), (2021), (2021), (2022), (2021), (2018), (2021), (2022), (2012), (2016), (2020), (2021).
The DDoS attacks (incident 1) probably did not amount to a violation of State A’s sovereignty. There were no physical consequences, even though some individuals and entities in State A could be ‘physically’ affected by being unable to pay for goods and services, and there were significant economic losses as a result of the attacks. The loss of functionality was only temporary.
Inherently governmental functions were probably not affected by incident 1 – the inability to pay invoices might have some effect on the functioning of some government organizations in State A, but the causation is probably not proximate enough given the short timeframe of the incident (several days). The organizations can postpone the payments due to unforeseeable and irresistible circumstances, which likely mitigates any adverse effects on their functions.
However, the deletion of data (incident 2), leading to a loss of functionality, could qualify as a violation of State A’s sovereignty (option 3 above). This is regardless of the fact that the affected infrastructure was non-governmental.
Prohibited intervention by State B
|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:|
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.In order for an act, including a cyber operation, to qualify as a prohibited intervention, it must fulfil the following conditions:
Publicly available national positions that address this issue include: (2020), (2021), (2022) (2021), (2019), (2021), (2020), (2020), (2021), (2021), (2019), (2020), (2021), (2021), (2021), (2022), (2021), (2018), (2021), (2022), (2016), (2020), (2021).
It would be difficult to argue that State B was involved in a prohibited intervention in State A’s internal affairs. To begin with, it is uncertain whether State A’s domaine réservé — in itself an imprecise category under international law — was affected by incidents 1-2. The cyber activities were targeting State A’s financial sector, which is traditionally perceived as private, even if State A had a share in its ownership. Perhaps if the operations had been directed at State A’s central bank or at the integrity of financial data upon which State A’s pension or welfare system relied, this would support the qualification of the operation as an intrusion into the domaine réservé.
Even assuming that the first prong of the test was met by the cyber operations in question, there is no evidence that any of the incidents were coercive in nature as against State A. In other words, the available facts do not support any attempt to compel State A to take any action it would otherwise not take. As such, the cyber operations in the scenario do not seem to qualify as a prohibited intervention under international law.
Due diligence obligation of State B
| 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.
Publicly available national positions that address this issue include: (2020), (2022), (2020), (2019), (2021), (2019), (2021), (2020), (2021), (2021), (2019), (2020), (2021), (2021), (2021), (2022), (2021), (2021), (2021).
The due diligence analysis is important in the situation when State A does not have enough evidence to attribute incidents 1-2 to State B directly. If State B is in breach of its obligation of due diligence, State A might still have the option of justifying its responsive operation (incident 3) as a countermeasure.
Following from the above analysis of sovereignty, incident 2 (the deletion of data leading to a loss of functionality) is contrary to the rights of State A, and would have been unlawful if conducted by State B. It would be more difficult to similarly qualify incident 1 (the DDoS attack).
The cyber activities leading to incident 2 were conducted from the cyber infrastructure in the territory of State B; however, State B’s due diligence obligation is not breached solely by the fact that these incidents happened, even though they resulted in serious adverse consequences and were contrary to the rights of State A. State A would have to prove that State B had an actual or constructive knowledge of the harmful cyber activities at the time they were launched, and that it neglected its duty to terminate them.
The information that some of the harmful cyber activities were launched from State B’s government infrastructure is available to State A from incident 4 onwards. Even if it cannot be proved that State B actually gave orders to its organs, or instructed or directed the non-State actors (“State B Digital Army”) to conduct the DDoS attacks and data deletion (see the section on attribution above), the constructive knowledge requirement (“should have known”) triggers the breach of its due diligence obligation for the activities originating from its government cyber infrastructure. State B could argue that its government infrastructure was taken over by non-State actors or a third State, or that it did what was to be expected from a reasonable State to terminate the activities, but the burden of proof would then shift to its side.
State B therefore violated its obligation of due diligence with respect to those harmful cyber activities in the scenario that could not be directly attributed to it. With respect to the conduct that is attributable to State B, that State bears direct responsibility, which supersedes any violation of due diligence.
Sovereignty of State B: extraterritorial jurisdiction by State A in State B
(See above for the discussion of sovereignty. This analysis is based on the presumption that sovereignty is a primary rule of international law.)
As State A decides to remotely access several computers in State B’s territory in search of evidence (incident 3), it is exercising its enforcement jurisdiction in State B’s territory. Absent State B’s consent or other justification, State A’s action is in violation of State B’s sovereignty.
State A might try to justify its actions by invoking countermeasures.
Countermeasures by 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 and 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.
Publicly available national positions that address this issue include: (2020), (2021), (2022), (2019), (2021), (2020), (2019), (2021), (2020), (2021), (2021), (2019), (2020), (2021), (2021), (2021), (2022), (2021), (2018), (2021), (2022), (2016), (2020), (2021).
An interesting question arises at this point: is State A engaging in countermeasures against State B by exercising its enforcement jurisdiction in State B’s territory? (Let us suppose that it would be a violation of State A’s obligation to respect State B’s sovereignty, unless it is State A’s lawful countermeasure.)
We know that State B’s activities in incident 2 and attributed in incidents 4-5 may amount to a violation of State A’s sovereignty, and hence an internationally wrongful act by State B; accordingly, State A would be entitled to respond with countermeasures (supposing that the effects of State B’s activities were still ongoing – for instance, if some of the deleted data could not be restored). Also, let us suppose that State A did not have the obligation to call upon State B for cessation, non-repetition, and reparation, and that it did not have the obligation to notify State B of the impending countermeasure, because that would likely defeat its purpose. The envisaged countermeasure is likely commensurate with the injury suffered. As for the purpose of the countermeasure, it serves to induce State B to comply with its obligations, because it aims to establish a firm attribution of its internationally wrongful act.
However, State A does not have the information about the attribution yet. Is State A engaging in countermeasures, if State B’s internationally wrongful act has not been established?
Ex post facto, it seems that the countermeasures were lawful, because State B had committed an internationally wrongful act; ex ante, however, State A could not have known that. Intuitively, it may seem that State A paradoxically committed an internationally wrongful act in response to an internationally wrongful act of State B.
However, the standard for the taking of countermeasures is an objective one. The law of State responsibility does not require a subjective element to establish the wrongfulness of an act, nor does it deal with factually impossible attempts of internationally wrongful acts.
According to the commentary to the Articles on State Responsibility, “[a] State which resorts to countermeasures based on its unilateral assessment of the situation does so at its own risk and may incur responsibility for its own wrongful conduct in the event of an incorrect assessment.” Therefore, State A’s countermeasures were lawful: they were done in reaction to an objectively internationally wrongful act of State B.
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.
- Tallinn Manual 2.0, commentary to rule 15, para. 13.
- Tallinn Manual 2.0, commentary to rule 15, para. 13.
- ILC, Articles on State Responsibility, Art. 7.
- 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.
- K Mačák, ‘Decoding Article 8 of the International Law Commission’s Articles on State Responsibility: Attribution of Cyber Operations by Non-State Actors’ (2016) 21 JCSL 405, 415 (“the fact of a goal shared by the State and the private actor is insufficient without further evidence establishing the subordination between the two”).
- Tallinn Manual 2.0, commentary to rule 15, para. 13-14.
- K Mačák, ‘Decoding Article 8 of the International Law Commission’s Articles on State Responsibility: Attribution of Cyber Operations by Non-State Actors’ (2016) 21 JCSL 405, 426–27 (noting that all three standards under Article 8 share the need for “a subordinate relationship between the State and the private actor”) (emphasis removed).
- See further Marco Roscini, ‘Evidentiary Issues in International Disputes Related to State Responsibility for Cyber Operations’ (2015) 50 Texas International Law Journal 233; Isabella Brunner, Marija Dobrić and Verena Pirker, ‘Proving a State’s Involvement in a Cyber-Attack: Evidentiary Standards Before the ICJ’ (2015) 25 Finnish Yearbook of International Law 75; Tomohiro Mikanagi and Kubo Mačák, ‘Attribution of Cyber Operations: An International Law Perspective on the Park Jin Hyok case’ (2020) 9 Cambridge International Law Journal 51, 64-68.
- ILC Articles on State Responsibility, commentary to chapter III, para 4 ("Questions of evidence and proof of such a breach fall entirely outside the scope of the articles."); ibid, commentary to Art 19, para 8 ("Just as the articles do not deal with questions of the jurisdiction of courts or tribunals, so they do not deal with issues of evidence or the burden of proof.").
- Tallinn Manual 2.0, Chapter 4 Section 1, para 8.
- Tallinn Manual 2.0, Chapter 4 Section 1, para 10; Cf. Yeager v Islamic Republic of Iran (1987) 17 Iran-US CTR 92, 101–02 (‘[I]n order to attribute an act to the State, it is necessary to identify with reasonable certainty the actors and their association with the State.’).
- Tallinn Manual 2.0, Chapter 4 Section 1, para 10.
- According to the UK Attorney General, "[t]here 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." (UK Attorney General, Jeremy Wright QC MP, 'Cyber and International Law in the 21st Century'; see also Tallinn Manual 2.0, Chapter 4 Section 1 chapeau, para 13.
- Tallinn Manual 2.0, Chapter 4 Section 1, para 12; see also ILC Articles on State Responsibility, Art 49 para 3 (“A State taking countermeasures acts at its peril, if its view of the question of wrongfulness turns out not to be well founded.”)
- Tallinn Manual 2.0, Chapter 4 Section 1 chapeau, paragraph 13.
- 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’).
- 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.’
- Finland, ‘International law and cyberspace: Finland’s national positions’ (15 October 2020), 3, stating that ‘Finland sees sovereignty as a primary rule of international law, a breach of which amounts to an internationally wrongful act and triggers State responsibility. This rule is fully applicable in cyberspace.’
- 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’.
- Germany, ‘On the Application of International Law in Cyberspace: Position Paper’ (March 2021), p. 3, noting that ‘Germany agrees with the view that cyber operations attributable to States which violate the sovereignty of another State are contrary to 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.
- Germany, ‘On the Application of International Law in Cyberspace: Position Paper’ (March 2021), p. 4.
- Dutch Ministry of Foreign Affairs, ‘Letter to the parliament on the international legal order in cyberspace’ (5 July 2019), 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.
- But see Tallinn Manual 2.0, commentary to rule 4, para. 14 (noting that some of the experts considered that “a temporary, but significant, loss of functionality, as in the case of a major DDoS operation” would qualify as a violation of the victim State’s sovereignty).
- Tallinn Manual 2.0, commentary to rule 4, para. 13.
- Tallinn Manual 2.0, commentary to rule 2, para. 3.
- 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; Finland, ‘International law and cyberspace: Finland’s national positions’ (15 October 2020), 3; Germany, ‘On the Application of International Law in Cyberspace: Position Paper’ (March 2021), 5.
- 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”).
- See also Harriet Moynihan, ‘The Vital Role of International Law in the Framework for Responsible State Behaviour in Cyberspace’ (2020) 5 Journal of Cyber Policy __, ___ [10–12 in pre-print].
- See, eg, 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, defining coercion as ‘compelling a state to take a course of action (whether an act or an omission) that it would not otherwise voluntarily pursue’ and noting that ‘[t]he goal of the intervention must be to effect change in the behaviour of the target state’; Germany, ‘On the Application of International Law in Cyberspace: Position Paper’ (March 2021), 5, defining coercion as a situation in which a State’s ‘will is manifestly bent by the foreign State’s conduct’ and noting that ‘the acting State must intend to intervene in the internal affairs of the target State’; see also Tallinn Manual 2.0, commentary to rule 66, para 19 (‘The majority of Experts was of the view that the coercive effort must be designed to influence outcomes in, or conduct with respect to, a matter reserved to a target State.’).
- 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.
- See, eg, Australia, ‘Supplement to Australia’s Position on the Application of International Law to State Conduct in Cyberspace’ (2019) 4 (‘A prohibited intervention is one that interferes by coercive means (in the sense that they effectively deprive another state of the ability to control, decide upon or govern matters of an inherently sovereign nature), either directly or indirectly, in matters that a state is permitted by the principle of state sovereignty to decide freely.’); New Zealand, ‘The Application of International Law to State Activity in Cyberspace’ (1 December 2020), para 9(b) (stating that a State cyber activity is coercive if ‘there is an intention to deprive the target state of control over matters falling within the scope of its inherently sovereign functions’); see also Tallinn Manual 2.0, commentary to rule 66, para 19 (‘A few Experts took the position that to be coercive it is enough that an act has the effect of depriving the State of control over the matter in question.’).
- Harriet Moynihan, ‘The Vital Role of International Law in the Framework for Responsible State Behaviour in Cyberspace’ (2020) 5 Journal of Cyber Policy __, ___ [11 in pre-print].
- Tallinn Manual 2.0, commentary to rule 66, para 21.
- Tallinn Manual 2.0, commentary to rule 66, paras 19 and 27.
- Tallinn Manual 2.0, commentary to rule 66, para 24 (the exact nature of the causal nexus was not agreed on).
- Cf. Maurer and Schmitt, ‘Protecting Financial Data in Cyberspace: Precedent for Further Progress on Cyber Norms?’ (2017) (“In the context of financial data, an operation targeting the integrity of financial data upon which the State pension or welfare system relied in order to compel the target State to adopt a particular domestic policy would exemplify prohibited cyber intervention.”).
- Cf. Tallinn Manual 2.0, commentary to rule 66, para. 21 (“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).”).
- 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. 40.
- Cf. J Kulesza, Due Diligence in International Law (Brill Nijhoff 2016) 53.
- Tallinn Manual 2.0, commentary to rule 4, para. 18, and to rule 11, para. 7.
- 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 para 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 para 1; Case Concerning the Gabčíkovo-Nagymaros Project (Hungary/Slovakia) (Judgment) 1997 ICJ Rep 7, para 83.
- ILC Articles on State Responsibility, Art 52 paras 3 - 4.
- ILC Articles on State Responsibility, Art 52 para 1 subpara 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 para 1 subpara b) – Art 52 para 2.
- ILC Articles on State Responsibility, Art 49(1); Case Concerning the Gabčíkovo-Nagymaros Project (Hungary/Slovakia) (Judgment) 1997 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) 1997 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.
- Tallinn Manual 2.0, commentary to rule 4, para. 18, and to rule 11, para. 7.
- Articles on State Responsibility, paragraph 3 of the commentary to Art. 49.
Bibliography and further reading