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Mr. Jaroslavsky Pablo

Associate, International Arbitration - Dechamps International Law

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Amici Curiae in Investment Arbitration

I. Definition


The term amicus curiae (plural: amici curiae) is the Latin translation for “friend of the court.”1 In international investment arbitration, an amicus curiae (sometimes referred to as “non-disputing party”) is any third party that intervenes in certain degree in the proceedings with the view of assisting the arbitral tribunal regarding some of the aspects of a case.2 However, allowing written submissions from an amicus curiae is not equivalent to “making that person a party to the arbitration”.3

II. Types of participation


Different persons and entities have requested arbitral tribunals to allow their participation as amici curiae in order to:

  1. obtain access to certain documents of the case;4
  2. participate in or attend to oral hearings;5 and
  3. make written submissions.6

Yet, in those cases in which tribunals have accepted the participation of amici curiae, they have mostly authorized the filing of written submissions and, on occasions, expressly limiting their scope.7 


On the other hand, tribunals have generally rejected amici curiae’s requests to obtain access to the documents of the case,8 although some tribunals have exceptionally accepted this kind of petitions.9 


In the same vein, tribunals have also generally refused to allow amici curiae to participate in or attend to oral hearings,10 although there is a precedent in which a petition of this nature was granted.11

III. Source of the arbitral tribunals' powers to accept amici curiae's participation


Arbitral tribunals have found their power to accept amicus curiae’s participation in different instruments and rules, such as:

  1. The North America Free Trade Agreement (“NAFTA”) Free Trade Commission’s Statement on non-disputing party participation of 2003 (the “FTC Statement”).12
  2. Article 15(1) of the 1976 UNCITRAL Arbitration Rules.13 Prior to the FTC Statement, NAFTA tribunals held that neither NAFTA Chapter Eleven nor the 1976 UNCITRAL Arbitration Rules expressly allowed or prohibited tribunals to accept amici curiae submissions.14 Those tribunals considered that their power to accept such submissions could be inferred from their general procedural powers under Article 15(1) of the 1976 UNCITRAL Arbitration Rules15 (which however did not allow a tribunal to: (i) add disputing parties to the arbitration; (ii) accord them the substantive rights of a disputing party or a NAFTA member State; or (iii) broaden the subject matter of the arbitration).16 
  3. Article 44 of the ICSID Convention,17 before the amendment of ICSID’s Arbitration Rules and the entry into force of their Article 37(2) in 2006.
  4. Article 37(2) of the 2006 ICSID Arbitration Rules18 and article 67 of the 2022 ICSID Arbitration Rules.
  5. Article 41(2) of the 2006 ICSID Additional Facility Arbitration Rules19 and article 77 of the 2022 ICSID Additional Facility Arbitration Rules.
  6. Other treaties and rules.20
  7. Other tribunals’ practice, including WTO panels and the Iran-U.S. Claims Tribunal.21

IV. Conditions to allow amici curiae's participation


The FTC Statement and the ICSID Arbitration Rules (under which the vast majority of the decisions on the participation of amici curiae was rendered) allow amici curiae’s participation only under certain conditions. Article 37(2) of the ICSID Arbitration Rules, Article 41(2) of the ICSID Arbitration (Additional Facility) Rules and Point B.6 of the FTC Statement share most of these conditions,22 which are:

  1. The non-disputing party submission must assist the arbitral tribunal in the determination of a factual or legal issue related to the proceedings by bringing a perspective, particular knowledge or insight that is different from that of the disputing parties;
  2. The non-disputing party submission must address matters within the scope of the dispute; and
  3. The non-disputing party must have a significant interest in the arbitration.23

The 2022 ICSID Arbitration Rules and Arbitration Additional Facility Rules add two additional circumstances that arbitral tribunals should consider:24

  1. the identity, activities, organization and ownership of the non-disputing party, including any direct or indirect affiliation between the non-disputing party, a party or a non-disputing Treaty Party; and
  2. whether any person or entity will provide the non-disputing party with financial or other assistance to file the submission.

Additionally, the FTC Statement requires that there is a public interest in the subject-matter of the arbitration.25


Although these rules provide a useful guidance to arbitral tribunals regarding the conditions amici curiae’s participation must fulfil, investment tribunals have followed different approaches towards the issue and considered that the criteria set out in the FTC Statement are not exhaustive.26 In the end, as shown below, the issue remains, essentially, a factual one, whose assessment must be analysed in the circumstances of each case.

V. Investment tribunals' considerations to admit amici curiae's interventions


To date, 94 petitions to participate as amici curiae were made on 76 different cases (25 in NAFTA cases27 and 69 in non-NAFTA cases28). Of these, 56 petitions were fully accepted (59 per cent),29 four were partially accepted,30 and 34 were rejected by the arbitral tribunals.31 One tribunal has solicited amici curiae participation on its own initiative.32


When tribunals have accepted amici curiae’s participation, they have done it mainly based on the following considerations:

  1. the petition addressed matters within the scope of the dispute;33
  2. the petition did not unduly burden nor unfairly prejudice a disputing party’s submission or disrupt the proceedings;34
  3. the petitioner had a different expertise, experience or perspective from that of the parties that could assist the tribunal;35
  4. the petitioner had a significant interest in the arbitration;36
  5. there was a public interest in the subject-matter of the arbitration;37
  6. the petitioner was independent from the parties of the arbitration;38 and/or
  7. the petitioner provided a written undertaking that it would bear any costs arising from its intervention.39

On the other hand, tribunals have rejected petitions on the following bases:

  1. the petition addressed a matter outside the scope of the dispute;40
  2. admitting the petition would have imposed an unduly and potentially prejudicial burden on the parties in case it had been accepted;41
  3. the petitioner lacked a different expertise, experience or perspective from that of the parties that could have assisted the tribunal;42
  4. the petitioner lacked a significant interest in the arbitration;43
  5. the petitioner failed to explain the public interest it was seeking to address;44
  6. the petitioner failed to provide the tribunal with sufficient information regarding its petition;45
  7. there were doubts as to the petitioner’s independence from the parties;46
  8. the absence of the parties’ consent;47
  9. the petitioner failed to provide a written undertaking to pay any additional costs incurred by the parties in responding to its submission;48
  10. the petitioner was not a person from one of the parties to the applicable treaty nor had any significant presence in its territory;49 and/or
  11. the tribunal considered that the petition was premature.50