Judicial Reasoning and Non-State Participation before Inter-State Courts and Tribunals

In: The Law & Practice of International Courts and Tribunals
Brian McGarry Assistant Professor, Grotius Centre for International Legal Studies, Leiden Law School Leiden The Netherlands

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Yusra Suedi Fellow in Law, London School of Economics and Political Science, University of London London UK

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Open Access


The present article explores the premise that the participation of non-State actors may in some instances be necessary to the conduct of contentious or advisory proceedings before inter-State courts and tribunals. It first considers whether such necessity may be directly asserted as a legal requirement, in the absence of lex specialis treaty mechanisms or party consent. The article thus considers the potential to apply general principles of law, customary international law, and doctrinal concepts to this question. Unsatisfied with reliance on the stated legal considerations of international courts and tribunals, however, it turns to assess the root causes of such necessity, beneath pronouncements of legal sources and doctrine. The authors identify these as practicality – which speaks to what a court or tribunal must do to fulfil its mandate today – and legitimacy, which speaks to what it should do to ensure that its mandate is respected tomorrow.

1 Introduction

While non-State actors (NSA s) have enjoyed greater participation in international dispute settlement proceedings since the turn of the millennium,1 their contributions to inter-State proceedings remain limited in practice. In this light, the present article explores the provocative notion that an inter-State court or tribunal may in some instances consider such participation necessary to the conduct of its proceedings.2 This article lifts the veil of judicial reasoning in order to assess the root causes of such necessity, beneath pronouncements of legal sources and doctrine. It applies this lens of necessity to both contentious and advisory proceedings, and thus endorses the overlapping of these types of proceedings in recent practice.3 While the scope of the article is limited to NSA s such as individuals, corporations, and non-governmental organisations, it draws comparisons to the non-party participation of States and intergovernmental organisations where relevant. The authors do not focus exclusively on amicus curiae or any other particular form of NSA participation, but rather consider a range of scenarios in which NSA s may seek to address an international court or tribunal without the direct support of a party to the proceedings.

This article first considers the application of legal sources to the question of NSA participation, in order to determine whether the necessity of such participation may be directly asserted as a legal requirement (2). It assesses the formal sources of international law reflected in Article 38(1)(a)–(c) of the Statute of the International Court of Justice (ICJ, or the Court), as well as doctrinal concepts which do not neatly fit within those provisions (“informal” sources of international law).4 Unsatisfied with reliance on the stated legal considerations of international courts and tribunals, the authors identify distinct types of situations in which NSA participation has been (or may be) accepted in inter-State proceedings (3). Having characterised the underlying rationales of NSA participation as practicality and legitimacy, we look ahead to the future (4).

2 NSA Participation Viewed as a Legal Necessity

A logical starting point for this inquiry is to determine whether any sources of law compel international courts and tribunals to include NSA s in proceedings, thereby rendering such participation legally necessary. Inter-State courts and tribunals fulfil mandates to resolve disputes by applying legal sources recognised by States. An abundance of applicable sources will require the judge or arbitrator to balance and account for different rules and principles.

These sources can include the instrument of jurisdiction and the constitutive statute of an international court. While disputing parties cannot mutually agree to modify the supervening provisions of the ICJ Statute,5 a compromis or compromissory clause empowering the participation of NSA s in judicial proceedings would not clearly contravene any express provision of the Statute (and would directly govern these questions for ad hoc inter-State tribunals). Yet there is a dearth of inter-State judicial settlement treaties which expressly provide for NSA participation.6 Therefore, the present article does not dwell on existing treaty sources for NSA participation, nor the comparatively narrow range of interpretative questions which arise for courts and tribunals when applying expressly conferred powers.7 Nor do the authors explore references to NSA participation in the procedural rules adopted by international courts and tribunals, as such rules merely implement mandates found in treaties (and cannot themselves directly confer judicial powers).8

At root, this analysis thus relies upon the uncodified sources of international law discussed herein, rather than the black letter of judge-made rules. In this section, we assess whether the sources formally recognised in Article 38(1)(a)–(c) of the ICJ Statute – and doctrinal concepts which do not neatly fit within those provisions (“informal” sources of international law) – can render NSA participation legally “necessary” in such proceedings. If such sources impose requirements binding upon the parties in respect of their dispute, a properly seized court or tribunal must take these into account when administering the proceedings. A theoretical consequence of departing from such requirements is the legal invalidity of the decision.

The concept of nullity or voidness is recognised in the law of treaties in a number of instances, notably in regards to the contravention of jus cogens.9 In the context of international judgments and awards (rather than treaties), some scholars have taken a purely objectivist view of nullity, such as Schlosser’s observation that “an award may be null and void ab initio without any claim alleging the nullity having been formally presented”.10 In practice, nullity may also be framed in terms of the scope of State consent. For example, when the United States refused for 50 years to implement the award in the Chamizal arbitration with Mexico, the stated reason was that the arbitrators had exceeded their authority under the compromis.11

Historically, most instances of non-execution of an international award were paired with allegations of nullity.12 Perhaps uncoincidentally, nullity was notably absent from early codification efforts in international dispute settlement. At the 1899 Hague Conference, the delegates considered it undesirable to specify causes of nullity, and preferred to leave this to the discretion of the reviewing judge in future cases. The Conference, deeming it impracticable to propose a procedure for adjudicating allegations of nullity, ultimately said nothing about the substantive law of nullity.13

The International Law Commission’s (ILC) 1958 Model Rules on Arbitral Procedure attempted to codify enumerated bases for the invalidity of an award. The ILC included among these the reason of “a serious departure from a fundamental rule of procedure”.14 Two years later, the ICJ in King of Spain sketched certain formal requirements for the legality of an international decision. Upholding the underlying award’s validity, the Court noted “that it deals in logical order and in some detail with all relevant considerations and that it contains ample reasoning and explanations in support of the conclusions arrived at by the arbitrator”.15 This appeared to support the views of Carlston and Cheng, who had found that a deprivation of the opportunity to present proofs or arguments to the tribunal would give rise to nullity.16

In light of the possibility of nullity arising from the conduct of cases, we may apply this lens to NSA participation in inter-State cases. Instances of “intrinsic difficulties” – where information from NSA s may be necessary for a court’s reasoning – may frame NSA participation as a means to avoid certain identified grounds for nullity, including lack of a motivated judgment, uncertainty and ambiguity, and essential error.17

This is illustrated in diplomatic protection claims – as well as proceedings before inter-State claims commissions – in which the potential for legally ineffective adjudication is seen in instances where the court or tribunal has been underinformed, or misinformed, by the parties. A case may raise questions as to the respondent’s treatment of nationals of the applicant State.18 Nationality questions may thus arise in this context as well.19 In the Lizardi case, between the United States and Mexico, questions arose as to whether the tribunal had been deceived under oath concerning the citizenship status of the case’s namesake.20 As a nationality link between the individual and the State is a requirement for the admissibility of such claims,21 the individual’s participation may not only serve the respondent’s interest in examining the witness – it may provide an essential basis for the court or tribunal to determine whether it can exercise its jurisdiction.22

A further question arises as to whether the Court, if seized with a case that it considers it cannot fairly or effectively resolve without NSA participation, may decline to render a decision. This prospect was first raised in the context of advisory proceedings. In Eastern Carelia, the Permanent Court of International Justice (PCIJ) declined to render an opinion following the refusal of the USSR, a non-Member of the League, to participate in the proceedings and provide critical information.23

2.1 Formal Sources of International Law

In this light, we explore whether the sources formally recognised in Article 38 of the ICJ Statute can render NSA participation legally “necessary” in contentious or advisory proceedings. We first assess the potential role of general principles of law in this regard, before turning to briefly consider the application of customary international law.

2.1.1 General Principles of Law

We first ask whether there are general principles which compel NSA access to proceedings between States. General principles of law were envisaged (and are practiced) under Article 38(1)(c) largely as “gap-fillers” for lacunae in the normative content of international law. Lauterpacht considered that this was essential to the international judiciary’s role in ensuring the completeness of international law – in his view, an a priori principle of the international legal system.24 Such a view naturally tends to welcome more inclusive participation in international adjudication, and in particular an ebbing from the traditional exclusion of NSA s from inter-State legal proceedings (e.g., contentious cases before the ICJ).25

As reflections of municipal law, the greatest contribution of general principles to the practice of international courts may be in regards to the treatment of the individual. Meron observes that while such principles are particularly evident in the practice of ad hoc international criminal tribunals, they may also have broader potential “for the emergent international law concerned with the individuals, business companies, environmental dangers and shared resources”26 – all of which subject-matter arises before inter-State courts and tribunals today.

As a key requirement of the rule of law, a formal right of access to courts for the resolution of disputes finds expression as a general principle.27 Inter-State courts such as the World Trade Organization (WTO) Appellate Body have acknowledged an obligation to treat interested parties according to terms of equality, as a general principle of law cognisable at both the domestic and international levels.28 Supranational inter-State courts such as the Court of Justice of the EU have identified a general principle of effective judicial protection in administrative proceedings.29 In so doing, such courts with substantial law-making authority recognise that this principle may equally govern their own proceedings.30

Due process is a particularly relevant general principle in legal proceedings. While general principles partly consist of broad rules regulating the conduct of both private parties and States in various contexts (such as the principle of good faith), they also consist of rules governing the process in domestic or international proceedings.31 The latter set of general principles are said to “represent the core concept of international due process”.32

Due process is understood to denote certain minimum procedural standards necessary to guarantee fairness in judicial proceedings.33 Several of these standards have been widely accepted in international law, such as the right to be heard and the equality of parties. They have often been invoked and exercised before human rights courts and tribunals, and connected to the right of access to justice.34 When a request for an opinion directly concerns the rights of NSA s, Brownlie considered that “the Court must, in order to do justice effectively, provide them with the opportunity to submit their views whether or not they are parties as a matter of procedure”, and concluded that “[t]o give the opinion without hearing them would be violating the principle of audiatur et altera pars [may the other side also be heard]”.35

Nevertheless, due process may be more easily understood in relation to the rights of parties to proceedings, as opposed to the rights of other participants. Those who view general principles of law as firmly rooted in municipal practice are moreover likely to reject the universality of any principle tailored to amicus curiae or other forms of NSA participation, as such practices are most readily available in common law domestic systems. Scholars who define general principles of law principally in terms of their abstraction – as opposed to more specific and prescriptive rules of customary international law – will similarly conclude that there can be no general principle of law concerning amicus curiae participation before international courts.36

Certain general principles may even be viewed as limiting the role of individual participation in inter-State proceedings. In particular, principles of party autonomy such as ne ultra petita prohibit a court from exceeding the scope of the dispute submitted by the parties.37 This may, in turn, caution an inter-State court against accepting submissions from civil society or individuals when such submissions go beyond questions raised by the parties.

Looking beyond due process, certain evidentiary principles have been applied by inter-State bodies, such as concern the burden of proof. Yet none of these principles beckon NSA s to provide evidence.38 It is thus difficult to identify a general principle that clearly compels NSA access to proceedings between States.

2.1.2 Customary International Law

Turning to Article 38(1)(b) of the ICJ Statute, we note that customary international law is limber enough to acquire emerging rules of practice and, in so doing, hasten their universal acceptance.39 Weil maintained the conservative argument that States exclusively create and apply rules of international law, but nonetheless accepted increasing participation of individuals under international law on the basis that such rights arise through (State-made) customary international law.40 Jennings and Watts acknowledged a limited international personality for individuals, arising from their direct international rights and duties.41 Yet contemporary scholars have disagreed as to whether an emerging rule of customary international law might support specific forms of NSA participation, such as the submission of amicus curiae briefs.42

Among “ordinary” rules of customary international law, there does not appear to be clear support for an inter-State court or tribunal’s authorisation of NSA participation on grounds of legal necessity. It may be worth considering, however, whether any jus cogens norms may be applicable in this situation.43 The participation of NSA s in inter-State judicial proceedings may be justified as legally necessary if due process is viewed as a jus cogens norm of broader application than “ordinary” rules of custom and general principles.

The jus cogens character of due process finds some support in the practice of human rights conventions. For example, States cannot make a general reservation to the right to a fair trial under Article 14 of the International Covenant on Civil and Political Rights.44 While the widely accepted jus cogens norms are usually the likes of genocide, torture or slavery,45 the Fourth Report of the Special Rapporteur of the ILC states that the jus cogens status of due process enjoys a degree of support.46 Due process has also explicitly been described as enjoying jus cogens status in certain domestic judgments.47

If due process were viewed as a jus cogens norm, this would raise the question as to whether an inter-State court or tribunal risks violating a jus cogens norm of due process by refusing the participation of NSA s in a given case. Yet it is dubious whether there is enough international support and recognition of due process as a jus cogens norm. Even if adequate recognition existed, its application in the context of non-party participation is highly questionable. As discussed above in the context of general principles of law, it is particularly difficult to see how an NSA might enjoy any per se right of due process in inter-State proceedings, without an underlying lex specialis access mechanism in the court’s constitutive treaty.48 The aforementioned limiting principles of party autonomy, such as ne ultra petita, may raise further doubts when defining a peremptory norm of due process so broadly.

2.2 Informal Legal Sources

Beyond the formal sources of international law, we may query whether certain informal sources may provide a basis for enlarging participation before an international court or tribunal. These include the application of generic judicial doctrines (e.g., the sound administration of justice), and the assertion of specific powers which are not expressly conferred by the constitutive treaty of that body (e.g., inherent or implied powers). We consider these in turn, recalling the somewhat cryptic view of the PCIJ Statute’s drafters, who unanimously considered its access limitations were “without prejudice to any subsequent development” of the Permanent Court.49

2.2.1 The Sound Administration of Justice

The doctrine of the sound administration of justice (also commonly referred to as the “proper” or “good” administration of justice) is an overarching norm in the proceedings of inter-State courts and tribunals. This doctrine empowers a judicial body with a large breadth of discretion to make the necessary adjustments to carry out its procedural functions in the most optimal conditions. It originated in the concept of denial of justice,50 which was developed in the Middle Ages to advocate for the rights of individuals to justice.51 The doctrine thus evolved to describe the antithesis of the denial of justice for individuals.52 It is commonly understood to include considerations of due process and the equality of parties,53 and the ICJ has linked it to notions of procedural fairness.54 While no formal definition exists under international law,55 Kolb has identified objectives to which this doctrine is applied, such as “to find the best possible equilibrium with regard to justice and procedural necessities”.56

This doctrine continues to be raised in the ICJ’s contentious cases,57 as well as in its advisory practice. Prior to June 2016, the ICJ occasionally dealt with distinct types of cases centring on international civil servants who were not satisfied with the decisions rendered by an administrative tribunal dealing with their matters. The United Nations Administrative Tribunal (UNAT)58 until 199559 and the Administrative Tribunal of the International Labour Organization (ILOAT)60 until 2016 were able to have these decisions re-examined by the Court. This type of advisory proceeding before the Court was abolished, however, chiefly due to the latter’s inability to satisfactorily adjust its procedural mechanisms in a way that fully respected the principle of the equality of parties – and its two constituent elements, equality of access and equality of arms – in favour of the civil servants involved.61

This equality of access was problematic with regard to the ILOAT as, while the UNAT allowed both the wronged staff member and the international organisation to seize the Court,62 Article XII of the ILOAT Statute only allowed the international organisation to do so.63 But even if this clause were to be amended, the international civil servant would still have not enjoyed access to the Court under Article 66(2) of the ICJ Statute, which does not explicitly invite individuals to provide written or oral information in advisory proceedings – nor Article 34(1), which limits judicial standing to States in contentious cases.

Still considering that the participation of the injured staff members was necessary in such proceedings, the Court tried to compensate for this inequality of access by adapting the equality of arms in two ways. First, an actor with access to the Court in advisory proceedings (such as an international organisation, or the Secretary-General) would arrange to transmit the views of the concerned staff members to the Court.64 Second, oral hearings were removed altogether to reduce inequality in the proceedings.65

It was finally decided to abolish the option of seizing the Court for such matters. Despite its efforts to close the inequality gap between the parties, the Court considered that its Statute inhibited it from sufficiently involving the necessary NSA s. This example illustrates how inter-State courts have at times considered the participation of NSA s to be necessary to achieve the sound administration of justice.

2.2.2 Inherent or Implied Judicial Powers

The concepts of inherent and implied powers concern, respectively, the court or tribunal’s power to take measures necessary to ensure that proceedings conform with fundamental rules of procedure,66 or to respect another mandate conferred by treaty. In the authors’ view, inherent judicial powers are those which are necessary to preserve the tribunal’s capacity to render a decision res judicata, with opposable legal force. In Northern Cameroons, the ICJ characterised its powers in the light of inherent judicial imperatives, removed from the will of parties: “[t]here are inherent limitations on the exercise of the judicial function which the Court, as a court of justice, can never ignore”.67

Certain Members of the Court have been significantly bolder than the ICJ itself in identifying such powers.68 Yet among disputes before inter-State courts and tribunals, these theories have found perhaps greatest application in proceedings under the WTO Dispute Settlement Understanding (DSU). The WTO Appellate Body attracted early controversy for framing the acceptance of amicus curiae briefs as falling within its “legal authority to regulate its own procedures as stipulated in Article 17.9 of the DSU” – a provision which delegates a gap-filling authority to the Appellate Body to draw up its Working Procedures.69

The Appellate Body has emphasised in especially positivist terms that neither the DSU nor its Working Procedures “explicitly prohibit[ed] acceptance or consideration of such briefs”, and instead merely required that these provisions be “communicated to the Members for their information”.70 It has linked this power to its “authority to control the process by which it informs itself both of the relevant facts of the dispute and of the legal norms and principles applicable to such facts”, considering it “indispensably necessary to enable a panel to discharge its duty imposed by DSU Article 11 to ‘make an objective assessment of the matter’”.71 Neither the Appellate Body’s Working Procedures nor WTO panels’ rules of procedure require the consent of contracting or disputing parties to adopt these texts. As such, inter-State courts other than the ICJ have looked beyond the generic terms of their constitutive instruments to prioritise NSA participation when circumstances so require.

2.3 Assessment

Based on the foregoing, we identify no clear support in formal sources of international law for a premise of necessity for NSA participation in inter-State proceedings. International courts and tribunals have thus turned to informal sources as legal channels to advance NSA participation. Courts such as the ICJ have characterised this approach as the sound administration of justice, while the WTO Appellate Body has relied upon concepts of inherent or implied judicial powers in characterising amicus curiae participation as “indispensably necessary” to the fulfilment of its mandate.72

However, the judicial reasoning constructed and articulated by inter-State courts and tribunals does not necessarily pinpoint the underlying rationales of their procedural decisions. We therefore look beneath legal sources and doctrine, to the root causes that may render NSA participation necessary in a given case.

3 Underlying Rationales for the Necessity of NSA Participation

We now turn to identify situations in which an inter-State court or tribunal may be compelled to open proceedings to NSA participation, with the objective of characterising the underlying rationales for this participation. We find that these rationales can be framed as requirements of practicality and legitimacy, and apply these lenses in turn.

In this light, the rationale of practicality reflects the short-term necessity of acquiring all relevant information needed to craft a decision, and therefore responds to the needs of effective dispute settlement. The rationale of legitimacy, on the other hand, is driven by long-term necessity. For an ad hoc tribunal, this reflects its interest in rendering a decision with which the parties will voluntarily comply. For a brick-and-mortar court, the perception that it has lost its legitimacy raises concerns regarding institutional sustainability, such as the withdrawal of member States.73

In other words, practicality speaks to what a court or tribunal must do in order to fulfil its mandate today, whereas legitimacy speaks to what it should do in order to ensure that its mandate is respected tomorrow. There is evident overlap among the two rationales of necessity in any given case. We assess cases and scenarios below to illustrate the function of either rationale, while acknowledging that both rationales may arise in some situations.

3.1 Practicality Rationales

We first draw analogy to international organisations which possess sufficient expertise to ascertain the full scope of a Member State’s international legal obligations (i.e., in order to determine whether a breach has occurred, or how such a breach should be remedied). In Certain Activities, the ICJ ordered Costa Rica to consult with the Ramsar Convention Secretariat on matters concerning damage to wetlands.74 As this concerned the implementation of provisional measures, the Secretariat thus participated in the ongoing proceedings. The participation of regional organisations (like UN organs) may in this regard be a sensible or even necessary component of the dispositif in an inter-State judgment or award.

In certain inter-State proceedings, knowledge provided by NSA s can also be considered necessary as a practical matter. Jessup observed that amicus curiae procedures may be essential to meet the ICJ’s need to obtain all information likely to throw light on the questions submitted, taking into account the adversarial nature of contentious proceedings.75 As noted above, the WTO Appellate Body developed the practice of amicus curiae on this basis, albeit over the strong opposition of some WTO Member States.76

However, inter-State courts in general have demonstrated resistance to this practice. The ICJ in particular has been reluctant to regard amicus curiae briefs as a practical necessity. NSA s have made attempts to be amici curiae in contentious proceedings such as Haya de la Torre,77 Gabčikovo-Nagymaros Project78 and Jurisdictional Immunities.79 The Court received a “myriad of [amicus curiae] briefs and memoranda”80 from non-governmental organisations in the Legality of the Threat or Use of Nuclear Weapons advisory proceedings,81 which inspired the Court’s adoption of Practice Direction XII clarifying that amicus curiae briefs from NGO s are not to be considered as part of the case file, but treated as “publications in the public domain”, and placed in a designated location in the Peace Palace.82 There is no published evidence that the Court has consulted such briefs in practice.83

For reasons of practicality, however, the ICJ has extended the framework of Article 66(2) beyond the black letter to allow other non-Members of the UN to participate, notably Kosovo and Palestine. The Court filed their submitted information as a “written contribution”, rather than the “written statements” it received from UN Member States, who are entitled to make such submissions under Article 66 of the Statute. While there would seem to be no similar room available for the submissions of non-Members of the UN, the Court justified its decision in each instance by referring to the circumstances: both Kosovo and Palestine were “the subject of the questions submitted to the Court for an advisory opinion”, and were therefore “likely to be able to furnish information on the question”.84 Thus, the participation of these non-Members was considered necessary for practical reasons.

3.2 Legitimacy Rationales

The rationale of judicial legitimacy is at times embraced in tandem with other reasons for widening participation, including legal necessity, as discussed at the outset of this article. In this light, an international court may be said to possess not merely a legal but a moral responsibility, incumbent upon the court itself.85 As claimant in the first arbitration administered by the Permanent Court of Arbitration (PCA), the United States cited a popular nineteenth century treatise on international law which had framed this in terms of personal failing: “[a]n arbitral decision may be disregarded … when [the tribunal] is guilty of an open denial of justice”.86 Schwarzenberger maintained this perspective in the mid-twentieth century, observing that when a tribunal commits an essential error of law, it “is making a cause of nullity of awards for which the tribunal is morally or intellectually responsible”.87

However, as opposed to the urgency of practical necessity, legitimacy is frustratingly intangible, particularly when viewed in moral terms. It may broadly be understood as a “right to rule”88 or an “authority (…) perceived as justified”,89 according to standards such as justice, democracy, effectiveness, or technocratic expertise.90 It is thus constructive to distinguish between standards of legitimacy applicable to inter-State courts and tribunals, with particular emphasis on democratic and technocratic standards.91 While the former is concerned with giving voice to as many constituencies of international courts as possible, and acknowledges the political character of these institutions, the latter is derived from the expertise, competence, knowledge, skills, and reputation of judges and court officials, and values adjudication as a depoliticised process.92

In other words, a technocratically legitimate court operates in conditions which enable objective and careful study as to what reason and justice require.93 The 2021 Judgment of the International Tribunal for the Law of the Sea (ITLOS) in Mauritius/Maldives is perhaps the first international judicial decision to frame this point so emphatically.94 By relying on a concept of authoritativeness based on the “rigour and scrutiny” of ICJ Advisory Opinions, the ITLOS Special Chamber employed technocratic considerations of institutional process.95 It thus defined the legal in contrast to the political: the Chagos Opinion has opposable legal effect because its creative process ensured against politicisation. By bridging the gap between the binding or merely advisory effect of international legal decisions, the Chamber thus encouraged comparative reference to advisory opinions when assessing the value of NSA participation in contentious proceedings.96

Nevertheless, democratic standards remain a more appropriate yardstick than technocratic standards to measure the necessity of NSA participation. In this respect, we recall that inter-State courts and tribunals ensure an equality of parties wherein neither party lays claim to “civil society”.97 In cases before inter-State courts which arise from the rights or treatment of a specific person, however, a court’s holdings will have repercussions for the rights and treatment of others in similar situations. The aforementioned ICJ Advisory Opinions in response to applications for the review of UN administrative proceedings illustrate this point. The importance of civil society in such cases arises from the general premise that international courts are law-making bodies, as well as the premise that the legitimacy of law may be affected by the participation (or non-participation) of civil society in law-making.98 In this light, giving voice to the individual by conferring procedural rights improves the democratic legitimacy of the judicial institution.

Before the ICJ, it has often been left to the parties themselves to ensure the democratic legitimacy of the proceedings. In the Chagos advisory proceedings, Mauritius considered it appropriate that “the Court should hear the voice of the Chagossians directly”.99 Thus, a group of Chagossians representing their community not only attended the oral hearings, but also made a statement during Mauritius’s speaking time.100 As counsel for Mauritius, Sands specified that this statement was “not offered as testimonial evidence, but simply as a member of the delegation of Mauritius – if you like – a statement of impact, what the continuation of colonialism really means for real people”.101 This initiative embodies the central concern of democratic legitimacy in legal proceedings: the public participation of those directly impacted by the outcome of these proceedings. Analogy may be drawn to the Court’s decision to receive submitted information from Kosovo and Palestine in their respective advisory proceedings.102

Other inter-State courts and tribunals have arguably taken measures indicating their concern for democratic legitimacy. If we examine the WTO’s approach to amicus curiae briefs explained above, the WTO Appellate Body confirmed the right to receive such briefs in cases such as EC–Asbestos.103 It even allowed an unsolicited brief from Morocco in EC–Sardines, who requested to be heard as an amicus curia as opposed to a third party.104 Therefore, a primary reason to accept amicus curiae briefs – especially in light of opposition from Member States – is the importance of democratic legitimacy, access and involvement in proceedings that yield significant consequences for civil society. As stated by the WTO itself, “the period since the creation of the WTO has vividly demonstrated that the multilateral trading system is being scrutinised by public opinion like never before”.105

ITLOS allows unsolicited amicus curiae briefs from intergovernmental organisations in contentious proceedings, per Article 84(2) of its Rules of Procedure.106 While its Rules do not invite unsolicited amicus curiae briefs from non-governmental organisations in advisory proceedings,107 the Tribunal nevertheless authorized NSA participation in the Responsibilities and Obligations of States Sponsoring Persons and Entities with Respect to Activities in the Area advisory proceedings.108 Greenpeace and the World Wide Fund for Nature (WWF) submitted statements in these proceedings, which were transmitted to States, intergovernmental organisations, and the International Seabed Authority.109 They were also published on the ITLOS website in the same manner as other submitted documents.110 In this light, the Tribunal’s decision to widely circulate and publish the amicus curiae briefs submitted by Greenpeace and the WWF may be viewed as a measure to preserve democratic legitimacy, given the indisputable public interest in the seabed resources that lie beyond national jurisdiction (“the common heritage of mankind”).111

Greenpeace was more directly affected by the events of the Arctic Sunrise case, and sought to submit an amicus curiae brief to ITLOS in those proceedings. ITLOS refused this submission following Russia’s objection, upon the grounds that Greenpeace was an NGO.112 Greenpeace was, however, permitted to give testimony upon the request of the Dutch government.113 While it is unclear whether Greenpeace had similarly sought to participate in the Rainbow Warrior arbitrations between France and New Zealand, such participation would not have significantly enhanced the perceived legitimacy of these proceedings, given that France had consented to arbitrate directly with Greenpeace in a parallel case.114 These examples illustrate how a court or tribunal may seek to ensure its democratic legitimacy through different procedural channels, so long as the relevant constituency is given a voice in the matter.

While organisations and other non-Members of the UN have participated out of necessity before inter-State judicial bodies, we must acknowledge that no such practice has indicated the necessity of individual participation in proceedings. While the ICJ circumvented Article 66(2) to allow Kosovo and Palestine to furnish information, it did not take similar measures to allow for injured UN staff members to do likewise in instances where they were at the centre of the legal matter. The furthest international courts and tribunals have gone is to ensure that their decisions would not impact the rights of indigenous or stateless peoples, as was done at the PCA in Abyei,115 or by the ICJ in Burkina Faso/Niger.116

It cannot be ruled out that such participation may become necessary in future disputes, however. We observe in this light that individuals may, under some circumstances, indirectly contribute to the creation of customary international law.117 As Judge Van den Wyngaert stated in her Arrest Warrant dissent nearly 20 years ago, “the opinion of civil society [cannot be] completely discounted in the formation of customary international law today”.118 The ICJ may therefore need to verify the facts of local practices in order to determine the existence of a customary rule and apply it correctly, despite having waived similar opportunities in cases such as Navigational and Related Rights.119 In such instances, we may view this participation or communication as essential to the ICJ’s ability to fulfil its mandate under Article 38 of the Statute.

NSA participation may also become particularly salient in cases concerning humanitarian law or grave human rights violations. By finding that The Gambia possessed prima facie standing to institute the pending Genocide case against Myanmar,120 the ICJ demonstrated increased openness to public interest litigation (i.e., in cases of obligations erga omnes partes). Yet The Gambia’s lack of direct injury or connection to facts on the ground highlights the proportionately greater need to hear from local voices in such cases. This participation would not only fulfil a practical need, but also reflect a rationale of democratic legitimacy in involving NSA s directly impacted by the outcome of the proceedings.

4 Conclusion

Where NSA s have been involved in inter-State cases, such participation often arises through the facilitation of a party to the dispute. Irrespective of government support, however, NSA participation may in some scenarios be considered critical to the effectiveness of an institutional court’s or tribunal’s work. In such circumstances, these bodies enjoy discretion to determine how to resolve this tension within their respective procedural frameworks, so long as the NSA is given a voice in the proceedings.

In the present article, we have seen that the ICJ and other inter-State courts have admitted NSA participation more clearly on the basis of informal legal sources than through the formal sources of international law recognised in Article 38 of the ICJ Statute. Lifting the veil of judicial reasoning to remove doctrinal explanations such as the sound administration of justice and inherent powers,121 we observe two underlying rationales which such courts may embrace by necessity, as seen when they permit NSA s to participate in the proceedings without the parties’ consent, or without express authority in these courts’ constitutive treaties.

In the authors’ view, the ICJ should focus on the Statute’s absence of clear prohibitions to the participation of non-parties (including NSA s), rather than dwell on a lack of provisions clearly governing such participation. This would wisely give maximum effect to the consent of UN Members in establishing a living, permanent judicial organ, and thus afford the Court maximum flexibility to ensure and preserve the legal validity of its decisions. Just as critically, this approach empowers the Court to obtain sufficient information and stakeholder participation to ensure the effectiveness – and perceived legitimacy – of its proceedings.


See Francisco Orrego Vicuña, “Individuals and Non-State Entities before International Courts and Tribunals”, 5 Max Planck Yearbook of United Nations Law (2001), 53–66; Eric De Brabandere, “Pragmatism in International Law: Non-State Actor Participation in International Dispute Settlement”, in J. d’Aspremont (ed.), International Legal System: Multiple Perspectives on Non-State Actors in International Law (Routledge, 2011).


We employ the commonplace meaning of necessity, rather than legalised definitions which may find theoretical application to institutional courts. See International Law Commission, Draft Articles on the Responsibility of International Organizations, Yearbook of the International Law Commission (2011), Vol. II(2), Art. 25 (concerning “an essential interest [of] the international community”).


While the International Court of Justice has been more receptive to NSA participation in advisory proceedings than in contentious proceedings (e.g., the participation of the African Union during the written and oral phases of Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, Advisory Opinion, I.C.J. Reports 2019, p. 95), overlaps between these two judicial functions are apparent. Cf. ibid., paras. 83–91 (“Whether the questions asked relate to a pending dispute between two States, which have not consented to its settlement”); discussion infra regarding the 2021 Judgment of the International Tribunal for the Law of the Sea in Mauritius/Maldives. See further Yaël Ronen, “Participation of Non-State Actors in ICJ Proceedings”, 11(1) The Law & Practice of International Courts and Tribunals (2012), 77–110.


The present article applies this label to any purported legal source which is not codified in Article 38(1)(a)–(c) of the Statute. On the limitation of “formal” sources to these provisions, see, e.g., Hugh Thirlway, The Sources of International Law (2014), 117.


The compromis cannot contravene rules dictated by a court’s statute – this would be “tantamount to functional nullity”. Robert Kolb, Peremptory International Law – Jus Cogens: A General Inventory (2015), 105–106. On the “arbitralisation” of the Court, see Georges Abi-Saab, “The International Court as a World Court”, in V. Lowe and M. Fitzmaurice (eds.), Fifty Years of the International Court of Justice: Essays in Honour of Sir Robert Jennings (1996) 3, 9–11.


While these may provide for a court’s appointment of experts, such mechanisms are irrelevant to NSA s seeking entry to the proceedings on their own accord, to voice their own concerns. See, e.g., ICJ Statute, Art. 50.


In the International Status of South West Africa 1950 advisory proceedings, the Court accepted a request to provide information in accordance with Article 66(2) by an NGO, interpreting that it was an “intergovernmental organisation”. See International Status of South West Africa, Advisory Opinion, I.C.J. Reports 1950, p. 128, Correspondence (19 December 1949), p. 327; see further Legal Consequences for States of the Continued Presence of South Africa in Namibia (South West Africa) notwithstanding Security Council Resolution 276 (1971), Correspondence (29 July 1970), p. 638.


For the purposes of the present inquiry, we put aside the theoretical possibility that member States may acquiesce to the judicial development of NSA participation through rules of court. From that perspective, an absence of protest to the publication of rules can “bless” such rules with normative force (even when they reflect an interpretation of the court’s statute which is ultra vires on its face).


See Vienna Convention on the Law of Treaties (23 May 1969, entered into force 27 January 1980), United Nations, Treaty Series, Vol. 1155, p. 331, Arts. 53, 64.


Peter Schlosser, “La procédure des voies de recours en matiere d’arbitrage”, Revue de L’Arbitrage (1978), 345–357 (“Expressed differently, a void award does not as such acquire validity by the mere passage of time”).


Lori F. Damrosch, “A Comparative Look at Domestic Enforcement of International Decisions”, 103 American Society of International Law Proceedings (2009), 39.


Edvard Hambro, L’exécution des sentences internationales (1936), 2–20.


See Arbitral Award of 31 July 1989 (Guinea-Bissau v. Senegal), Judgment, I.C.J. Reports 1991, Dissenting Opinion of Judge Weeramantry, p. 130, 160; James L. Brierly, “The Hague Conventions and the Nullity of Arbitral Awards”, 9 British Yearbook of International Law (1928), 115.


International Law Commission, Draft on arbitral procedure adopted by the Commission at its fifth session Report by Georges Scelle, Special Rapporteur (Document A/CN.4/113), Yearbook of the International Law Commission (1958), Vol. II (A/CN.4/SER.A/1958/Add.l), Art. 35(c).


Arbitral Award made by the King of Spain on 23 December 1906 (Honduras v. Nicaragua), Judgment, I.C.J. Reports 1960, p. 192, 216.


Kenneth S. Carlston, The Process of International Arbitration (1946), 40–42; Bin Cheng, General Principles of Law as Applied by International Courts and Tribunals (1953), 290–298. See further Ping-Lang Chao, The Finality of International Arbitral Awards (1955).


Kaiyan Homi Kaikobad, “Nullity and Validity: Challenges to Territorial and Boundary Judgments and Awards”, in Jin-Hyuan Paik et al. (eds.), Asian Approaches to International Law and the Legacy of Colonialism: The Law of the Sea, Territorial Disputes and International Dispute Settlement (2012), 73, 116–121.


In an early investor-State example, questions arose in the Lazare arbitration as to whether Haiti had prevented US nationals from fulfilling the terms of a contract. Text reprinted in John Bassett Moore, History and Digest of International Arbitrations to which the United States has been a Party (Vol. 2, 1898), 1786.


For contexts where an NSA’s participation may assist in ascertaining its nationality, see the pending case of Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia), Preliminary Objections, Judgment, I.C.J. Reports 2016, p. 100. Colombia claims the Raizales indigenous population of San Andrés island are Colombian nationals with ancestral fishing rights. Suggesting the application of procedural estoppel, see Oral statements, Public sitting held on Friday 9 October 2015, at 10 a.m., at the Peace Palace, Verbatim record 2015/29, paras. 30–31 (Argüello Gómez). Finding that a treaty in force between the parties left it unnecessary to assess the nationality and practices of local tribesmen in the disputed area (for the purpose of determining prescriptive title), see also Territorial Dispute (Libyan Arab Jamahiriya/Chad), Judgment, I.C.J. Reports 1994, p. 6.


Text reprinted in Moore, supra note 18, 2589. See further Yousef Issa Youakim, Estoppel in International Law (1969), 252–254.


See International Law Commission, Draft Articles on Diplomatic Protection, Yearbook of the International Law Commission (2006), Vol. II(2), Arts. 1–13. See also P.C.I.J., Series A/B, Panevezys-Saldutiskis Railway, Judgment of 28 February 1939, p. 16.


Barcelona Traction, Light and Power Company, Limited, Judgment, I.C.J. Reports 1970, p. 44. For broader questions arising from allegations of fraudulent evidence before the ICJ, see M. Beth Olsen (ed.), The Forensics of a Forgery: Bahrain’s Submissions to the International Court of Justice in re: Qatar v. Bahrain (2003); Paul S. Reichler, “The Nicaragua Case: A Response to Judge Schwebel”, 106(2) American Journal of International Law (2012), 316.


Status of Eastern Carelia, Advisory Opinion, P.C.I.J., Series B, No. 5 (1923), 7. This also recalls Judge Anzilotti’s view in Danzig, where he found that the PCIJ should not have given its opinion because deviations from fundamental rules of procedure fall outside of the scope of the Permanent Court’s functions. Consistency of Certain Danzig Legislative Decrees with the Constitution of the Free City, Advisory Opinion, P.C.I.J., Series A/B, No. 65 (1935), Individual Opinion of Judge Anzilotti, p. 60.


Hersch Lauterpacht, The Function of Law in the International Community (1933), 68–72.


Craig Eggett, “The Role of Principles and General Principles in the ‘Constitutional Processes’ of International Law”, 66(2) Netherlands International Law Review (2019), 197–217.


Theodor Meron, The Humanization of International Law (2006), 383–384.


Carol Harlow, “Global Administrative Law: The Quest for Principles and Values”, 17(1) European Journal of International Law (2006), 187, 195. For scholars of global administrative law who take a dimmer view of the potential relevance of general principles of law, see Benedict Kingsbury, Nico Krisch and Richard B. Stewart, “The Emergence of Global Administrative Law”, 68(3/4) Law and Contemporary Problems (2005), 29 (observing that their identification and practice has been “limited mainly to the internal needs of international institutions”).


See United States – Import Prohibition of Certain Shrimp and Shrimp Products, Report of the Appellate Body (WT/DS58/AB/R, 12 October 1998), para. 16.


See CJEU, Union Nationale des Entraineurs et Cadres Techniques Professionnels du Football (UNECTEF) v. Georges Heylens and Others (Case 222/86), 15 October 1987, European Court Reports 1987, p. 04097.


Finding general principles applicable to a wider range of bodies with law-making powers, see Bardo Fassbender, Targeted Sanctions and Due Process: The responsibility of the UN Security Council to ensure that fair and clear procedures are made available to individuals and entities targeted with sanctions under Chapter VII of the UN Charter (United Nations, 2006) (observing that due process is applicable to “international organizations as subjects of international law when those organizations exercise ‘governmental authority’ over individuals”).


Identifying two “categories of general principles of law” in this light, see International Law Commission, First report on general principles of law by Marcelo Vázquez-Bermúdez, Special Rapporteur (A/CN.4/732), 71st session, 5 April 2019, 75 (Draft Conclusion 3).


Charles T. Kotuby, Jr. and Luke A. Sobota, General Principles of Law and International Due Process: Principles and Norms Applicable in Transnational Disputes (2017), 1.


Wolfgang Friedmann, “The Uses of ‘General Principles’ in the Development of International Law”, 57(2) American Journal of International Law (1963), 290 (defining these as “certain minimum standards in the administration of justice of such elementary fairness and general application in the legal systems of the world that they have become international legal standards”).


See, e.g., Inter-American Court of Human Rights, Castillo Petruzzi and Others v. Peru (1999), para. 128; Inter-American Court of Human Rights, Cantoral Benavides v. Peru (2000), para. 112.


Ian Brownlie, “The Individual Before Tribunals Exercising Jurisdiction”, 11 International & Comparative Law Quarterly (1962), 719. On the critical role NSA s play in buttressing the effectiveness of international courts and tribunals more broadly, see Cassandra Steer, “Non-state actors in international criminal law”, in J. d’Aspremont (ed.), Participants in the International Legal System: Multiple Perspectives on Non-State Actors in International Law (2011), 295, 297.


See, e.g., Astrid Wiik, Amicus Curiae before International Courts and Tribunals (Nomos, 2018), 178–179. But see Corfu Channel (United Kingdom of Great Britain and Northern Ireland v. Albania), Merits, I.C.J. Reports 1949, p. 4, 22 (placing a specific “principle of the freedom of maritime communication” alongside other “elementary considerations of humanity”).


On the ne infra petita principle, see Attila Tanzi, “On judicial autonomy and the autonomy of the parties in international adjudication, with special regard to investment arbitration and ICSID annulment proceedings”, 33(1) Leiden Journal of International Law (2019), 57.


Bin Cheng, General Principles of Law as Applied by International Courts and Tribunals (1987).


See Meron, supra note 26.


Prosper Weil, Le Droit International en Quête de son Identité (2006), 353–354.


Robert Jennings and Arthur Watts (eds.), Oppenheim’s International Law (9th edition, 1992), 16.


See discussion in Astrid Wiik, supra note 36, 83, n. 345. See further Laurence Boisson de Chazournes, “Transparency and amicus curiae briefs”, 5 Journal of World Investment and Trade (2004), 333–336.


Among major ICJ contributions to the development of this concept, see Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), Merits, Judgment, I.C.J. Reports 1986, p. 14; East Timor (Portugal v. Australia), Judgment, I.C.J. Reports 1995, p. 90; Questions relating to the Obligation to Prosecute or Extradite (Belgium v. Senegal), Judgment, I.C.J. Reports 2012, p. 422.


Julia Werzer, “The UN Human Rights Obligations and Immunity: An Oxymoron Casting a Shadow on the Transitional Administrations in Kosovo and East Timor”, 77(1–2) Nordic Journal of International Law (2008), 117–118.


See International Law Commission, Fourth report on peremptory norms of general international law (jus cogens) by Dire Tladi, Special Rapporteur (A/CN.4/727), 71st session, 31 January 2019, paras. 54–115.


Ibid., paras. 123, 134.


See, e.g., Nada (Youssef) v. State Secretariat for Economic Affairs and Federal Department of Economic Affairs, Administrative Appeal Judgment, Swiss Federal Tribunal, 14 November 2007 (No. 1A 45/2007); AA v. Austria, Judgment, Supreme Court of Justice of Austria, 30 September 2008 (No. 1Ob225/07f).


For example, providing a right of access to natural or juridical persons in disputes concerning the International Seabed Area: see United Nations Convention on the Law of the Sea (10 December 1982, entered into force 16 November 1994), United Nations, Treaty Series, Vol. 1833, p. 3, Art. 187 [UNCLOS].


PCIJ Advisory Committee of Jurists, Procès-Verbaux, 1920, p. 713.


Aurélia Lelarge, “L’émergence d’un principe de bonne administration de la justice internationale dans la jurisprudence internationale antérieure à 1945”, 27 L’Observateur Des Nations Unies (2009), 27–28.


Carlo Focarelli, “Denial of Justice”, in Max Planck Encyclopedias of International Law [MPIL] (2015); Hans W. Spiegel, “Origin and Development of Denial of Justice”, 32(1) American Journal of International Law (1938), 63–81.


Lelarge, supra note 50.


Robert Kolb, “General Principles of Procedural Law”, in Andreas Zimmermann, Christian J. Tams, Karin Oellers-Frahm and Christian Tomuschat (eds.), The Statute of the International Court of Justice: A Commentary (3rd edition, 2019), 970. Treating the sound administration of justice as “in itself (and not only in the formal category as ‘general principle of law’) a type of source of the law”, see ibid., 965, n. 4.


See Legality of Use of Force (Serbia and Montenegro v. Belgium), Provisional Measures, Order of 2 June 1999, I.C.J. Reports 1999, para. 44 (finding that invoking a new basis of jurisdiction during oral arguments “seriously jeopardizes the principle of procedural fairness and the sound administration of justice”). On the essential role of procedural principles in the preservation of justice, see Filippo Fontanelli and Paolo Busco, “The Function of Procedural Justice in International Adjudication”, 15(1) The Law & Practice of International Courts and Tribunals (2016), 1–23.


Kolb, supra note 53, at 806, 970.


Ibid., 977.


See, e.g., Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Croatia v. Serbia), Preliminary Objections, Judgment, I.C.J. Reports 2008, para. 85; Maritime Delimitation in the Caribbean Sea and the Pacific Ocean (Costa Rica v. Nicaragua) and Land Boundary in the Northern Part of Isla Portillos (Costa Rica v. Nicaragua), Order of 2 February 2017, I.C.J. Reports 2017, para. 16; Application of the International Convention for the Suppression of the Financing of Terrorism and of the International Convention on the Elimination of All Forms of Racial Discrimination (Ukraine v. Russian Federation), Order of 19 April 2017, I.C.J. Reports 2017, Separate Opinion of Judge Cançado Trindade, para. 81; Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia), Judgment of 17 March 2016, I.C.J. Reports 2016, Joint Dissenting Opinion of Vice-President Yusuf, Judges Cançado Trindade, Xue, Gaja, Bhandari, Robinson and Judge ad hoc Brower, para. 65.


See Application for Review of Judgment No. 158 of the United Nations Administrative Tribunal, Advisory Opinion, I.C.J. Reports 1973, p. 166; Application for Review of Judgment No. 273 of the United Nations Administrative Tribunal, Advisory Opinion, I.C.J. Reports 1982, p. 325; Application for Review of Judgment No. 333 of the United Nations Administrative Tribunal, Advisory Opinion, I.C.J. Reports 1987, p. 18.


See United Nations General Assembly Resolution 50/54 of 11 December 1995 (A/RES/50/54).


See Judgments of the Administrative Tribunal of the ILO upon Complaints Made against UNESCO, Advisory Opinion, I.C.J. Reports 1956, p. 77; Judgment No. 2867 of the Administrative Tribunal of the International Labour Organization upon a Complaint Filed against the International Fund for Agricultural Development, Advisory Opinion, I.C.J. Reports 2012, p. 10.


See Judgment No. 2867 of the Administrative Tribunal of the International Labour Organization upon a Complaint Filed against the International Fund for Agricultural Development, Advisory Opinion, I.C.J. Reports 2012, Declaration of Judge Greenwood, para. 4; International Labour Office, Matters relating to the Administrative Tribunal of the ILO; Proposed amendments to the Statute of the Tribunal (GB.326/PFA/12/1, 18 February 2016), pp. 1–2, <>, last accessed 27.01.2022.


United Nations General Assembly, Resolution of 8 November 1955 (A/RES/957(X)), Art. 11.


International Labour Office, Resolution concerning the Statute of the Administrative Tribunal of the International Labour Organization (7 June 2016), <>, last accessed 27.01.2022.


For example, in Application for Review of Judgment No. 273 of the United Nations Administrative Tribunal, Advisory Opinion, I.C.J. Reports 1982, paras. 6, 8.


For example, Judgments of the Administrative Tribunal of the ILO upon Complaints Made against UNESCO, Advisory Opinion, I.C.J. Reports 1956, p. 86.


In the context of invalid awards, see Arpad Balasko, Causes de nullité de la sentence arbitrale en droit international public (1938), 194.


Northern Cameroons (Cameroon v. United Kingdom), Preliminary Objections, I.C.J. Reports 1963, p. 29.


See, e.g., Nuclear Tests (Australia v. France), Judgment, I.C.J. Reports 1974, Joint Dissenting Opinion of Judges Onyeama, Dillard, Jiménez de Aréchaga, and Sir Humphrey Waldock, p. 312, para. 22 (“[T]here is a basic contradiction when the Court invokes its ‘inherent jurisdiction’ and its ‘judicial character’ to justify its disposal of the case, while, at the same time, failing to accord the Applicant any opportunity whatever to present a countervailing argument”); Certain Activities Carried Out by Nicaragua in the Border Area (Costa Rica v. Nicaragua), Joinder of Proceedings, Order of 17 April 2013, I.C.J. Reports 2013, Separate Opinion of Judge Cançado Trindade, p. 172, para. 14 (characterising inherent powers as serving to “ensur[e] procedural equality and the guarantees of due process”).


European Communities – Trade Description of Sardines, Report of the Appellate Body (WT/DS231/AB/R, 26 September 2002), para. 166. See further Friedl Weiss, “Inherent Powers of National and International Courts”, in F. Ortino and E.-U. Petersmann, The WTO Dispute Settlement System, 1995–2003 (2004), 177, 180.


United StatesImposition of Countervailing Duties on Certain Hot-Rolled Lead and Bismuth Carbon Steel Products Originating in the United Kingdom, Report of the Appellate Body (WT/DS138/AB/R, 10 May 2000), para. 39 (finding it has “legal authority to decide whether or not to accept and consider any information [it] believe[s] is pertinent and useful in an appeal”, though no DSU article expressly confers this authority upon it).


US – Shrimp, supra note 28, para. 106. See further Chang-Fa Lo, Treaty Interpretation Under the Vienna Convention on the Law of Treaties: A New Round of Codification (2017), 112–114.


US – Shrimp, ibid.


On the legitimacy of inter-State courts with regards to NSA participation, see: Cedric Ryngaert, “Non-State Actors: Carving out a Space in a State-Centred International Legal System”, 63 Netherlands International Law Review (2016), 183–195; Nienke Grossmann, “The Normative Legitimacy of International Courts”, 86 Temple Law Review (2013), 61; Laurence Boisson de Chazournes and Makane Moïse Mbengue, “L’‘amicus curiae’ devant l’organe de règlement de différends de L’OMC”, in S. Maljean-Dubois, Droit de l’organisation mondiale du commerce et protection de l’environnement, Travaux Du CERIC 2 (Bruylant, 2003), 400–443.


See Certain Activities Carried Out by Nicaragua in the Border Area (Costa Rica v. Nicaragua), Order of 8 March 2011, I.C.J. Reports 2011, para. 86(2).


Philip C. Jessup, “Intervention in the International Court”, 75 American Journal of International Law (1981), 903, 909. See also J.T. Miller, “Intervention in Proceedings Before the International Court of Justice”, in L. Gross (ed.), The Future of the International Court of Justice, Vol. II (1976), 560; Christine Chinkin, Third Parties in International Law (1993), 515, n. 83.


See WTO Website, “Participation in dispute settlement proceedings”, available at: wto .org/english/tratop_e/dispu_e/disp_settlement_cbt_e/c9s3p1_e.htm#fnt2, last accessed 27.01.2022.


Haya de la Torre (Colombia v. Peru), I.C.J. Reports 1950, Correspondence (8 October 1949), pp. 227–228.


See Luigi Crema, “Testing Amici Curiae in International Law: Rules and Practice”, 22(1) The Italian Yearbook of International Law Online (2013), 121; Eric De Brabandere, “NGO s and the ‘Public Interest’: The Legality and Rationale of Amicus Curiae Interventions in International Economic and Investment Disputes”, 12(1) Chicago Journal of International Law (2011), 94.


See Bruno Simma, “Human Rights Before the International Court of Justice: Community Interest Coming to Life?”, in: C. J. Tams and J. Sloan (eds.), The Development of International Law by the International Court of Justice (2013), 316, n. 63.


Rosalyn Higgins, “Remedies and the International Court of Justice”, in R. Higgins, Themes and Theories (2009), 894.


Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, I.C.J. Reports 1996, Dissenting Opinion of Judge Guillaume, pp. 287–288, para. 2.


The ICJ has enhanced the value of such submissions by making clear that third-State interveners do not serve to provide general information in contentious cases. See, e.g., Continental Shelf (Tunisia/Libya), Application to Intervene, Judgment, I.C.J. Reports 1981, p. 3, para. 31. Instead embracing an “informational function” for State intervention, see Zachary Mollengarden and Noam Zamir, “The Monetary Gold Principle: Back to Basics”, 115 American Journal of International Law (2021), 41, 63.


See the equivocal (yet unprecedented) statement from the Court’s former Registrar, in Eduardo Valencia-Ospina, “Court Clarification: Letters to the Editor”, International Herald Tribune, 15 November 1995 (“The court would like to make it clear that all such documents are given consistent treatment”).


Accordance with International Law of the Unilateral Declaration of Independence by the Provisional Institutions of Self-Government of Kosovo, Order of 17 October 2008, I.C.J. Reports 2008, p. 409, para. 4. Similar wording is found in Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Order of 19 December 2003, I.C.J. Reports 2003, para. 4.


On these “humanitarian considerations”, see Hugh Thirlway, The International Court of Justice (2016), 29–31.


Pious Fund of the Californias (United States v. Mexico), Statement and Brief on Behalf of the United States, reprinted in US Department of State, Foreign Relations of the United States 1902, App. II (1903), 199, 224 (quoting William Edward Hall, International Law (1880), 379) [emphasis added].


Georg Schwarzenberger, International Law as Applied by International Courts and Tribunals, Vol. I (2nd edition, 1949), 470 [emphasis added].


Allen Buchanan, “The Legitimacy of International Law”, in S. Besson and J. Tasioulas (eds.), The Philosophy of International Law (2010), 79; Daniel Bodansky, “Legitimacy in International Law and International Relations”, in J.L. Dunoff and M.A. Pollack (eds.), Interdisciplinary Perspectives on International Law and International Relations: The State of the Art (2013), 324; Daniel Bodansky, “The Concept of Legitimacy in International Law”, in R. Wolfrum and V. Röben (eds.), Legitimacy in International Law (2008), 313; Harlan Grant Cohen, Andreas Follesdal, Nienke Grossman and Geir Ulfstein, “Legitimacy and International Courts – A Framework”, in N. Grossman, H.G. Cohen, A. Follesdal and G. Ulfstein (eds.), Legitimacy and International Courts (2018), 3.


Daniel Bodansky, “The Legitimacy of International Governance: A Coming Challenge for International Environmental Law?”, 93 American Journal of International Law (1999), 596, 596 n. 3, 600; Nienke Grossman, “Legitimacy and International Adjudicative Bodies”, 41 George Washington International Law Review 107 (2009), 5.


See further Harlan Grant Cohen, Andreas Follesdal, Nienke Grossman and Geir Ulfstein, “Legitimacy and International Courts – A Framework”, in N. Grossman, H.G. Cohen, A. Follesdal and G. Ulfstein (eds.), Legitimacy and International Courts (2018), 3. “Moral legitimacy” has also been separately identified in Nienke Grossman, “Legitimacy and International Adjudicative Bodies”, 41 George Washington International Law Review 107 (2009), 5.


Scholars categorise these ideas somewhat differently. Grossmann, for instance, opines that an international court is legitimate when it is “(1) fair and unbiased, (2) interpreting and applying norms consistent with what states believe the law is or should be, and (3) transparent and infused with democratic norms.” Nienke Grossman, “Legitimacy and International Adjudicative Bodies”, 41 George Washington International Law Review 107 (2009), 5.


In the context of judicial appointment, see R. Daniel Kelemen, “Selection, Appointment, and Legitimacy: A Political Perspective”, in M. Bobek (ed.), Selecting Europe’s Judges: A Critical Review of the Appointment Procedures to the European Courts (2015), 245; Brian McGarry and Josef Ostřanský, “Before the Law: Assessing the Process and Impact of Judicial Screening Bodies”, in F. Baetens (ed.), Legitimacy of Unseen Actors in International Adjudication (2019), 189.


Synthesising the views of Grotius, Vattel, and Wheaton, see Mortimer N.S. Sellers, “The Purpose of International Law Is to Advance Justice – and International Law Has No Values Unless It Does So”, 111 American Society of International Law Proceedings (2017), 301, 304.


In the words of one Member of the Chamber, “[t]he moment courts and tribunals stop thinking about legitimacy, they are in trouble”. See “National University of Singapore Centre for International Law – American Society of International Law Practitioner Colloquium on Maritime Delimitation as a Judicial Process”, 27 May 2021, <> [at 1h 56m30s].


Delimitation of the Maritime Boundary between Mauritius and Maldives in the Indian Ocean (Mauritius/Maldives), ITLOS Case No. 28, Preliminary Objections, Judgment of 28 January 2021, paras. 203–205 (“[J]udicial determinations made in advisory opinions carry no less weight and authority than those in judgments because they are made with the same rigour and scrutiny by the ‘principal judicial organ’ of the United Nations […] The Special Chamber considers that those determinations do have legal effect”).


But see, empirically testing distinct tendencies in the deliberation of questions in abstracto versus in concreto, Piotr Bystranowski et al., “Do Formalist Judges Abide by Their Abstract Principles? A Two-Country Study in Adjudication”, 1–33 International Journal for the Semiotics of Law (2021) [advance access].


Characterising the concept of civil society as “chimerical, in particular in an international law context”, see Farouk El-Hosseny, Civil Society in Investment Treaty Arbitration: Status and Prospects (2018), 8.


See Jean d’Aspremont, “Subjects and Actors in International Lawmaking: The Paradigmatic Divides in the Cognition of International Norm-Generating Processes”, in C. Brölmann and Y. Radi (eds.), Research Handbook on the Theory and Practice of International Lawmaking (Elgar, 2016), 32–55; Paul Schiff Berman, “Non-State Law Making through the Lens of Global Legal Pluralism”, in M.A. Helfand (ed.), Negotiating State and Non-State Law: The Challenge of Global and Local Legal Pluralism (2015), 15–40; Andrea Bianchi, “Law Making”, in A. Bianchi (ed.), Non-State Actors and International Law (Routledge, 2009). Likening judicial law-making to the function of a democratically elected parliament – but emphasising in this respect the technocratic value of parliamentary rules – see Joseph Raz, “Law and Value in Adjudication”, in J. Raz, The Authority of Law: Essays on Law and Morality (2nd edition, 2009), 180, 197–198.


Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, Advisory Opinion of 25 February 2019, Oral statements, Public sitting held on Monday 3 September 2018, at 10 a.m., at the Peace Palace, Verbatim record 2018/20, pp. 71–72, para. 4 (Philippe Sands).


Ibid., para. 20 (Sir Anerood Jugnauth).


Supra note 97.


See Kosovo, supra note 84, at 410; Wall, supra note 84, at 429–430.


European Communities – Measures Affecting Asbestos and Products Containing Asbestos, Report of the Appellate Body (WT/DS135/AB/R, 12 March 2001), paras. 51–52 (discussing the Appellate Body’s adoption of an Additional Procedure requiring amici curiae to file applications for leave to submit briefs). For a comprehensive analysis of the WTO’s approach to such briefs, see “WTO Analytical Index (DSU – Article 13/Appendix 4 (Jurisprudence))”, <>, last accessed 27.01.2022.


European Communities – Trade Description of Sardines, Report of the Appellate Body (WT/DS231/AB/R, 26 September 2002), para. 19.


World Trade Organization, “Relations with Non-Governmental Organizations/Civil Society”, <>, last accessed 27.01.2022.


ITLOS, Rules of the Tribunal (last amended 25 March 2021), available at <>, last accessed 27.01.2022.


Ibid., Article 133(2).


Responsibility and Obligations of States Sponsoring Persons and Entities with Respect to Activities in the Area, Advisory Opinion, ITLOS Case No. 17, 1 February 2011, para. 13.




See ITLOS website, Case No. 17, under “Other Statements and Further Information”, <itlos .org/index.php?id=109>, last accessed 27.01.2022.


Article 136, UNCLOS (supra note 48).


The “Arctic Sunrise” Case (Kingdom of the Netherlands v. Russian Federation), ITLOS Case No. 22, Order of 22 November 2013, paras. 15–19.


Ibid., para. 28.


Recalling these various proceedings from his perspective as an arbitrator, see Claude Reymond, “The Rainbow Warrior Arbitration between Greenpeace and France”, 9 Journal of International Arbitration (1992), 91.


Delimitation of the Abyei Area between the Government of Sudan and the Sudan People’s Liberation Movement/Army, Award of 22 July 2009, UNRIAA, Vol. XXX, p. 145, para. 753 (“the transfer of sovereignty in the context of boundary delimitation should not be construed to extinguish traditional rights to the use of land (or maritime resources)”.


Frontier Dispute (Burkina Faso/Mali), Judgment, I.C.J. Reports 2013, p. 44, para. 112 (“each Party […] should have due regard to the needs of the populations concerned, in particular those of the nomadic or semi-nomadic populations”). See further Yusra Suedi, “Man, Land and Sea: Local Populations in Territorial and Maritime Disputes before the International Court of Justice”, 20 The Law & Practice of International Courts and Tribunals (2021), 30–53.


International Law Commission, Draft Conclusions on the Identification of Customary International Law with commentaries, Yearbook of the International Law Commission (2018), Vol. II(2), Draft Conclusion 4, Comment (8) (recognising that the conduct of NSA s “may have an indirect role in the identification of customary international law, by stimulating or recording the practice and acceptance as law (opinio juris) of States and international organisations. For example, the acts of private individuals may sometimes be relevant to the formation or expression of rules of customary international law, but only to the extent that States have endorsed or reacted to them”).


Arrest Warrant of 11 April 2000 (Democratic Republic of the Congo v. Belgium), Judgment, I.C.J. Reports 2002, Dissenting Opinion of Judge ad hoc Van den Wyngaert, p. 137, 155.


See Dispute regarding Navigational and Related Rights (Costa Rica v. Nicaragua), Judgment, I.C.J. Reports 2009, p. 213, para. 141.


Application of the Convention on the Prevention and Punishment of the Crime of Genocide (The Gambia v. Myanmar), Provisional Measures, Order of 23 January 2020, I.C.J. Reports 2020, p. 3, paras. 37–38.


Using the same rhetoric to look beneath the legal veneer of advisory requests driven by NGO campaigns, see Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, I.C.J. Reports 1996, Separate Opinion of Judge Guillaume, p. 287, 287–288 (querying “whether, piercing the veil, the Court should not have dismissed them as inadmissible”).

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