It remains unsettled whether states indirectly injured by breaches of collective or community obligations have the right to take ‘general interest’ countermeasures in response to such breaches. While third states do not have a separate right to take countermeasures in support of the injured state, within certain limits, they may assist the injured state in taking its own countermeasures.
Background
A significant point of contention, both generally and in cyberspace, is the question of whether states other than the injured state may resort to countermeasures under customary international law. These have been referred to interchangeably as ‘collective’ or ‘third-party’ countermeasures.
Take the example of a state whose elections, healthcare services or other critical infrastructure are being targeted by cyber operations attributable to another state. Or a state that is being attacked or invaded by conventional means, such as Ukraine. The question is: to what extent may a state that has not been directly injured by the breach come to the victim state’s aid by using cyber or non-cyber measures that are in principle unlawful to make the responsible state stop and/or repair the harm? As noted by Ireland in its national position on international law in cyberspace:
Further, if there is no injured state as such, but the responsible state is committing grave human rights violations or international crimes such as genocide against its own population, may other states take countermeasures to make the responsible state stop and/or repair the wrong?
As will be discussed throughout this chapter, some states have expressed support for those types of measures both in the cyber context and more generally. One reason might be that international law has few collective enforcement mechanisms. The right to collective self-defence only allows third states to take forcible action in response to an armed attack against another state. If states other than the injured state are not permitted to take countermeasures in support of the injured state, non-forcible options to bring the responsible state into compliance with international law would be limited.
Other states have cautioned against the risks of states other than the injured state taking measures that would, in principle, breach international law. These include conflict escalation and the possibility of undermining the role of the UN collective security system, especially the Security Council’s mandate to take collective action to maintain or restore international peace and security. For instance, Israel has in the past argued that the taking of countermeasures by ‘interested’ (as opposed to injured) states ‘would have a destabilizing effect by creating a parallel mechanism for responding to serious breaches which lacked the coordinated, balanced and collective features of existing mechanisms’. Similarly, the UK noted that these measures could be ‘potentially highly destabilizing of treaty relations’.
So far as the law is concerned, the ICJ has once examined the legality of countermeasures taken by states other than the injured state in the Nicaragua case. The question facing the court was whether measures taken by the US against Nicaragua allegedly in support of three states were lawful. For the most part, the US measures were found to be threats or use of force, but they also included non-forcible measures that violated the principle of non-intervention, such as the supply of intelligence, as well as logistical and financial support to rebels. The court stated:
It has been suggested that this passage stands for the proposition that countermeasures by states other than the injured state are not allowed under international law. While the use of force can never be justified as a countermeasure, it is not entirely clear what the ICJ was suggesting with respect to the non-forcible measures taken by the US. In particular, it is also possible that the court was not rejecting the permissibility of countermeasures by states other than the injured state in general, but only in that particular case because the relevant pre-conditions may not have been met by the US.
As noted in Chapter 1, the ILC Articles adopted in 2001 expressly recognize the right of injured states to take lawful countermeasures. But they are silent as to whether states other than the injured state may take those measures. Specifically, Article 49(1) of the Articles speaks only of the ‘injured State’ when recognizing a state’s right to resort to countermeasures against a state responsible for an internationally wrongful act. An ‘injured State’ is: a) a state to which the obligation breached is owed individually, or, if the obligation is owed to a group of states or the international community as a whole, b) a state that is ‘specially affected’ by the breach, or c) a group of states whose position has been radically changed by the breach. This is a narrow group of states. Even in the case of erga omnes or erga omnes partes obligations, a state will only be considered ‘injured’ if it is affected by the breach in a particular way, that is, in a way that distinguishes this state from the generality of other states to which the obligation is owed.
The ILC Articles purposely left open the question of whether states that are not directly injured by the breach, though bound by the obligation breached (‘indirectly injured states’), may resort to countermeasures. Article 54 states that:
This ‘savings clause’ was included because, at the time (in 2001), the ILC found that ‘[p]ractice on this subject [was] limited and rather embryonic’. The ILC referred to six instances where indirectly injured states appeared to be taking countermeasures in response to serious breaches of obligations protecting a community or collective interest. These obligations were owed to the international community as a whole (erga omnes) or to a group of states (erga omnes partes), such as the prohibitions on the use of force, genocide and apartheid.
Some have argued that things have moved on since the adoption of the ILC Articles and that there is now sufficient evidence of state practice and opinio juris to show the development of customary international law permitting those types of countermeasures. That evidence will be discussed below.
Countermeasures taken by indirectly injured states in response to breaches of erga omnes and erga omnes partes obligations will be referred to here as countermeasures ‘in the general interest’ or ‘general interest countermeasures’. They refer both to measures taken to help the injured state against breaches of such obligations and those seeking to protect individuals from violations committed by the responsible state against its own population.
There have been suggestions that states other than the injured state, including states not bound by the obligation breached and thus not indirectly injured by the breach (‘third states’), may take countermeasures in support of the injured state, irrespective of whether the obligation breached is of an erga omnes nature. One proposed scenario is where the third state would act as a surrogate or proxy for the injured state, taking itself the countermeasures that the latter is entitled to under international law. A similar proposition is that third states could take countermeasures jointly with the injured state.
A separate issue is whether third states may provide aid or assistance to the injured state. In this case, the third state is not itself taking countermeasures: it is simply providing some support to the injured state’s own countermeasures. For example, a third state could provide financial assistance, cybersecurity training, intelligence-sharing, defensive software or hardware, or have a more active, but secondary, involvement in cyber operations deployed as countermeasures by the injured state. Such assistance could be carried out in an ad hoc manner or in the context of cyber defence alliances.
This chapter seeks to assess whether and to what extent these different types of measures are lawful under international law today. This includes whether general interest countermeasures find support in sufficient evidence of state practice and opinio juris, including in the cyber context. This chapter will also look at whether third states may take countermeasures in support of the injured state, irrespective of the type of obligation breached. Finally, the chapter will discuss the extent to which third states may assist the injured state in taking its own countermeasures, in light of the existing principles on aid or assistance in the law of state responsibility.
Countermeasures in the general interest
General principles
As noted earlier, there have been suggestions that indirectly injured states may take countermeasures in the general interest in response to breaches of obligations erga omnes and erga omnes partes. According to the ICJ in the Barcelona Traction case, obligations erga omnes are ‘the concern of all states. In view of the importance of the rights involved, all states can be held to have a legal interest in their protection […]’. Examples include the prohibition on the use of force, human rights obligations, most rules and principles of international humanitarian law, the principle of self-determination, the prohibition of apartheid and slavery, and core international crimes (i.e. the crime of aggression, war crimes, crimes against humanity and genocide) – all of which are grounded in customary international law.
These overlap with obligations erga omnes partes, which arise for all states parties to a treaty protecting a collective interest. Unlike bilateral obligations in a multilateral treaty, breaches of erga omnes partes obligations are the concern of all states parties considered collectively, beyond their individual interests. As such, each state has a legal interest to stop and/or repair the violation. It is for states parties to a treaty to decide what such a collective interest is – irrespective of the number of states involved. Examples include regional human rights treaties, and treaties for the protection of the environment, regional security, nuclear materials or weapons, and the prevention of terrorism and other serious offences.
The mere fact that a state has a legal interest in upholding an erga omnes or erga omnes partes obligation does not automatically entitle it to take countermeasures. Article 49 of the ILC Articles recognizes the right of injured states – and those states only – to take countermeasures. Thus, if indirectly injured states have a right, under customary international law, to take countermeasures in the general interest, this right must come from general state practice accepted by states as law (i.e. opinio juris). Whether or not this is the case was controversial during the drafting and debates surrounding the ILC Articles and remains so today.
State practice and opinio juris
Following a decades-long negotiation process, the draft Articles proposed by James Crawford in 2000 recognized the right of indirectly injured states to take countermeasures in the general interest (in draft Article 54). But this was met with ambivalence or opposition from many states at the UNGA Sixth Committee, despite some voices in support. Objections were both legal and political. As noted earlier, some states argued that recognizing the right of indirectly injured states to take countermeasures would run contrary to the UN Security Council’s mandate to adopt collective enforcement measures. Others pointed to the risk of destabilizing treaty relations, and the difficulty of ensuring the proportionality of such measures. An argument was also made that the concept of erga omnes obligations remained too general or vague and was thus subject to abuse, especially by more powerful states. These objections, coupled with the paucity of examples of general interest countermeasures in state practice, led the ILC to finally adopt the savings clause in what is now Article 54.
The objections were indeed quite strong. They make it difficult to argue that, at the time the Articles were adopted in 2001, customary international law recognized the right of indirectly injured states to take general interest countermeasures (both in response to breaches of erga omnes and erga omnes partes obligations). At the same time, it is fair to say that state practice and the accompanying opinio juris have evolved significantly since 2001. The following examples have been pointed to as possible evidence of state practice in support of general interest countermeasures:
- asset freezes as well as trade and investment restrictions imposed on Myanmar by EU member states, the US, Switzerland and other states since the early 2000s, in response to human rights violations committed by Myanmar officials;
- asset freezes and trade restrictions adopted by the US and Switzerland against Libya, as well as Libya’s suspension from the Arab League, in response to the country’s human rights and humanitarian law violations during and following its repression of pro-democracy movements in 2011;
- asset freezes, trade restrictions, and civil aviation bans adopted by EU member states, the US, Australia, Switzerland, Canada, Turkey and Japan against Syria, as well as Syria’s suspension from the Arab League and the Organization of Islamic Cooperation (OIC), in response to the human rights and humanitarian law violations committed by the Assad regime since 2011;
- asset freezes, trade and investment restrictions, and civil aviation bans adopted by a variety of states, including EU and G7 member states, Australia, Iceland, New Zealand, Norway, the Republic of Korea, Singapore and Eastern European states (such as Serbia, Georgia, Moldova and Albania), as well as asset seizure in the case of Canada, against Russia in response to its occupation of Crimea (2014) and/or its full-scale invasion of Ukraine (2022);
- land, air and sea blockade imposed by Saudi Arabia and the United Arab Emirates against Qatar in response to its alleged support for international terrorism in 2017, in violation of the Riyadh Agreements;
- the ban on Belarussian airlines by the EU and its member states in response to Belarus’ unlawful diversion of a commercial aircraft flying from Greece to Lithuania in 2021, in violation of the Chicago Convention; and
- asset freezes and investment restrictions adopted by EU member states and Norway, the suspension of a bilateral agreement on international road transport by Norway and of the Treaty on Conventional Armed Forces in Europe by Poland against Belarus, in response to the latter’s support for Russia’s invasion of Ukraine.
In the cyber context, state action is mostly covert. Thus, it is often difficult to discern when states may be taking cyber countermeasures in the general interest. Nevertheless, within the growing tendency of states to form alliances or at least seek to coordinate their responses to malicious cyber operations, there is some evidence that they are employing cyber tools that are on their face unlawful under international law, and thus could constitute collective countermeasures.
For example, under the EU’s Framework for a Joint EU Diplomatic Response to Malicious Cyber Activities (or Cyber Diplomacy Toolbox), asset freezes may be taken in response to malicious ‘cyber activities targeting the integrity and security of the EU and its member states’ or that have ‘a significant effect against third states or international organisations’. Among these activities, the Toolbox’s ‘Revised Implementing Guidelines’ highlight cyberthreats arising in the context of or as ‘a result of Russia’s unjustified and unprovoked war of aggression’ – a serious breach of an erga omnes rule.
While these are significant developments, two challenges should be borne in mind when assessing this practice, both in relation to cyberspace and generally: i) unclear state practice, and ii) unclear opinio juris.
Unclear state practice
The available state practice is often unclear because states rarely characterize measures that are on their face unlawful as countermeasures – explicitly or implicitly. They tend to refer instead to ‘sanctions’, ‘restrictive measures’ or other non-legal concepts. Sometimes, states may prefer not to disclose the legal basis for their action, especially when they intend to reserve different arguments for litigation.
Furthermore, practice is sometimes deemed to constitute a countermeasure where it can be explained in other ways. For example, trade restrictions could have been adopted as Security Exceptions under the GATT (though to be valid, these must be specifically invoked by the state party in question). Moreover, in the absence of a trade agreement between the indirectly injured state taking the measures and the responsible state, trade restrictions would amount to retorsion. This might be the case of many trade restrictions adopted vis-à-vis Syria, Libya and Belarus insofar as these are not members of the WTO nor parties to the GATT, and in the absence of a relevant bilateral trade agreement.
There are, however, some exceptions. For example, in a research paper on Third-party Countermeasures under International Law, the European External Action Service (EEAS) concluded not only that general interest countermeasures are permitted under international law but also that EU sanctions against Russia following its invasion of Ukraine qualify as such. Following the publication of this paper, the Council of the EU decided to insert a recital in its decision to renew sanctions against Russia following its full-scale invasion of Ukraine. The recital states that:
Breaches of peremptory norms overlap with, but are narrower than, erga omnes or erga omnes partes obligations. They are rules from which no derogation is permitted, such as the prohibitions on the use of force, genocide and torture. While the decision to add the recital does not explicitly refer to countermeasures, the recital’s wording, and the reference to the EEAS paper, do seem to imply some degree of acceptance of the characterization of EU sanctions against Russia as general interest countermeasures.
Similarly, in a decision regarding EU restrictive measures against Russian broadcaster RT France, the Court of Justice of the EU characterized those measures as a ‘response […] of a subject of international law faced with aggression in breach of Article 2(4) of the United Nations Charter and, consequently, a violation of the erga omnes obligations imposed by international law’.
More explicitly, an Italian regional court concluded on the basis of the erga omnes nature of the obligations breached by Russia in its full-scale invasion of Ukraine, that ‘[t]he “restrictive measures” ordered by the [European] Union against the Russian Federation therefore have, in the context of international law, the legal nature of real countermeasures’.
And in a statement announcing a decision to suspend its obligations under the Treaty on Conventional Armed Forces in Europe (CFE), the US noted that:
However, like several other states, the US’s suspension of the CFE treaty was not characterized as a countermeasure, but as a fundamental change of circumstances.
Unclear opinio juris
Even where there is clear evidence that the measure in principle contravenes international law, the accompanying opinio juris may be inconclusive. This may happen when states do not view their measures as contrary to international law or do not think that they qualify as countermeasures, even if they do breach international law. It is particularly difficult to assess the opinio juris when states only present policy or domestic legal justifications for those measures. This difficulty is compounded because, as noted earlier, countermeasures often resemble other types of remedies under international law, such as unfriendly acts of retorsion, measures justified under specific treaties or treaty suspension – for instance, because there has been a fundamental change of circumstances or a material breach.
As far as asset freezing is concerned, some states do not view it as a violation of international law that requires justification as a countermeasure. This view is grounded in the assumption that the assets of foreign states or their officials do not enjoy immunity from executive or legislative acts, but only from judicial court proceedings. While this view is contested, it is still relevant for the assessment of the opinio juris of the state concerned. Even if states are wrong in their assessment of international law, their views do count as opinio juris. Therefore, if a state views its actions as lawful but they turn out to be unlawful, there would still be no opinio juris in support of their characterization as countermeasures.
The EU sanctions mentioned earlier illustrate this difficulty: most have not been labelled as ‘countermeasures’ and there are disagreements about their characterization among EU member states. For example, the EU Cyber Diplomacy Toolbox does not refer specifically to (general interest) countermeasures. And at least one member state – France – has explicitly rejected this characterization – as well as that of other joint cyber initiatives.
To be sure, countermeasures must be assessed objectively, regardless of their framing. And it may be possible to derive or deduce opinio juris from state practice, i.e. the actual countermeasure. For instance, compliance with the substantive and procedural conditions for the taking of countermeasures, such as the identification of a prior breach of international law or a prior demand, might indicate that the measure in question is indeed regarded by the state as a countermeasure. Likewise, if there is no publicly available evidence that the acting state considers the measure to be a lawful act of retorsion, a treaty-specific exception, or admittedly unlawful, it may be reasonable to infer that the measure is a countermeasure. The same is true if the acting state has in the past justified a similar action as a countermeasure.
As a public-facing claim, the opinio juris of states can only be assessed by reference to publicly available materials, as opposed to the subjective views or intentions of particular state agents that are kept out of the public eye. The necessary opinio juris may be supplied by state acts such as a court pleading, domestic legislation, a domestic court decision or a public statement, including a national position on international law in cyberspace. Furthermore, the reactions of other states, including their silence, may count as their own opinio juris in support of the practice in question. State silence is legally relevant to the formation of customary international law when the actions of a state are public and call for a reaction from other states.
Nevertheless, opinio juris is ultimately a subjective element – a ‘subjective attitude to [the] behaviour’. Thus, if there is evidence that the state concerned did not consider that its actions in principle violated international law such that they would require justification, or that the state actually intended to act unlawfully, the necessary opinio juris would probably be lacking for the state practice in question. And if the evidence of state practice or opinio juris is inconclusive, support for the development of a new rule of customary international law cannot be presumed, especially when such a rule would encroach upon the rights of other states, as is the case of general interest countermeasures. In most of the examples assessed above, which have been cited as supporting general interest countermeasures, it appears that the states in question did not consider themselves to be taking general interest countermeasures. Importantly, many states, including Russia, China, Iran and Brazil, have continued to object to the taking of countermeasures by indirectly injured states, including in the case of serious breaches of erga omnes and erga omnes partes obligations.
To be sure, some states have expressed support for general interest countermeasures in their national positions or statements on international law in cyberspace, which, as noted earlier, could be evidence of their opinio juris on the matter. At the time of writing, this is the case of Estonia, Ireland, Poland and Costa Rica.
Estonia has taken an expansive view by ‘furthering the position that states which are not directly injured may apply countermeasures to support the state directly affected by the malicious cyber operation’.
For Ireland, ‘on the question of third party or collective countermeasures, […] since the adoption of the ARSIWA in 2001, state practice indicates that such measures are permissible in limited circumstances, in particular in the context of violations of peremptory norms.’
Likewise, Poland has recognized that ‘the evolution of customary international law over the last two decades provides grounds for recognising that a state may take countermeasures in pursuit of general interest as well’. For Poland, this includes, ‘[i]n particular, […] measures […] in response to states’ violations of peremptory norms, such as the prohibition of aggression.’
Costa Rica’s view is that ‘countermeasures may be taken by the injured state, i.e. the State specifically affected by the breach, as well as third states in response to violations of obligations of an erga omnes nature or upon request by the injured State.’
However, at least two states have rejected the concept of general interest countermeasures when expressing their views on international law in cyberspace. One is Canada, which has not found, ‘to date, […] sufficient State practice or opinio juris to conclude that [collective cyber countermeasures] are permitted under international law’. Similarly, in France’s view, ‘collective counter-measures are not authorised, which rules out the possibility of France taking such measures in response to an infringement of another state’s rights’. Admittedly, this statement seems to focus on bilateral as opposed to erga omnes obligations. But in a more recent statement, France noted that it does not recognize ‘collective countermeasures’ generally, making no distinction between the different types of breaches to which they might respond.
Other states are more ambivalent on the matter. For example, while Denmark recognizes that ‘[t]he question of collective countermeasures does not seem to have been fully settled in state practice and needs careful consideration’, the country seems open to the concept of general interest countermeasures:
Similarly, while not referring explicitly to general interest countermeasures, the UK has taken the view that ‘[i]t is open to States to consider how the international law framework accommodates, or could accommodate, calls by an injured State for assistance in responding collectively.’ New Zealand is also ‘open to the proposition that victim states, in limited circumstances, may request assistance from other states in applying proportionate countermeasures to induce compliance by the state acting in breach of international law’.
This range of views means that, at present, it is difficult to establish the necessary opinio juris in support of the lawfulness of general interest countermeasures under customary international law.
Assessment
In light of the above, there seems to be insufficient state practice and opinio juris in support of a right of indirectly injured states to take general interest countermeasures under customary international law. However, there is clear evidence that a few states, particularly in the West, consider that the law has evolved since 2001 such that it now permits general interest countermeasures in response to breaches of erga omnes and erga omnes partes obligations, whether in support of an injured state or in response to violations affecting the responsible state’s own population. Those states have acted accordingly and have made public their views on the matter. The practice in support of general interest countermeasures not only continues to evolve but seems to be the general direction of travel in customary international law, spearheaded by some EU member states in particular. The impetus for this development is not only the cyberthreat landscape but also the Russian invasion of Ukraine. For many, this state of flux may be unsatisfactory. But it falls on states to make their views public and clear, in one way or another. If lawful, general interest countermeasures ought to be subject to the same substantive and procedural conditions applicable to countermeasures taken by the injured state and assessed in Chapter 2.
Countermeasures by third states
General principles
There have been suggestions that third states, including non-injured states, are entitled to engage in yet another category of countermeasures in support of the injured state, irrespective of the nature of the obligation breached. For instance, as seen earlier, Estonia has furthered the position that ‘states which are not directly injured may apply countermeasures to support the state directly affected by the malicious cyber operation’. For Estonia, just like self-defence, countermeasures ‘can be either individual or collective’. Costa Rica’s national position might be read in the same way: ‘countermeasures may be taken by […] third States […] upon request by the injured State’.
The concept seems to originate from Crawford’s draft Article 54(1), entitled ‘Countermeasures on behalf of an injured State’. However, this draft provision was rejected by governments and referred to countermeasures taken in response to breaches of erga omnes or erga omnes partes obligations.
As a general matter, countermeasures operate bilaterally between the injured and the responsible state: they preclude the wrongfulness of the former’s actions vis-à-vis the latter. The injured state cannot simply delegate its right to take countermeasures or share circumstances precluding wrongfulness with another state, as this would encroach upon the rights of the responsible state. Furthermore, each state is normally responsible for its own conduct and entitled to its own defences under international law. While there is some support in scholarly writings for such a delegation of power or sharing of defences, sufficient evidence of state practice and opinio juris that this is permitted under international law would be required. This evidence is lacking.
The majority of experts involved in the drafting of the Tallinn Manual 2.0 concurred with this view, which resulted in the adoption of the following rule: ‘Only an injured State may engage in countermeasures, whether cyber in nature or not.’
Assessment
At present, there is no separate legal basis under customary international law allowing third states to take countermeasures in support of the injured state, even with the latter’s consent. The legality of measures taken by a third state depends on a) whether this state is independently entitled to take countermeasures against the responsible state, and b) whether general interest countermeasures are lawful, and the measure seeks to respond to a breach of an erga omnes or erga omnes partes obligation.
Aid or assistance to an injured state
Irrespective of whether countermeasures may be taken by states other than the injured state, there remains the question of whether those states may lawfully provide aid or assistance to the injured state in taking its own countermeasures. For example, a third state might assist the injured state by providing intelligence about the location of the servers and other infrastructure used by the responsible state to commit a wrongful cyber operation; the injured state may then use this information to launch a countermeasure against the responsible state.
General principles
In assessing this question, the starting point is Article 16 of the ILC Articles, which provides that:
Underpinning this provision is the idea that the responsibility of the assisting state is ancillary to that of the receiving state. This means that even if the act of assistance is per se lawful, the fact that the assisting state is providing support to a wrongful act ‘taints’ the assistance with illegality. The assisting state will be responsible for its acts of assistance if: i) it has ‘knowledge of the circumstances of the internationally wrongful act’ that it is aiding; ii) the assistance significantly contributed to the wrongful act; and iii) the underlying act to which the assistance is provided is wrongful for the assisting state (i.e. the assisting state must also be bound by the obligation breached by the receiving state).
Insignificant contribution
In line with Article 16(a) of the ILC Articles and point ‘ii’ above, it is uncontroversial that any assistance to a countermeasure that does not make a significant contribution to that countermeasure will not engage the responsibility of the third state. This level of assistance will fall below the threshold set by Article 16 for the causal nexus between the assistance and the underlying wrongful act. An example is when the third state provides intelligence about the origin of an unlawful cyber operation to the injured state, yet the latter chooses not to use such information in its response against the responsible state, such as by taking non-cyber countermeasures.
Breach of obligations not owed to the responsible state
Likewise, per Article 16(b) of the Articles and point ‘iii’ above, if the third state is not bound by the obligation breached by the injured state’s countermeasures, any assistance given by the former to the latter would fall outside the scope of Article 16. For example, if the countermeasure amounts to the breach or unlawful suspension of a bilateral investment treaty between the injured state and the responsible state, and the third state is not otherwise bound by the same rule, its assistance will not be unlawful, even if it makes a significant contribution to the injured state’s countermeasures. This is an expression of the pacta tertiis principle, according to which international obligations cannot bind states that have not agreed to them.
Unlawful assistance to a countermeasure
On the other hand, if the assistance is itself unlawful, i.e. if it breaches an obligation owed by the third state to the responsible state, then it will independently engage the responsibility of the third state. Using the same scenario as above, the provision of intelligence would be unlawful for the third state if it had concluded an agreement with the responsible state prohibiting the gathering or sharing of intelligence about the responsible state’s conduct. Similarly, by adopting a trade restriction against the responsible state to support the injured state, the third state could breach an obligation owed to the responsible state under a bilateral or multilateral trade agreement. These types of cases fall outside the scope of aid or assistance under Article 16 of the ILC Articles. An act of assistance that in and of itself breaches obligations owed to the responsible state already engages the responsibility of the third state for its own wrongdoing. In this case, the assisting state cannot use the injured state’s justification to take countermeasures.
Lawful assistance to a countermeasure
However, nothing stops the third state from providing lawful assistance to a countermeasure, i.e. assistance that does not involve the breach of an obligation owed by the third state to the responsible state. Examples include the provision of funds, intelligence, training or equipment if doing so does not otherwise violate obligations owed by the third state to the responsible state. One simple way to look at this question is to consider that a lawful countermeasure is not an internationally wrongful act in the sense of Article 16. As such, Article 16 would not be implicated: it would not impose any ancillary responsibility on the third state by reason of its assistance to the injured state. This means that, if the injured state’s countermeasures are lawful, i.e. if they meet all the substantive and procedural conditions assessed in Chapter 2, then there is no wrong in which the third state can be complicit.
Others have pointed to an alternative line of thinking that might reach the same result. In essence, the argument is that, though countermeasures are in principle wrongful acts falling within the scope of Article 16, the injured state’s defences could be shared with the third state by virtue of the latter’s ancillary responsibility. There has been some debate about whether countermeasures are justifications applying objectively to the conduct of the injured state (and are thus transferable to other states) or agent-specific excuses benefitting the injured state exclusively. It is arguable that countermeasures are justifications, such that the third state could, under this view, make use of this defence.
Some of the Tallinn Manual 2.0 experts agreed with the view that states may provide lawful assistance to countermeasures generally and in cyberspace. This view seems to be echoed in Canada’s national position on international law in cyberspace. For Canada, ‘[a]ssistance can be provided on request of an injured State, for example where the injured State does not possess all the technical or legal expertise to respond to internationally wrongful cyber acts.’ Denmark also seems to favour this type of aid or assistance, noting that ‘there may be instances […] where the victim State may request the assistance of other States in applying proportionate and necessary countermeasures in collective response hereto’.
Assistance to unlawful countermeasures
Providing assistance to a countermeasure is not the same as taking a countermeasure. Therefore, it is the responsibility of the injured state to comply with the conditions for the taking of countermeasures under customary international law. Yet, under Article 16 of the ILC Articles, the third state may be responsible for its assistance to the injured state if: i) the injured state does not observe the strict conditions governing the taking of countermeasures, such that the action taken by the injured state constitutes an internationally wrongful act, ii) the third state knows that the action by the injured state will not satisfy, or does not satisfy, the conditions for taking countermeasures; and iii) the other conditions for aid or assistance under Article 16 are met, i.e. the assistance is a significant contribution to the internationally wrongful act, and the act that the third state is assisting would be internationally wrongful if committed by that state.
In light of the ILC commentary to Article 16 and its drafting history, ‘knowledge’ is best understood as deliberate assistance with near certainty or wilful blindness of the underlying act’s wrongfulness, present at the time the assistance is provided or while it is ongoing. However, assistance will usually be provided before the injured state is taking its own (counter)measures, and, in reality, one can hardly be certain about future events. On this basis, the third state will be responsible if it knows with near certainty or deliberately disregards evidence that its assistance will make, is making or has made a significant contribution to measures that are on their face unlawful and do not meet the conditions for the taking of countermeasures, and nonetheless chooses to provide or continue to provide help anyway.
This could be the case, for example, when the third state provides financial assistance to an injured state ahead of the latter’s measures knowing or wilfully disregarding that such measures are not intended to stop and/or repair an internationally wrongful act, that they would be disproportionate to the prior wrong, or could not meet the other conditions for the taking of countermeasures. Likewise, the third state may be responsible under Article 16 if its significant contribution is provided simultaneously with or after the relevant measures are taken by the injured state, and the third state knows or wilfully disregards the fact that those measures have not been taken following a prior demand, or have not met the other conditions for the taking of countermeasures.
If the countermeasures taken by the injured state are initially lawful, but for some reason fail to meet any of the relevant conditions, the third state will be liable for wrongful aid or assistance if it finds out about or wilfully disregards such illegality and nonetheless continues to provide assistance to the injured state. For instance, if the prior wrong has stopped and the dispute between the injured and responsible state is pending before a competent court or tribunal, or if the responsible state has made reparation for the wrong, the third state may need to stop its assistance to the countermeasures taken by the injured state. Otherwise, if the third state knows or wilfully disregards these facts, and continues to significantly support the injured state, it may be held responsible for assisting an internationally wrongfully act under Article 16.
In practice, to avoid responsibility, the third state will need to consider the risks of violating Article 16 in advance of providing assistance to the injured state and while the assistance is ongoing. This includes consideration of how the assistance will be used by the injured state, i.e. if it will be specifically used for a countermeasure or just as a form of general support (for example, to help the injured state decide about its response options), or to inform a measure of retorsion. The third state also needs to consider the prospect that the injured state will enforce the countermeasure in accordance with the conditions applicable under customary international law. This demands a certain degree of due diligence on the part of the third state, including an ongoing risk assessment of the situation informed by a number of contextual factors, such as the third state’s relationship with the injured state, the injured state’s previous behaviour, including its track record of compliance with international law, and any assurances by the injured state that it will observe international law when taking countermeasures.
Assessment
In sum, the analysis above suggests that, under the customary international law rules of state responsibility, third states may provide assistance to an injured state’s countermeasures insofar as the assistance does not violate the obligations independently owed by the third state to the responsible state or Article 16 of the ILC Articles. Article 16 will not be violated if: i) the assistance does not significantly contribute to the countermeasure or ii) the third state is not bound by the obligations breached by the injured state’s countermeasures. Otherwise, states should take precautions to avoid violating Article 16 by knowingly assisting in the taking of countermeasures that fail to meet the substantive and procedural conditions set under customary international law.
