The context: an advanced stage of a broader reform
On 15 April 2026, the UNCITRAL Secretariat published draft supplementary provisions (“SPs”) on the conduct of proceedings in investor–State disputes, intended for consideration at the Commission’s June–July 2026 session with a view to finalisation.1
The draft outlines three possible implementation routes, each requiring party consent: as a protocol to the multilateral instrument on ISDS reform (alongside structural reforms such as a potential investment court); as an annex to the UNCITRAL Arbitration Rules (“the Rules“); or as standalone provisions applicable across arbitral frameworks, subject to party agreement on a rule of conflict i.e. where the SPs and institutional rules are inconsistent.
Although implementation will take time and the text may still evolve slightly, the SPs represent an advanced stage in UNCITRAL’s ISDS reform process, ongoing since 2017. That process has already produced instruments such as mediation guidelines and codes of conduct for arbitrators and judges. The SPs now focus on harmonising procedural practice.
Overall, they codify and structure tribunal discretion, introduce clearer time limits (including for awards and termination), and set out mechanisms such as for consolidation. They also impose constraints in sensitive areas, notably public interest and costs. The SPs broadly align with the 2022 ICSID Arbitration Rules—particularly on early dismissal, case management and third‑party funding disclosure. Their adoption is therefore likely to reinforce procedural convergence across ISDS regimes, reducing fragmentation rather than creating a competing system.
The Draft Supplementary Provisions
Evidence : This SP builds on arts. 27 and 30 of the UNCITRAL Rules while introducing additional guidance. It preserves tribunal discretion to dispense with document production, even if requested by one party. At the same time, it provides structured criteria for deciding whether to order production over objection, including the request’s scope, timeliness, relevance, materiality, and the burden of production, as well as the basis for objection. The SP also sets out express grounds for excluding evidence, including where it was obtained unlawfully, is fraudulent or fabricated, or is inadmissible under applicable law or privilege rules. Finally, tribunals are expressly empowered to conduct site visits or inquiries connected to the dispute, either at a party’s request or on their own initiative, subject to the parties’ right to participate.
Early case management tools :2
- Bifurcation – a party may request that an issue, including jurisdiction or quantum, be addressed in a separate phase of the proceeding. Relevant circumstances that the Tribunal must consider include whether bifurcating would reduce time and cost, dispose of all or a substantial portion of the claim or be impractical due to the issues to be addressed separately being so intertwined.
- Manifest lack of legal merit of claim – a party may make this objection within 60 days of the Tribunal’s constitution. The objection can relate to the substance of the claim or the Tribunal’s jurisdiction. It does not include defences due to a concern that this would create overlapping, simultaneous procedural tracks which would be cumbersome in the same arbitration.
Interim measures : this SP largely mirrors art. 26 of the Rules but differs by a) removing from the list of examples of interim measures that of providing “a means of preserving assets out of which a subsequent award may be satisfied”; and b) stating expressly that the Tribunal shall not grant an interim measure which interferes with the challenged State act or (as marked for consideration by the Commission) which “impedes a State’s right to regulate in the public interest, including in order to protect life, health or environment”.
Costs and funding discipline :
- Security for costs order – the considerations that a Tribunal must consider are the usual ones – ability and willingness to comply, its effect on the relevant party’s ability to bring the claim, and party conduct – but also the existence of third-party funding. A point to be decided by the Commission is whether the funder’s willingness to pay an adverse costs order (which the funded party is required to disclose) should also be one of the factors that the Tribunal should consider and, if so, to what extent this should influence the Tribunal’s discretion in granting the order .
- Costs allocation – the loser pays principle is applied as per art. 42 of the Rules but specific considerations for determining apportionment, where the Tribunal considers it reasonable, are given: outcome, conduct, complexity, reasonableness of costs (including the difference between the costs claimed by each party) and the amounts claimed versus the amounts awarded. Success fees and costs incurred by a funded party due to the funding arrangement are expressly excluded from costs allocation.
- Third-party funding – provision is made for disclosure of such funding, with failure to comply potentially leading to costs consequences.
Suspension of the proceeding : the Tribunal shall suspend the proceeding when jointly requested by the parties and, subject to the applicable rules, may do so at the request of one of the parties or on the Tribunal’s own initiative.
Termination of the proceeding : the Tribunal can order the same on joint request of the parties; no step being taken by the parties in 180 days (grounds which are additional to art. 36 of the Rules); or if the continuation of the proceeding becomes unnecessary or impossible.
Period of time for making the award : from the date of the last submission, this shall, barring special circumstances, be no later than 60 days (regarding an objection that the claim is manifestly without legal merit), 180 days (regarding a separate phase of the proceeding following bifurcation) and or 240 days (in all other cases).
Consolidation and coordination: consolidation combines related arbitrations so a single tribunal resolves them, potentially through one or more awards. Coordination, by contrast, aligns selected procedural steps across parallel proceedings while preserving their separate identity and resulting in distinct awards. Under the draft SPs, parties to multiple arbitrations may jointly propose consolidation or coordination terms and consult tribunals and any administering institutions to ensure feasibility. If appropriate, tribunals then issue implementing orders. While party consent has always permitted both approaches in practice, the SPs introduce a clearer, structured framework for proposing, assessing and operationalising them.