1. Introduction
The existence of a ‘dispute’ can be a requirement for the jurisdiction of numerous international courts and tribunals (ICTs).Footnote 1 This requirement’s objective is to protect the judicial function and the parties from moot cases;Footnote 2 to distinguish the ICTs’ contentious from advisory functions; and, as far as permanent courts are concerned, to promote their efficiency in delivering justice.Footnote 3 For the jurisdiction of numerous ICTs, a dispute must exist prior to filing the application,Footnote 4 irrespective of whether prior recourse to other settlement is required.Footnote 5 Thus, only facts that took place prior to the date of application can be relied on as evidence that a dispute existed.
A dispute may be generated over time by state actions, statements, inactions and silences – at times, in direct exchange with each other, and on other occasions, independently from each other. But, for a dispute to exist, it must be shown that the claim of one party is positively opposed by the other.Footnote 6
Yet, when a state directs a claim at another state, and the latter state fails to respond, it is far from evident that the silent state opposes, let alone positively opposes, the claim.Footnote 7 Behind silence, there can be a whole array of possible reasons; not a binary choice of motivations – ‘I agree’/‘I disagree’. For instance, a state’s position is usually formulated by multiple individuals, committees and departments. Until a position, which the state can express, is formulated internally, that state will be externally silent. Additionally, silence may be intended to provide a cooling-off period, so that a dispute does not arise and good relations are maintained. Further, a state may agree with the law’s interpretation by another state, but not with the facts that the latter state complains of.
However, ICTs have developed and apply an inference of opposition and of a dispute from or despite state silence. This inference is biased in favour of establishing a dispute, over any other meaning (or the lack of meaning) that silence may have.Footnote 8 The reasoning behind the inference and its potential critics are connected to and have wider implications for the function of international adjudication and its place in international affairs.
On one view, the inference of a dispute from state silence favours the ‘international rule of law’, namely that international rules are meant to be applied and enforced by ICTs,Footnote 9 which is an aspect of the public function performed by international adjudication. Intimately connected to this reasoning is that states cannot be allowed unilaterally to control an ICT’s jurisdiction.Footnote 10 Further, proponents of the school of thought of the public function of international adjudication may agree with those who argue that introducing formalism for the establishment of a dispute and of jurisdiction, would hinder applicants from accessing justice.Footnote 11 For them, there is no need to introduce conditions for silence to mean opposition.
On another view, ICTs perform a private function: the resolution of disputes between the litigants to which the latter have consented.Footnote 12 Clauses, which require the existence of a ‘dispute’, form the basis upon which states consent to submit themselves to an ICT’s jurisdiction. As the United States (US) argued in Ecuador v. US, projecting on a respondent’s silence the meaning of opposition, when there is no opposition, exceeds the respondent’s consent, insofar as no real dispute exists,Footnote 13 and departs from the voluntarist basis of international adjudication. The latter departure may lead states to lose belief in international adjudication.Footnote 14
Further, critics of the inference of a dispute from silence might argue that, by favouring international adjudication, the inference encourages disputes, in order for litigation to take place. They might also contend that the inference reflects a bias in favour of international adjudication over non-judicial means of settlement, even though adjudication is ‘simply an alternative to the direct and friendly settlement … between the parties’.Footnote 15 Once a claimant addresses a claim at another state, an ICT’s jurisdiction is established, simply because the addressee has not responded to the claim, even if the addressee has offered informal discussions. For instance, in South Africa v. Israel (2024), South Africa alleged in its Note Verbale that Israel committed genocide in Gaza. Israel responded by offering discussions.Footnote 16 In South Africa’s view, since Israel did not address South Africa’s claim, a dispute and the ICJ’s jurisdiction had been established.Footnote 17
Despite its extraordinary consequences for international adjudication, state silence as opposition has mostly escaped scholars’ attention,Footnote 18 who have, instead, focused on acquiescence.Footnote 19
This study argues that a dispute can and should be inferred from silence under specific conditions.Footnote 20 First, a state must remain silent (Section 2). Second, the silence must be in response to a claim by another state (Section 3). Third, the claim must be made in circumstances that call for the silent state’s reaction: (i) the claim must be such as to call for the reaction of the silent state; (ii) the silent state must be aware of the claim and be in a position to react (Section 4). Fourth, reasonable time of silence must pass from when the awareness requirement is met (Section 5). The dispute’s inference should not be drawn only when no ‘other reasonable explanations’ for silence exist (Section 6).
The study considers all decisions, as of 29 February 2024, of the ICJ, the International Tribunal for the Law of the Sea (ITLOS), tribunals under Annex VII of the United Nations Convention on the Law of the Sea (LOSC), and inter-state investment tribunals under the Permanent Court of Arbitration (PCA).Footnote 21 It relies on the 15 decisions where the inference of a dispute from silence was pleaded, relied on or mentioned by the ICTs (Table 1, below).Footnote 22 It also relies on state practice in the form of pleadings in the aforementioned 15 decisions, which although minimal, is geographically representative.Footnote 23 The individual opinions of judges and arbitrators offer guidance and critical analysis of the judicial decisions.
Reasoning in ICT Decisions as to the Existence of a Dispute
There is no suggestion in judicial decisions, state practice, scholarship or by judges that the inference of a dispute and its conditions are based on customary international law or a general principle of law. However, it can be argued that state pleadings support custom and/or a general principle of law in this respect, strengthened by the reasoning of ICTs.Footnote 24 Alternatively, it can be argued that the decisions of ICTs interpret the term ‘dispute’ in the treaty-based or unilaterally expressed consent of states.
In any event, where state practice and judicial decisions offer little support for a particular condition, the analysis relies on normative reasoning that conforms to principles of international law, such as good faith, and on reasoning that is in harmony with international jurisprudence.
Section 7 concludes that the inference of a dispute from silence must be encouraged, and the conditions for inferring a dispute from silence should be retained in international adjudication. The inference prevents the tactical ‘weaponization’ of one’s silence in order to undermine international justice. Further, the conditions, under which the inference can be made, address the two schools of thought about the inference and international adjudication. They perform primarily an evidentiary function. Because silence can only be interpreted to mean opposition, when a particular context is present, the conditions ensure high probability that the silent state rejects the claim, and that not all instances of silence entail that a dispute exists. They thus address the criticism that voluntarism may be undermined. At the same time, because they are the necessary interpretative context of silence, the conditions are a matter of substance, not a formality. Even assuming arguendo that the conditions introduce some degree of formalism for evidentiary purposes, they also perform two additional subsidiary functions: a cautionary and a channelling function.Footnote 25 In a field, such as international law, where party autonomy is a default, the conditions ensure that a claiming state and the claim’s addressee are being cautioned that, by making claims of particular quality, the claiming state generates a legal process, which can lead to a dispute (cautionary function). Additionally, the conditions indicate that a particular legal process – a ‘dispute’ – is being generated, as opposed to any other legal process, such as international law-making or state responsibility, where silence can, instead, mean acquiescence (channelling function).
2. A state’s failure to respond
Here, ‘failure to respond’ or ‘silence’ concerns the absence of a state’s oral or written speech act, when it is combined with lack of change of the silent state’s conduct. A state’s silence may be complete or thematic.Footnote 26
Complete silence involves instances where a state does not respond at all to another state’s views. An example discussed below is Myanmar’s silence in response to Gambia’s Note Verbale alleging that Myanmar violated the Genocide Convention (Gambia v. Myanmar).
However, state behaviour operates along a continuum between complete silence and responsive speech. A state may use ‘non-responsive speech’: it may speak without taking a position on a claim made by another state. Such instances constitute ‘thematic silence’.
For instance, in Cameroon v. Nigeria (1998), which partly concerned territorial boundary delimitation, Nigeria objected to the Court’s jurisdiction claiming that Nigeria never took a position about Cameroon’s claims, and thus a dispute did not exist prior to Cameroon filing the application.Footnote 27 During the oral proceedings, the Court asked Nigeria whether its claim that a dispute did not exist signified that there was agreement between Cameroon and Nigeria.Footnote 28 Nigeria responded, but did ‘not indicate whether or not it agrees with Cameroon’.Footnote 29
In South China Sea Arbitration (2015), China had regularly communicated to the Philippines its views about its ‘historic rights’, its ‘nine-dash line’, and that ‘China’s Nansha Islands [are] fully entitled to Territorial Sea, [EEZ] and Continental Shelf’. However, China did not clarify some legal issues about these claims that the Philippines had taken a view on.Footnote 30
In Georgia v. Russia (2011), Russia’s Minister of Foreign Affairs made a statement, from which, along with other statements in the United Nations (UN) Security Council, the ICJ inferred a dispute between Georgia and Russia.Footnote 31 The statement of Russia’s Minister commented on Georgia’s allegations against Russia, but did not condemn them or take a position on them.Footnote 32
Finally, in South Africa v. Israel, South Africa alleged inter alia in a Note Verbale that Israel committed genocide in Gaza. Israel responded to the Note Verbale requesting discussions with South Africa, but did not take a position on South Africa’s allegation.Footnote 33
State practice and decisions of ICTs do not adopt the term ‘thematic silence’, although they have relied on instances of thematic silence when assessing whether a dispute exists.Footnote 34 This study relies on cases involving complete or thematic silence to argue that opposition can be inferred in either situation. Further, because speech is the immediate context of thematic silence, this context may prove that the silent state is aware of another state’s claim (Section 4.2) or that the silent state is not otherwise impaired from reacting (Section 4.3).
3. A claim
Since Georgia v. Russia (2011), the ICJ considers that ‘the existence of a dispute may be inferred from [a state’s failure] to respond to a claim in circumstances where a response is called for’.Footnote 35 The Court’s reasoning is compatible with its jurisprudence that in order for a dispute to exist, it must be shown that a state’s claim is positively opposed by another state. Other ICTs have since followed the same reasoning.Footnote 36
A dispute can be inferred from silence in response to a claim, which:
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1. concerns a breach or expresses views about matters other than a breach of international law;
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2. uses assertive language;
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3. is about the silent state’s conduct or view and is made by statement;
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4. is communicated externally.
These circumstances perform primarily an evidentiary function, but also cautionary and channelling functions.
3.1. The claim may concern a breach or not
Most instances of inter-state litigation concern disputes that involve allegations of a breach of international law. However, states may have opposing views about matters that do not concern a breach. A state’s claim may concern territorial title, maritime delimitation, whether a state is or not party to a treaty, whether a reservation is valid, or the identification or interpretation of international law.Footnote 37
In the absence of a compromissory clause, which restricts an ICT’s jurisdiction to disputes concerning the application of the law and/or to claims regarding a breach, a ‘dispute’ can be established by claims that do not concern the breach of a rule. Numerous decisions support this position.Footnote 38 For instance, in Ecuador v. US, the US argued that there was no dispute, because, under general international law, a ‘dispute’ requires an allegation of breach, and Ecuador did not claim a breach in this case.Footnote 39 The Tribunal, whose jurisdiction under the 1993 Ecuador-US BIT covered ‘disputes … concerning the interpretation or application of the Treaty’, found that no dispute existed. However, it did not do so on the ground that the applicant’s claim did not concern a breach.Footnote 40
3.2. The claim uses assertive language
The claim (to which another state remains silent) must use assertive language. Speculative positions or exhortations do not make a legal claim. As shown below, state practice and case law supports this condition. The reasoning behind it is that a state should be expected to react to a concrete and clear claim (Section 4.1.2).
When the claim alleges a breach of international law, it must condemn the conduct of the addressee. For instance, in Marshall Islands, the ICJ reasoned that there was no dispute between the Marshall Islands and each respondent, partly because one of the statements of the Marshall Islands in the United Nations General Assembly (UNGA) meeting on Nuclear Disarmament was:
formultated in hortatory terms and [could not] be understood as an allegation that the [respondent] (or any other nuclear power) was in breach of any of its legal obligations. It does not … say that the nuclear-weapon states are failing to meet their obligations in this regard.Footnote 41
Where the claim does not concern a breach, some state practice supports that the claim must be assertive. For instance, in Mauritius/Maldives, both Maldives and Mauritius supported that claims must be assertive, rather than speculative.Footnote 42 Although the Chamber did not specifically comment on this matter, it reasoned that the Maldives were called to respond to Mauritius’ invitation to negotiate taking into account also the earlier claims of Mauritius, which were assertive.Footnote 43 Further, as it will be shown in Section 4.1.2.2 below, in relation to instances that do not concern a breach, the claiming state must articulate not only its own views but also the diverging views of the state that later remains silent (unless the silent state has communicated its views earlier). The latter can only happen if the positions are set out in assertive language.
3.3. A claim about another state’s conduct or view made by statement
ICTs reason that for a dispute to exist, it must be shown that the parties hold ‘positively opposed’ claims. However, there is lack of clarity and disagreement as to the evidence of a claim. Scholars agree with Judge Morelli’s proposition that a dispute exists when the ‘manifestations of will’ of the parties oppose.Footnote 44 Two independent or in exchange express manifestations of will suffice.
But, Morelli also argued, with some subsequent support, that conduct can manifest a claim; hence two diverging conducts or the conduct of one state followed by another state’s complaint establish a dispute.Footnote 45 Abi-Saab disagrees. For him, mere conduct cannot manifest a legal claim.Footnote 46 This reasoning leads him to argue that a ‘dispute’ does not (yet) exist, when the conducts of two states diverge;Footnote 47 and that, when a state’s conduct is complained of by another state, a dispute does not yet exist, because the claim of one state cannot alone establish a dispute.Footnote 48
It is argued here that, even if conduct is, in principle, capable to manifest a claim, a dispute can be inferred from silence only when silence ‘responds’ to a claim that concerns the other state’s conduct or views. Because the claim must have this content, it can only be made expressly, as explained below.
For instance, take a situation where State B allegedly violates its human rights obligations. State A suspends trade obligations vis-à-vis State B. State A’s trade restriction alone without some explanation (even in domestic law) does not express State A’s claim that State B violates its human rights obligations. State A’s trade restriction might manifest its view that its own conduct is lawful, for instance, because the primary rules permit it or because defences apply. The silence of State B in response to State A’s trade restrictions could mean acquiescence to State A’s allegedly wrongful trade restriction or waiver of a claim against State A. It does not necessarily mean that State B opposes an alleged view of State A that State B violated its human rights obligations. Instead, an express claim by State A complaining about the conduct of State B (that then remains silent) channels the legal process: a dispute is being generated between State A and B, instead of acquiescence being generated vis-à-vis the conduct of State A.
When the claim concerns the claiming state’s own entitlement or interpretation of the law, the claim must also explain that the other state’s views differ from its own (Section 4.1.2.2). For example, State A adopts and enforces domestic legislation determining the outer limits of its continental shelf. State B, which is a coastal state opposite to the coast of State A, but has not adopted legislation that makes a claim that overlaps with that of State A, becomes aware of State A’s legislation but does not respond. If State A does not also claim that State B’s views about their continental shelves deviate from State A’s claim, the silence of State B in response to the claim of State A may mean acquiescence. Instead, when the claim is about State A’s own entitlement and about the other state’s deviating position, the silent state agrees that its position deviates and thus opposes the claim of the claiming state.
This reasoning is supported by the four cases that involved claims unconcerned with breaches. For instance, in Cameroon v. Nigeria, Cameroon explained its position that its boundary with Nigeria was established based on numerous treaties, and articulated what it considered to be Nigeria’s claims over Bakassi Peninsula and elsewhere.Footnote 49 The ICJ considered that Nigeria’s silence as to its position regarding the whole boundary did not vitiate the dispute’s existence.
In Ecuador v. US, Ecuador by Note Verbale stated its understanding of what the correct shared interpretation of the Bilateral Ecuador-US Investment Treaty was. It also asked the US to ‘confirm, by a note of reply, the agreed upon [interpretation]. If such a confirming note is not forthcoming or otherwise [the US] does not agree with the interpretation of [the Treaty] by [Ecuador], an unresolved dispute must be considered to exist’ concerning the interpretation of the BIT.Footnote 50 The US confirmed receipt of the Note Verbale and indicated that it will respond in the future. The Tribunal found that there was no dispute, because silence could not be interpreted as opposition in this case. However, the Tribunal did not consider that Ecuador’s claim in the Note Verbale was unclear.Footnote 51
In South China Sea, the Tribunal did not address this issue. However, the Philippines had complained to China about some of China’s alleged entitlements.Footnote 52
Finally, in Mauritius/Maldives, Maldives in its submission to the Commission on the Limits of the Continental Shelf (CLCS) had made claims about its continental shelf. After assuring Mauritius that it would amend its submission to consider Mauritius’ claim, Maldives did not amend its submission,Footnote 53 and Mauritius protested. The ITLOS Special Chamber considered that Maldives were silent towards Mauritius’ ‘invitation to discuss about the maritime delimitation’ (eight years after Mauritius’ protest), and reasoned that these were circumstances calling for Maldives’ response.Footnote 54 In its ‘invitation’, Mauritius had not explained how its own and Maldives’ claims opposed. However, the context – namely, the earlier exchanges between the parties and the fact that both states had adopted domestic legislation making overlapping claims – made clear the parties’ individual claims.
Overall, silence in response to conduct alone is unlikely to mean positive opposition, because conduct might make an implied claim that one’s own conduct is lawful or irrespective of whether it makes an implied claim, silence in response to it may mean acquiescence. Thus, a claim about someone else’s conduct or views can only be made by statement, rather than by mere conduct. The claim’s quality and form perform a channelling function. Silence in response can mean opposition rather than acceptance.
However, this does not mean that prospective parties to the dispute must negotiate, where there is no such express requirement.Footnote 55 When there is a requirement for negotiations, and these are exhausted without settlement, a dispute necessarily exists. If prior negotiations are not required, prior exchanges may help show that a dispute exists.Footnote 56 For instance, the ICJ rightly reasoned that unco-ordinated manifestations of will communicated expressly and publicly established prima facie a dispute: a statement made by South Africa in the UNGA (alleging Israel committed genocide) and a separate statement of Israel communicated through a public website of Israel’s defence ministry (condemning any allegation of genocide).Footnote 57
However, for opposition and a dispute to be inferred from silence, silence must be in response to a prior claim. Silence is thus necessarily seen as part of an ‘exchange’. Unilaterally communicating one’s claim either directly and bilaterally, for instance, by sending a Note Verbale, making expressly the claim in a multilateral forum or other modes discussed in Section 4.2, suffices.Footnote 58
3.4. The claim must be communicated externally
A state’s claim must be expressed externally: publicly or privately and/or confidentially to another state. No decision inferred a dispute from silence in response to views communicated only between organs of the claiming state.Footnote 59 Further, no state has argued in favour of such proposition. Views communicated only between the internal organs of one state may indicate an ‘intention’, but do not constitute a claim.
Separately, that the claim must be externally communicated is distinct from, but consistent with, the requirement of awareness, examined in Section 4. Internal communications between state organs do not call for another state’s response, even when the silent state is actually aware of them.
4. Circumstances calling for a state’s response
State practice and ICTs decisions generally support that, for silence to mean opposition, a claim must exist in ‘circumstances calling for a state’s response’.Footnote 60 No decision has spelt out which are these circumstances. State and judicial practice support to varying degrees that the following cumulative circumstances call for another state’s reaction:
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1. Circumstances that concern the claim:
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(i) The claim is directed at the state that then remains silent;
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(ii) The claim is of ‘sufficient clarity’;
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(iii) The context supports the above;
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2. The state that remains silent is aware of the claim;
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3. The silent state is ‘in a position to react’.
These are discussed in detail below. When there is little support in state and judicial practice for the aforementioned contextual factors, the normative reasons in favour are explained.
4.1. Circumstances that concern the claim
4.1.1. The claim must be addressed at the state that then remains silent
ICTs do not clearly draw a distinction between those to whom the statement is communicated (‘addressees of the statement’) and those at whom the claim is directed (‘addressees of the claim’).Footnote 61 Yet, a claim directed at one state can be contained in a statement addressed to a bigger group of states that may or may not include the state against which the claim is directed. The paradigmatic example is a statement in the UNGA or intergovernmental conferences. Further, a statement may be addressed to a third state(s) or an international organization (IO), while the claim’s addressee may be a third state.Footnote 62 Alternatively, a statement may be made to the press thus addressing the wider public, but the claim contained in that statement is directed at a particular state.Footnote 63
The potential mismatch between the statement’s addressee and the claim’s addressee is the consequence of diplomacy and human communication. A state may intend to raise awareness among other states or IOs or among the wider public about its claim against another state. The goal may be to make its cause heard by the statement’s addressee(s) and to undermine the reputation of the claim’s addressee, in order to achieve economic or political advantages or to convince the claim’s addressee to resolve the dispute through non-judicial means or to submit itself to an ICT’s jurisdiction.
However, the claim must be directed at the state, which then remains silent. This condition is separate from awareness (Section 4.2). It is justified by good faith. A state can only be expected to react when it is clear to an objective observer that a claim is directed at that state.
The claim’s addressee is the entity whose legal interests are directly affected by the claim. A statement may expressly refer to the state or group of states at which the claim is addressed.Footnote 64 When it does not, the claim’s addressee can be identified by interpreting the unilateral statement, relying on the statement’s text in its context.Footnote 65
If the claim alleges a breach, the claim’s addressee is the state or states whose conduct is being criticized. Footnote 66 Separately, the reference to the alleged conduct will also meet the distinct requirement that the claim must be of ‘sufficient clarity’ (Section 4.1.2.1).
When the claim does not allege a breach, the claim is directed at the state that is affected by the claim. When a state makes a claim regarding the interpretation of a bilateral treaty, the claim is necessarily directed at the other treaty party, even if it is also directed at individuals that may enjoy rights or benefits under the treaty. Further, when the claim concerns the interpretation of a multilateral treaty but in the bilateral relationship with another state specifically, the addressee is that other state. For instance, in South China Sea, the Philippines expressed in Notes Verbales sent to China its positions as to its own and China’s entitlements in South China Sea pursuant to LOSC.
However, when a state makes a claim regarding the interpretation of a multilateral treaty without claiming a breach but does not indicate the claim’s addressee (either expressly or by context), the claim is directed at all treaty parties. Because silence in response to such claims may mean acceptance regarding the treaty’s interpretation,Footnote 67 more contextual circumstances are required, in order for opposition to be inferred from the silence of any of the other parties. As discussed below (Section 4.1.2.2), the claim must be clear as to the position of the claiming state and that the position of the addressee(s) departs from that of the claiming state.
4.1.2. The claim must be of ‘sufficient clarity’
Judicial decisions and state practice support that the claim must ‘refer to the subject-matter of the [rule being invoked] with sufficient clarity to enable the State against which [that] claim is made to identify that there is, or may be, a dispute with regard to that subject-matter’.Footnote 68 In Gambia v. Myanmar (2022), the ICJ called this requirement ‘sufficient particularity’.Footnote 69
The following conditions make the claim sufficiently clear:
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1. When a claim concerns a breach, it makes some factual allegation regarding the conduct of the addressee state;
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2. When the claim does not concern a breach, the claim articulates the position of the claiming state and how this differs from the position of the addressee state;
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3. The claim is sufficiently clear as to its subject-matter.
These are discussed in detail below. Because of these contextual conditions, the voting in favour or against a particular resolution or decision of an intergovernmental forum is insufficient to call for the reaction of another state, in the absence of which opposition can be inferred. Voting alone is unclear as to the position of a state, since resolutions frequently contain numerous exhortations and/or claims. A state that votes in favour or against a particular resolution may accept or disagree with only some of that resolution’s statements. However, a state’s statement in connection to its voting may be clear (about the aspects discussed below) and may thus establish a dispute in combination with a state that then remains silent.
4.1.2.1. When a claim concerns a breach, it must refer to the conduct of the addressee state
A claim alleging a breach of international law must articulate the conduct of the addressee state. However, a detailed factual allegation is not required. State practice before the ICJ and the ICJ’s reasoning about state silence and the existence of a dispute offer more support to this condition than LOSC state practice and jurisprudence.Footnote 70 For instance, in Hostages in Iran, the US had explicitly and repeatedly protested against the occupation and holding of hostages in the US Embassy in Tehran.Footnote 71 In Headquarters Agreement, the UN Secretary-General had repeatedly protested to US officials about the (future) adoption of the Anti-Terrorist Act and its inconsistency with the Headquarters Agreement.Footnote 72 In Georgia v. Russia, the Court found that there was a dispute based on Georgia’s claims, which clearly (albeit briefly) articulated Russia’s conduct.Footnote 73
In Marshall Islands, the Marshall Islands made a general criticism of the conduct of all nuclear-weapon states. However, because the statement did ‘not specify the conduct that gave rise to the alleged breach’, the Court reasoned that a reaction of India, UK or Pakistan was not called for, ‘given the statement’s very general content … ’.Footnote 74
In Gambia v. Myanmar, Gambia’s statements in the UNGA mentioned ‘terrible crimes’ and the ‘Rohingya issue’.Footnote 75 Although Myanmar argued that there was no dispute, because inter alia the claim must articulate the facts alleged,Footnote 76 the Court found that Gambia’s UNGA statements were sufficiently particular, because their context was the UN Fact-Finding Mission Reports that made factual allegations regarding Myanmar’s conduct.Footnote 77 Concerning Gambia’s Note Verbale in response to which Myanmar had been silent, the Court considered that the Note Verbale called for Myanmar’s response, because it referred to the findings of the Fact-Finding Mission, which described Myanmar’s conduct.Footnote 78
Finally, the factor that the claim mentions the conduct of the addressee state is separate from whether the claim is directed at the silent state. It is possible that a claim expressly identifies its addressee without articulating the conduct complained of. In this case, the claim is not sufficiently clear as discussed here. However, it is also possible that a claim does not explicitly indicate its addressee, but it is sufficiently clear about the conduct complained of and thus sufficiently provides the context for identifying the claim’s addressee (Section 4.1.1).
4.1.2.2. When the claim does not concern a breach, it must articulate how the claiming state’s position differs from that of the addressee state
As explained in Section 3.3, when a state makes claims about its own entitlements or a treaty’s interpretation, the silence of another state (party) may communicate acceptance of that claim. For opposition to be inferred instead, state practice and all decisions discussed in this study support the position that the claiming state’s understanding that there is a divergence of views must be articulated (unless the state’s views have been expressed earlier and are the context in which its silence is interpreted). This quality of the claim channels the meaning of state silence in response to that of opposition rather than acceptance.
4.1.2.3. The claim must be sufficiently clear about its subject-matter
International decisions consistently support that while the state making a claim does not need to make reference to a specific rule of law,Footnote 79 a claim that is vague as to its subject-matter cannot call for the reaction of another state, and a dispute cannot be inferred from that state’s silence.Footnote 80 That the claim must be sufficiently clear about its subject-matter concerns the content of a dispute,Footnote 81 and thus an ICT’s ratione materiae jurisdiction, which is often limited in compromissory or optional clauses.Footnote 82 But, since Marshall Islands, the ICJ’s reasoning supports that the requirement concerns the dispute’s existence.Footnote 83
However, the claim’s clarity as to its subject-matter is best understood as a requirement concerning the dispute’s existence, when assessing whether a dispute can be inferred from silence. Although no ICT has expressly stated this requirement for the inference of a dispute from silence, this requirement is supported by the principle of good faith.Footnote 84 A state should be expected to react when it is clear to an objective observer what is being claimed.
The reasoning behind this requirement is to caution the claim’s addressee and the claiming state that a dispute is being generated and to channel among different disputes: to help identify a dispute about a particular topic by virtue of the claim.Footnote 85
Let us assume that there is no ratione materiae limitation to a court’s jurisdiction, and the prospective applicant directs a claim at the prospective respondent, such as, ‘State A violates international law’. This claim is unable to convey the claimant’s position. The prospective respondent cannot understand the former’s position and cannot take a position on it. It is possible that State A agrees with the allegation depending on the claim’s subject-matter. For instance, State A may agree that it violates the right to property, while it may disagree that it commits ethnic cleansing.
Similarly, when claims do not concern a breach, a claim whose subject-matter is unclear, such as ‘I, State A, have rights in the North Sea’, does not call for the reaction of coastal or other states. Such a claim could be about any of the following various topics: innocent passage, freedom of navigation, sovereign rights, fishing rights, and so on and so forth. It is possible that a coastal state may agree, for instance, that State A enjoys freedom of navigation, but it may disagree that State A has sovereign rights over the continental shelf. Thus, some clarity about the claim’s subject-matter is necessary for a response to be called for and for a dispute to be inferred from silence.
Finally, to identify the claim, the text of the statement must be interpreted in its context (Section 4.1.3), in accordance with the rules of interpretation of unilateral declarations.Footnote 86 When a statement contains multiple express claims, international decisions support that all claims have been made.Footnote 87
4.1.3. The claim’s context
Statements and silence must be interpreted in their context in order to identify whether a dispute exists. Some examples of modern context that can be relevant when interpreting silence are the following.
4.1.3.1. Bilateral or multilateral settings
The context may be the bilateral exchanges between the parties.Footnote 88 Multilateral settings may also constitute the context of statements and silence in response. The subject-matter of an intergovernmental conference is part of the context in which the claim is interpreted and thus part of the context in which the silence in response to that claim is interpreted.Footnote 89
4.1.3.2. Other institutional processes
Expert treaty bodies (ETBs), such as the Human Rights Committee, have developed reporting processes. When the claims concern the breach by another state, and are made in the claiming state’s periodic reports to ETBs, they do not call for the reaction of the state at which the claims are directed. This is because normally periodic reporting concerns one’s own conduct; not another state’s conduct.Footnote 90
Further, the Reports of Fact-Finding Missions established by IOs may constitute the context for interpreting state claims. They can clarify the claim’s addressee and/or subject matter.Footnote 91
4.1.3.3. The claiming state’s status as a state other than the injured state does not undermine the claim’s clarity
The status of the claiming state, as a state other than the injured state, does not undermine the claim’s clarity for establishing the existence of a dispute. If the contrary reasoning were accepted,Footnote 92 only claims by injured states, namely only states specially affected by a breach of an erga omnes (partes) obligation, could call for the reaction of the allegedly responsible state. Yet, in some breaches of erga omnes (partes) obligations, there may be no specially affected state, such as when a state violates human rights against its own nationals. In such cases, the responsible state’s silence would shield it from the jurisdiction of an ICT, because no claim by any state could call for its reaction. Therefore, that the claim is made by a state other than the injured state does not weaken the claim’s clarity.
4.2. Awareness of another state’s claim
Judges and scholars have vehemently criticized the requirement that a claim’s addressee must be aware, or at least could not have been unaware of the claim, primarily on the ground that it introduces an unnecessary requirement of prior notice of the claim.Footnote 93 However, given that the response of the claim’s addressee cannot be anticipated – that state may expressly take a position or it may remain silent – the requirement of awareness ensures that if the response is silence, then silence can be interpreted as opposing the claim.Footnote 94
In Gambia v. Myanmar, Myanmar had argued that (i) the prospective respondent must be aware or at least could not have been unaware of the claimant’s position, and (ii) the claimant must be aware or at least could not have been unaware of the respondent’s position.Footnote 95 Gambia challenged the latter requirement,Footnote 96 because it would give a ‘silent veto’ to a prospective respondent.Footnote 97 The Court categorically rejected the ‘mutual awareness’ requirement. If the respondent was required to expressly oppose the applicant’s claims, ‘a respondent could prevent a finding that a dispute exists by remaining silent in the face of an applicant’s legal claims. Such a consequence would be unacceptable’.Footnote 98 Later, the Court reasoned that Myanmar’s rejection was inferred from its silence.Footnote 99 Thus, by rejecting the mutual awareness requirement, the Court has also rejected a proposition that it must be proven that the originally claiming state also understood that by being silent, the silent state rejected the original claim.
The awareness requirement comprises two alternative options: ‘actual awareness’ (‘be aware’) and ‘constructive awareness’ (‘could not have been unaware’).Footnote 100 The ICJ relies on the terms ‘awareness’ and ‘knowledge’ interchangeably.Footnote 101
Usually, a state becomes aware of a claim through direct communication (e.g., by Note Verbale).Footnote 102 However, when the claim is made (i) in an inter-state multilateral forum, (ii) through press releases or foreign media, or (iii) domestic media, constructive awareness becomes crucial.
4.2.1. Of claims in inter-state multilateral settings
Inter-state multilateral settings provide fora for public communication between states. They provide a setting where diplomatic tactics surrounding silence may take place. For instance, a state may abstain from a meeting, where it may be expected that a claim directed at it may be made by another state, precisely in order to avoid knowledge and thus to avoid the establishment of an ICT’s jurisdiction.
It is argued that constructive awareness is met when claims are made in permanent multilateral settings, because constructive awareness is the corollary of the effective functioning of permanent multilateral fora. A different approach is needed when assessing whether constructive awareness is met in ad hoc multilateral settings.
Permanent inter-governmental conferences, be they organs of IOs, such as the UNGA, or not, are composed of IO Members or all treaty parties respectively. They may have a multitude of competences, but they constitute permanent forums in which states exchange views. In practice, if states do not attend, bodies that administratively support the functioning of each conference or organ of the IO publicize the debates among all members.
International decisions support that awareness is met when claims are made in such fora. For instance, in Georgia v. Russia, Russia did not argue that it was not aware of Georgia’s statements in the UNGA or UNSC. The Court rejected the relevance of those statements for the existence of a dispute, but not on the ground that Russia lacked constructive knowledge of Georgia’s statements in these fora.Footnote 103 In Gambia v. Myanmar, the ICJ reasoned that Myanmar could not have been unaware of Gambia’s allegations in the UNGA general debate.Footnote 104 Similarly, in South Africa v. Israel, it noted that ‘Israel was represented’ at the UNGA extraordinary meeting, where South Africa alleged that ‘the events … in Gaza have illustrated that Israel is acting contrary to its obligations [under] the Genocide Convention’.Footnote 105
Presence in such a meeting can be evidence of actual awareness of a claim made therein. Separately, there is no state practice and no international decisions that support and explain the reasoning behind the proposition that constructive knowledge is met when a claim is made in a permanent multilateral forum. It is argued here that, when a state is present and even if it is absent during a meeting when a statement is directed at it, constructive awareness is met, because constructive awareness is the corollary of the effective functioning of these conferences. For instance, the UN Members intended the UNGA to function effectively to achieve the objectives for which it was instituted,Footnote 106 including the efficient communication between states. Further, from a policy perspective, this reasoning ensures that states are not encouraged to not be present in the UNGA in order to avoid having awareness.
On the other hand, ad hoc conferences are convened by IOs or by governments on a particular subject-matter. States, which have not been invited and states that have been invited but do not attend, cannot have constructive knowledge of claims made in an ad hoc conference based on the reasoning applicable to permanent inter-state fora.
In Marshall Islands, the Marshall Islands had made a statement at an ad hoc Conference on the humanitarian impact of nuclear weapons. India and Pakistan were present. The UK objected that it did not participate, and that the Marshall Islands did not notify it of this statement.Footnote 107 The Court noted that the UK was not present,Footnote 108 but drew no particular consequence from this fact. In all three judgments, which have identical reasoning, the Court reasoned that the content and context of the statement were not such as to raise the expectation of response.Footnote 109 The Court’s decision thus provides no evidence as to whether constructive awareness was or not met (for the UK in this case).
Three normative arguments can be made in favour of constructive awareness when a state is not present at an ad hoc conference. The third is persuasive.
First, Judge Sebutinde, in her Separate Opinion, in Marshall Islands v. UK, argued that the UK’s specific stance to all negotiations of nuclear-disarmament was the background against which the UK’s absence can be understood as a tactic so as to avoid awareness.Footnote 110 She argued that, in these narrow circumstances, constructive knowledge must be met. Although compelling, this argument depends on whether there is evidence that the state’s absence is a tactical choice. It does not support generally that constructive awareness is met where a state is not present at an ad hoc conference.
Second, in his dissenting opinion, in Marshall Islands v. UK, Judge Robinson argued that in the modern world of communications technology, it is reasonable that the statement of the Marshall Islands in the Nayarit Conference would not have escaped the UK’s attention.Footnote 111 However, if, as Judge Robinson suggests, states are expected to know any statement made against them in any ad hoc conference that they have not attended, all states would be burdened significantly, and developing countries would be burdened unreasonably.
Third, building on, but departing from, Judge Robinson’s argument, it could be argued that states that have particular interests in a field, such as those that hold nuclear weapons, cannot be unaware of claims against them in ad hoc conferences that concern those particular interests, even if they do not attend, assuming that these statements are public through modern communications media. This approach, which is compatible by analogy with existing jurisprudence about acquiescence,Footnote 112 would represent reality better, thus not burdening states unreasonably, when they do not have particular interest in a field.
4.2.2. Of claims in press releases and global or regional media
State representatives regularly make statements through mass or social media, which have foreign or global reach. Ministries of Foreign Affairs also often make press releases, including on their websites. Yet, statements in the media do not guarantee receipt and thus actual awareness of the statement. Their principal purpose is not to bring a state’s views to the attention of the claim’s addressee, but to raise the awareness of the wider public – domestic, regional and worldwide – about a state’s views, thus gaining political support or undermining the reputation of the state at which the claim is directed.
Some support in case law exists in favour of the position that actual awareness of claims made in global or regional media can be met. For instance, in Georgia v. Russia, the ICJ found that a dispute existed between Georgia and Russia based on statements of Russian representatives,Footnote 113 which proved that they had actual knowledge of Georgia’s in press briefings or statements in media of global or regional reach.Footnote 114
State practice offers minimal support that constructive knowledge would be met in such instances. For instance, in relation to the BBC interview by Georgia’s President-elect, the Court, in Georgia v. Russia, considered that the context and content of the statements in that interview did not call for Russia’s reaction. However, the Court’s reasoning was not that Russia lacked constructive knowledge of those statements.Footnote 115
Further, Georgia had argued that statements of Georgia’s President ‘in a press conference with foreign journalists’, in his ‘CNN interview’ as well as the press briefing of Georgia’s Ministry of Foreign Affairs made claims that were opposable to Russia.Footnote 116 It also pointed out that Georgia’s President-elect had made allegations about ethnic cleansing in a 2004 interview in BBC, which was broadcasted in Russia.Footnote 117 For Georgia, Russia had constructive knowledge of Georgia’s claims.
Russia did not argue that it did not have constructive knowledge of CNN interviews, press releases or interviews in regional broadcasters,Footnote 118 but expressly argued that statements made in Georgian media were not opposable to it.Footnote 119 It can be extrapolated that Russia accepted that it had constructive awareness of claims in press releases or through global or regional media.
Although state practice and jurisprudence do not support sufficiently that constructive knowledge would be met for statements made in global media, it could be argued that, depending on the particular interests that a state has in a particular field or in a relationship with another state, constructive knowledge would be met, given the widespread publication of such statements. This reasoning would be compatible, by analogy, with existing jurisprudence.Footnote 120 It would also reflect better the reality of states’ capacity.
4.2.3. Statements addressed to domestic audience
In practice, state officials make statements addressed entirely to their state’s domestic audience but conveying claims directed against another state. Such statements can be, and often are, made in domestic political party conferences or through domestic newspapers or media. Such statements may be intended to maximize domestic political benefits or minimize domestic political costs. However, it is argued here that, despite the domestic political motivations behind them, claims made to domestic audience can constitute evidence of the existence of a dispute with another state. On the one hand, states are likely to know statements of other states made in a domestic context. In reality, domestic media, especially of neighbouring states, will reproduce such statements, and ministries of foreign affairs have dedicated departments on particular topics or on relations with particular states. On the other hand, states should be expected to behave diligently, including when they make claims about other states or about their relationship with other states, irrespective of which audience they address. As a result, when the claim’s addressee responds by rejecting the claim made against it, even if that original claim has been made exclusively to a domestic audience, a dispute is established. But, when the claim’s addressee remains silent, a dispute can be established, if claim’s addressee does not deny that it actually knew the claim.
However, when the claim’s addressee denies actual awareness, constructive awareness becomes pertinent. There is no express support, in state practice or international decisions, that states have constructive awareness of other states’ statements made in the latters’ domestic media. For instance, in Georgia v. Russia, among the evidence that it submitted, Georgia included interviews of its officials in Georgian media.Footnote 121 Russia argued that: ‘it must be for Georgia to … communicate a claim, not for Russia to go out to seek it by watching Georgian television’.Footnote 122 The Court did not address this issue.
It might be argued that the ICJ’s reasoning, in Nicaragua v. Colombia, implies that a state has constructive knowledge of claims made by another state to the latter’s domestic audience. The facts of this case did not concern silence and the Court did not deal with the inference of a dispute from silence. However, it might arguably be relied on by analogy. In determining whether a dispute existed, the Court reasoned that ‘Colombia could not have misunderstood’ Nicaragua’s positionFootnote 123 in a statement that Nicaragua’s President had made in an event of the Nicaraguan Sandinista Youth organization,Footnote 124 without evidence that this statement was notified to Colombia. The constructive knowledge envisaged by the Court here was about Colombia’s knowledge of Nicaragua’s response to Colombia’s original publicly made claim.
However, the reasoning of constructive awareness, when assessing the legal meaning of state silence, is to ensure that the silent state is expected to respond in the absence of which a dispute will be established. Instead, awareness of the response rejecting one’s original claim (i.e., mutual awareness), which is what the Court was concerned with in Nicaragua v. Colombia, is about knowledge that a dispute has been established. Given this distinction, it could be argued that a lower constructive knowledge threshold might be justified for the latter ‘leg’ of knowledge, but not in relation to the expectation to react to an original claim. In any event, the Court has since categorically rejected the latter requirement in Gambia v. Myanmar (Section 4.2), and this weakens the strength of an analogy with its reasoning here.
Further, an analogy with the reasoning, in Fisheries,Footnote 125 is inapposite. In that case, Britain tolerated Norway’s legislation, which was adopted and enforced for 60 years, not an instantaneous statement in a domestic audience. Additionally, subsequent judicial reasoning supports that states are not expected to know other states’ domestic law.Footnote 126 If states are not expected to know the domestic legal developments in another state, a fortiori they cannot be expected to know statements made purely domestically.
The reasoning that is more harmonious with existing jurisprudence is that, as a default, states are not expected to know claims against them which have been made in an entirely domestic context of the claiming state. However, the relationship between the two states and the significance of the subject-matter in their relationship, as well as their previous exchanges about it, may contribute to constructive knowledge. Separately, if a state actually knows of claims that the claiming state made in its own domestic audience, actual awareness is met and a dispute can be established (by statement or silence in response).
4.3. The silent state is ‘in a position’ to respond
When a silent state is deprived of ‘a fully operational government and administration’, such as when a state is afflicted by civil war or international armed conflict,Footnote 127 some ICTs have refused to infer acquiescence. There is no state practice or international decision that has considered that a dispute cannot be established when the silent state is experiencing the aforementioned circumstances. However, the reasoning behind the aforementioned proposition is that a state’s will should be taken to be manifested when the state is reasonably capable to manifest its will. Thus, to the extent that the inference of a dispute from silence relies on an inference of rejection from silence, as the Court has reasoned in Gambia v. Myanmar, the same reasoning should apply to the inference of opposition from silence.
A concern arises when the claim directed at the silent state concerns the very situation in which the silent state is involved thus causing its ‘incapability’. For instance, if a state being involved in an armed conflict is taken not to be in a position to react during that time, it could prevent the establishment of a dispute about the lawfulness of its own use of force from being established merely by remaining silent. It could be argued that in such situations, a dispute can be established by virtue of that state’s silence. In such case, the silent state’s situation may be a factor for assessing the reasonable time of silence (Section 5).
In any event, when a state is thematically silent (it uses non-responsive speech), the assumption should be made that it is in a position to respond.
5. Reasonable time of silence
For silence in response to another state’s claim to mean opposition, silence must be held for a reasonable time. Although the first decision to rely expressly on reasonable time of silence for inferring rejection from that silence was Gambia v. Myanmar (Preliminary Objections) (2022), scholars, already in the previous century, had supported this requirement.Footnote 128
Under general international law, there is no fixed time of silence for establishing a ‘dispute’, in the same way that there is no fixed time for establishing other legal situations, such as acquiescence, prescription or estoppel.Footnote 129 What is reasonable time of silence depends on the circumstances of each case. Various factors can be relevant.
For instance, in Gambia v. Myanmar, in its pleadings, Gambia relied on the claim’s nature and gravity, and the silent state’s (Myanmar’s) actual knowledge.Footnote 130 The Court did not accept that one month of silence, in and of itself, and in general, is reasonable. It considered: (i) ‘the nature and gravity of the allegations’, and (ii) that Myanmar had ‘knowledge of the allegations’ prior to receiving the Note Verbale.Footnote 131 Further, the Court did not consider that the two circumstances constitute a mandatory minimum threshold. The Court merely relied on the circumstances of the particular case.
The Court did not explain the meaning of the ‘nature and gravity of the allegation’. These are two different concepts, and are subject to multiple interpretations. Owing to the case’s facts, the Court’s reasoning entails that short periods of silence are reasonable vis-à-vis allegations of breach of erga omnes (partes) obligations, and by implication of the smaller groups of erga omnes obligations which constitute jus cogens. However, a wider conclusion that longer time would be required, if a breach of bilateral obligations were alleged, is incorrect. The context, facts and circumstances of the case must be considered as a whole. For instance, where the claim alleges a breach of bilateral(isable) obligations, which significantly affect vulnerable populations, a one-month period of silence may be reasonable. An example is when the silent state is accused of restricting innocent passage, which is a lifeline for imports of products of subsistence of civilian population. Here, the interests at stake may be of great importance, despite the fact that the obligation allegedly breached is not erga omnes (partes).
Further, by analogy, some state practice before and decisions of ICTs as well as scholarship about acquiescence support that other factors may be relevant for assessing whether the time of silence is reasonable for inferring a dispute. For instance, Kolb argues that the frequency of the conduct to be opposed, the legal relationship in question, the importance of interests at stake, the intensity of the parties’ relationship, and whether knowledge of the claim is actual or constructive, may shorten or elongate the reasonable time of silence for establishing acquiescence.Footnote 132 Additionally, in Temple Preah Vihear, Cambodia argued that the claim’s subject-matter (such as, territorial boundaries claims) may require a shorter period of silence for establishing acquiescence; as does conduct that is dense and frequent.Footnote 133 For the Court, two years of silence vis-à-vis a territorial boundary claim established acquiescence.Footnote 134
Shorter time of silence may be reasonable for inferring a dispute from silence than establishing acquiescence.Footnote 135 This can be explained by the reasoning behind attributing each legal meaning to silence. On the one hand, state consent and its equivalent, namely acquiescence, cannot be easily presumed. On the other hand, shorter periods of silence are reasonable for inferring a dispute, than those expected for acquiescence, because the inference aims to ensure that international adjudication is not unilaterally undermined by a silent state.
6. ‘Other reasonable explanations’ for silence do not preclude the inference of a dispute
In Ecuador v. US, the Tribunal reasoned that the ‘inference of “positive opposition” is warranted only when all other reasonable interpretations of the respondent’s conduct and surrounding facts can be excluded’.Footnote 136 This reasoning led the Tribunal to find that because the US had a reasonable alternative motivation behind its silence, the circumstances did not warrant the inference of ‘positive opposition’.Footnote 137
The Tribunal’s reasoning should not be adopted. First, there is no support in the prior decisions relied on by the Tribunal,Footnote 138 or subsequent decisions (Table 1). There is also no state practice. Second, although it could be argued that Ecuador v. US is consistent with the reasoning that ‘proof may be drawn from inferences of fact, provided that they leave no room for reasonable doubt’,Footnote 139 ‘a less exacting standard of proof’ than that of ‘high level of certainty’ applies in some cases.Footnote 140 The inference of a dispute from silence should be one of these cases for the following reasons. The Ecuador v. US reasoning would make it impossible to infer opposition from silence, because alternative reasonable explanations can be provided for silence even when all factors discussed in this study are present. This is partly because multiple motivations may exist behind silence. For instance, in Georgia v. Russia, one reasonable explanation for the (thematic) silence of Russia’s MFA would be that the US had requested both Georgia and Russia to tone down their ‘narratives’ and Russia was doing so, while pointing out that Georgia was not. This does not mean that it did not also oppose Georgia’s claims. Additionally, the reasoning, in Ecuador v. US, is premised on the assumption that what matters is the true will of the silent state. However, even when interpreting statements, what matters is not what a state truly believes, but what it ‘says’. Similarly, what matters is silence’s communicative content: whether in light of the circumstances surrounding it, silence can reasonably communicate a view. Finally, allowing a state to argue subsequently that did not truly oppose would undermine legal certainty.
7. Conclusions
State silence appears in its prototypical complete form less often than when silence is conjoined with various instances of speech or action. In the latter scenarios, states seem to perceive statements and conduct other than silence as stronger evidence of a dispute. The way states plead ‘silence’ depends on each case’s facts. However, only in two instances have states argued that a dispute exists entirely based on a prospective respondent’s silence: Ecuador, in Ecuador v. US; and Panama, in Norstar. In all other 11 cases,Footnote 141 states provided as evidence of a dispute not only the (prospective) respondent’s silence, but also the respondent’s other conduct–linguistic or non-linguistic.Footnote 142 Further, as shown in Table 1, ICTs have found a dispute, exclusively based on silence, only exceptionally, in only two decisions: Hostages in Iran and Norstar. In contrast, in one decision, Ecuador v. US, the tribunal found no dispute where the applicant relied exclusively on the respondent’s silence;Footnote 143 and, in three decisions, Marshall Islands, the ICJ found that no opposition of views can be inferred from the absence of any reaction.
Where the facts involve silence and speech, silence remains a relevant factor–expressly mentioned–in ICTs’ assessments. In four other decisions, ICTs relied on the respondent’s statements and silence to establish a dispute (Table 1), arguably as a supplementary evidence of a dispute’s existence.Footnote 144 Further, in five decisions, silence did not vitiate the dispute’s existence, which was found to have been established by way of actions or speech (Table 1).
This study has argued that when assessing whether a dispute can be inferred from silence, the following circumstances must exist: a claim has been made in circumstances that call for the silent state’s reaction; the silent state is aware of the claim; and reasonable time of silence passed. All these conditions apply to silence in response to claims made in bilateral or multilateral contexts, to claims that concern bilateral relations or obligations that protect community interests, to claims communicated diplomatically or through the media, and to jurisdiction based on compromissory clauses or unilateral consent.
While these conditions appear to be identical to those that apply when assessing whether acquiescence can be inferred from silence, there is a material distinction. For opposition to be inferred from silence, the claiming state (i) either alleges that the other state (that then remained silent) violated international law or (ii) it claims rights for itself and articulates the diverging position of the silent state. Instead, for acquiescence to be inferred from silence, the claiming state claims that its own conduct is lawful or that itself has entitlements or obligations (Section 3.3.).
The inference of opposition and the conditions, under which it can be made in order to establish the jurisdiction of an ICT, face two camps of critics relatively represented in the two schools of thought about the function of international adjudication. On the one hand, those favouring voluntarism, the idea that the adjudication’s goal is to resolve disputes, and a less litigious legal order argue that the inference and its conditions ignore state consent, prioritize litigation over other alternative means of settlement, and even encourage disputes. For them, the inference should not be made or should be made only in the exceptional circumstance where no other reasonable explanation can be furnished for a state’s silence.
On the other hand, those favouring adjudication argue that the conditions reflect unnecessary formalism hampering access to justice,Footnote 145 and undermining the international rule of law. For them, there is no need to rely on an inference of a dispute from silence. At least in relation to claims that concern breaches of international law, a mere complaint against another state’s conduct suffices to establish a dispute. As it has been explained (Section 3.3.), the counter-argument has been made that this approach should not be adopted because it entails that the position of only one state creates a dispute. Case law is consistent that the opposing views of two states establish a dispute.
Judge Abraham has argued that a presumption could be made that a state always believes that its conduct is lawful.Footnote 146 A dispute would be established immediately once a complaint was made, because two claims (one based on a presumption) would oppose. There would be no need to infer a dispute from silence in response to the complaint. However, to date, ICTs have not adopted this approach in relation to assessing whether a dispute exists, and states have not yet made such an argument in their pleadings. Additionally, some caution is called for because a general presumption that a state always believes that its conduct is lawful may have wide-ranging implications. For instance, a state breaching international law would be presumed generally to make a claim (simply by virtue of its breach) that it acts lawfully. Such a claim would call for the reaction of other states and may lead to law evolution.Footnote 147 Further, the concepts of (silent) ex post facto waiver of a claim or acquiescence to the lapse of a claim concerning another state’s responsibility might lose their relevance: the initial (presumed) claim of lawfulness coupled with silence in response would entail ab initio consent.
For as long as the approach that relies on the reaction of the prospective respondent is followed for inferring a dispute, and the facts involve the latter’s silence and unchanged conduct, the inference of a dispute from silence and the conditions under which the inference can be made ‘speak to’ both the aforementioned rival criticisms. On the one hand, because it prevents tactical silences intended to undermine international justice, the inference must be encouraged. On the other hand, the context in which silence can be interpreted to mean opposition performs an evidentiary function and enables the dispute’s establishment despite a state’s abstention from expressing a view. These contextual factors or conditions are thus a matter of substance, not of form. They are also compatible with the reasoning that only opposing claims (manifestations of will) of the parties in question can establish a dispute’s existence.Footnote 148 They thus address the concerns about undermining voluntarism. Further, the conditions serve subsidiary functions. A claiming state is being cautioned that, by making claims of particular quality, it generates a legal process, and a particular legal process–a ‘dispute’, as opposed to any other legal process, such as acquiescence in international law-making. Similarly, the claim’s addressee is being cautioned that a legal process and a particular legal process is being generated, which can crystalize into a dispute, even by its silent response. For these reasons, the conditions for inferring a dispute from silence should be retained in international adjudication.
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