The New Wave of Article 63 Interventions at the International Court of Justice

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Recent developments in the Ukraine v. Russia case at the International Court of Justice may force the Court to address head-on an important point of procedure relating to intervention pursuant to Article 63 of the Court’s Statute.

The Court’s Statute in Articles 62 and 63 provides two separate devices to States wishing to intervene. In general terms, both are incidental proceedings, governed by largely uniform procedures under Articles 81-86 of the Rules of Court.  Neither requires the consent of the parties to the case, but both require the third-party State to establish a form of legal interest in the case: under Article 62 this is a particular ‘interest of a legal nature which may be affected by the decision in the case’ and in respect of Article 63 it is simply that the intervening State be a party to a convention that must be interpreted by the Court. If a State intervenes as a non-party pursuant to Article 62 the judgment may take its interests into account but will not bind the intervening State. Article 63 intervention, on the other hand, results in a judgment that binds parties and intervenors alike.

On 21 July 2022, Latvia filed their Article 63 declarations of intervention, followed by Lithuania on 22 July 2022, New Zealand on 28 July 2022 and the United Kingdom on 5 August 2022. However, Ukraine is not scheduled to file its Memorial until 23 September 2022, while Russia’s Counter-Memorial isn’t due until 23 March 2023. Despite Russia’s non-appearance at the provisional measures hearings, the Russian Ambassador has informed the Court that future participation in the proceedings is ‘still under consideration’. This suggests that a Preliminary Objections application by Russia could be on the cards.

If so, the Court will be forced to confront the question of whether or not other States may intervene in a case at the jurisdictional stage, whether to argue that the Court is jurisdictionally competent to proceed or to deny it. The Court has faced this issue once before, in Military and Paramilitary Activities in and against Nicaragua, when it rejected El Salvador’s attempted intervention as premature.

This post will review the Court’s Article 63 practice and reflect on the possibility of a new direction in the Court’s jurisprudence.

Article 63: A Brief Review

Article 63 states that:

  1. Whenever the construction of a convention to which states other than those concerned in the case are parties is in question, the Registrar shall notify all such states forthwith.
  2. Every state so notified has the right to intervene in the proceedings; but if it uses this right, the construction given by the judgment will be equally binding upon it.

Article 63 grants a right to States to intervene in a contentious case when they are party to a multilateral treaty that will be interpreted in the Court’s judgment. This right is, however, subject to the Court’s power to declare the intervention inadmissible.

While intervention is a common procedure in domestic courts, when delegates of the first Peace Conference met in The Hague in 1899 it was entirely unknown to the history of international dispute resolution, which had an exclusively arbitral character. Dutch jurist TMC Asser proposed to incorporate an intervention procedure during the fourth meeting of the 1899 Comité d’Examen, in terms that underwent only slight changes before being eventually adapted into the PCIJ and ICJ Statutes as Article 63. The most notable change was the removal of a statement that the Court’s judgment is only binding on the parties, a proviso now found separately in Article 59 of the Court’s Statute. 

It is often asserted that the object of Article 63 was to acknowledge the ‘res interpretata effect’ (Miron & Chinkin, 2019) of the Court’s judgments. The intervenor is bound by the interpretation that the Court gives to the relevant convention, vis-à-vis the original parties to the case, and also presumably in respect of other States should it become involved in a different dispute involving the interpretation or application of the same treaty.  It would be rare but not inconceivable that the Court would apply a different interpretation in such a situation (as distinct from a different application to the relevant facts) although this has never been tested. 

The only case of intervention before the PCIJ, the SS Wimbledon, was pursued under Article 63. A claim was brought by Great Britain, France, Italy, and Japan against Germany in relation to its refusal to permit access to the Kiel Canal.  It was alleged that German authorities had prevented the British steamship SS Wimbledon, chartered by the French armament firm Les Affréteurs réunis, from passing through the canal. Although Italy and Japan had suffered no direct harm, the PCIJ observed that:

each of the four Applicant Powers has a clear interest in the execution of the provisions relating to the Kiel Canal, since they all possess fleets and merchant vessels flying their respective flags.

The PCIJ accepted that the applicant States shared ‘a recognized interest in ensuring compliance with the international regime’ established by Article 380 of the 1919 Versailles Peace Treaty.   Poland ‘declared itself in agreement with the submissions of the applicants.’  The approach of the PCIJ in the SS Wimbledon reveals a shared understanding that an intervenor under Article 63 can come in support of one of the original parties. 

The Court has continued to take the view that intervention to support a party’s particular interpretation of the relevant treaty is permissible. In the most recent intervention admitted under Article 63, that of New Zealand in Whaling in the Antarctic, the Court confirmed that Article 63 interventions ‘cannot affect the equality of the parties to the dispute’, because the intervener cannot acquire the status of a party.  Japan’s contention that Australia and New Zealand were, for all intents and purposes, parties in the same interest ‘pursuing what may in effect be a joint case’ received minimal attention.

The Issue of Timing

However, while Lithuania, Latvia, New Zealand, and the UK may come in support of Ukraine’s position on the merits, that is not the only question before the Court in the present case. There is also the issue of timing. That is, whether States can intervene in a case pursuant to Article 63 before the Court has concluded that it has jurisdiction to proceed to the merits.

In Military and Paramilitary Activities in and against Nicaragua, the Court decided to reject El Salvador’s Article 63 declaration on the basis that application was untimely for being made in the jurisdictional phase of the proceedings.  The Court noted that El Salvador’s declaration ‘presuppose[d] that the Court had jurisdiction to entertain the dispute’. However, El Salvador was not granted an opportunity to defend its application at an oral hearing. Nicaragua did not formally object to the intervention, although it drew the Court’s attention to ‘certain deficiencies both in form and substance’ – an objection de facto if not de jure. Nevertheless, the lack of a formal objection meant that El Salvador had no right to a hearing under Article 84(2) of the Rules. Judges Ruda, Ago, Mosler, Jennings, and Lacharriere jointly opined that it would have been ‘more in accordance with judicial propriety’ for an oral hearing to have taken place.  Having been denied the opportunity to participate at all, the Court nevertheless relied on information provided by El Salvador’s declaration of intervention during the merits phase of the case.

Addressing El Salvador

Three of the four intervenors have been careful to address the issue of timing head on. Scholarly opinion has been fairly well unanimous that there is no reason, based on the text of the Statute, not to allow Article 63 intervention for the purposes of challenging or supporting jurisdiction, or arguing for a different construction of a treaty’s compromissory clause altogether. Lithuania has argued that ‘Article 63 is unqualified as far as the type of provisions of the convention – substantive, procedural or jurisdictional – is concerned.’ The UK has argued that ‘[t]here is no limitation in Article 63 … that would prevent the United Kingdom from exercising its right to intervene on the construction of provisions of the Genocide Convention pertaining to issues of jurisdiction in addition to issues pertaining to the merits.’ The UK also considers the different scenarios that would result if the Court decides to separate the question of jurisdiction from the question of the merits, pursuant to the recently amended Rules of Court. Latvia, meanwhile, takes the El Salvador precedent head on and argues that ‘neither the Court nor Judges writing individually in that case suggested that Article 63 could not, in principle, apply to jurisdictional issues.’

Only New Zealand has not mentioned the issue of timing, save that the construction of the Genocide Convention for which they contend is ‘relevant to both the Court’s jurisdiction and to the substantive basis of Ukraine’s claims on the merits.’ As pointed out by Ori Pomson on Twitter, however, New Zealand’s declaration only puts forward ‘(very) abstract’ constructions of the Genocide Convention, as opposed to the significantly more forceful submissions of the other States.


It remains to be seen how the Court will deal with these interventions. Two things are worth noting. First, Russia could attempt to replicate Nicaragua’s litigation strategy and deny the intervenors a hearing, which could impact negatively on the proper administration of justice. Second, the only precedent the Court has is one in which it denied the right of intervention at the jurisdictional stage. It remains unclear whether the decision holds for intervention at the jurisdictional phase generally or can be distinguished on the facts on the basis that it was a conclusion that ‘the particular claim belonged more accurately in the merits phase’ (Chinkin, 1986).

It is worth noting also that this is not the only case where Article 63 interventions will be an issue. In the other genocide case presently before the Court, The Gambia v. Myanmar, The Maldives, Canada and the Netherlands have indicated their intention to act as intervenors in the case, which could only be on the basis of Article 63. However, the particular question of timing discussed in this post will not be an issue, as the Court has already handed down its decision on jurisdiction.

Those interested in questions of procedure should keep a close eye on both cases, as they will contribute to a sudden expansion in the Court’s Article 63 practice and may help to further clarify the Court’s views on the function and purpose of intervention.

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Juliette McIntyre says

August 16, 2022

A minor correction on the dates. Those in the post are the dates the documents were signed. The declarations were *filed* on 21 July Latvia, 22 July Lithuania, 28 July NZ, and 5 August UK.

Andreas Zimmermann says

August 16, 2022

Dear colleague,
thanks for this interesting post.
It ought be mentioned though that in light of information made available by the Ukrainian MFA online (see Ukraine seems to have filed its memorial in the case on July 1, which means that the three months period for eventually filing preliminary objections provided for in Art. 79bis para 1 Rules of Court started running at this point already.
Andreas Zimmermann

Brian McGarry says

August 16, 2022

Thanks for bringing further attention to this topic, Juliette.

Re:"The UK also considers the different scenarios that would result if the Court decides to separate the question of jurisdiction from the question of the merits, pursuant to the recently amended Rules of Court", you may be interested in a post I wrote for this blog in May, which laid out the significance of such a caveat:

Kind regards,

Arman Sarvarian says

August 16, 2022

Dear Juliette,

Thank you for this interesting post. It may be of interest that the ILA Committee on the Procedure of International Courts and Tribunals looked at the question of timing for Article 63 interventions at pages 11-12 of its final report, albeit from the perspective of delay to the proceedings rather than a premature declaration. The Committee suggested that '[t]he time-limit for the filing of Article 63 declarations could also be aligned with the Counter-Memorial rather than the opening date of the headings, thereby providing more time to parties to incorporate the pleadings of Article 63 intervenors into their oral arguments.'

What do you consider to be the considerations for the 'proper administration of justice' for Article 63 intervention at the jurisdictional phase versus the merits phase, assuming proceedings to be bifurcated?

Juliette McIntyre says

August 17, 2022

Arman, thanks so much for your comment - I have read the Report with great interest. In my personal opinion, the suggestion regarding CMs is a good one as a general practice. It's important to ensure that the respondent State isn't placed at a significant disadvantage, particularly where the intervenors all come in support of the applicant. Additionally, however, Art 63 intervenors should be permitted to make submissions if they are relevant to jurisdiction. How to address bifurcation? One option would be the Court electing not to bifurcate where intervenors are making submissions on both jurisdicton and the merits - this avoids two long hearings with multiple parties. Where intervenors are concerned only with the issue of jurisdiction, bifurcation poses no hazards. In general, I think the Court can play a more active case management role and should do so in these kinds of cases.