An arbitrator’s prior participation in a similar dispute is one of the most frequently invoked bases for issue-conflict challenges. It is also one of the most difficult to establish. Arbitrators are expected to apply the law consistently, and the mere fact that an arbitrator has previously decided the same legal question does not mean that the arbitrator has prejudged a new case.
The risk becomes more serious where the new dispute substantially replicates the earlier one: the same or closely related parties, the same legal issues, materially overlapping facts, and potentially the same evidence or witnesses. In those circumstances, the concern is not only a previously expressed legal opinion but also the arbitrator’s prior exposure to a factual record that may influence the new proceeding.
The “Triple Identity” Approach
A useful analytical framework emerging from the cases is to examine three forms of identity or overlap:
- identity or close connection between the parties;
- identity of the legal issue or applicable legal framework; and
- identity or substantial overlap of the material facts and evidence.
The test is not a rigid rule of law. It is better understood as a way to assess how likely it is that the arbitrator’s prior participation will affect the current case. The greater the cumulative overlap, the stronger the argument that a reasonable observer may perceive prejudgment.
Caratube: The Leading Successful Challenge
Caratube v. Kazakhstan is the strongest example of a successful challenge based on prior participation in a highly similar dispute. Arbitrator Bruno Boesch had previously sat in Ruby Roz Agricol v. Kazakhstan. The cases involved the same respondent, closely related claimants, similar facts and overlapping evidence, including witnesses likely to testify in both proceedings.
The unchallenged arbitrators considered the prior factual knowledge relevant to the pending case and upheld the challenge. The decision is significant because the analysis was not based merely on the arbitrator having taken a legal position before. The factual overlap was extensive enough that prior exposure to the earlier case itself became part of the concern.
Practical point. Caratube shows why factual identity often matters more than the abstract similarity of legal questions. The closer the two evidentiary records are, the harder it becomes to treat the cases as genuinely independent exercises.
Belokon: Similar Law Without Similar Facts Was Insufficient
Belokon provides a useful contrast. Professor Kaj Hober had participated in another case in which denial of justice was discussed and Kazakhstan was the respondent. The challenge failed because the factual circumstances were not sufficiently similar. The shared legal concept and overlap in the respondent did not establish that the arbitrator had prejudged the distinct dispute before him.
The decision illustrates the danger of defining the alleged issue too broadly. Legal concepts such as denial of justice, expropriation, necessity or fair and equitable treatment arise in many cases. A challenge should identify the specific proposition and explain why the factual context of the prior case makes the arbitrator’s earlier reasoning relevant to the present dispute.
Tidewater: Parallel Proceedings and the Importance of the Applicable Standard
In Tidewater v. Venezuela, Professor Brigitte Stern was sitting simultaneously in another case involving Venezuela and a similar jurisdictional question under Venezuelan investment legislation. The challenge also relied on multiple appointments. Nevertheless, it was dismissed.
The case demonstrates that substantial overlap does not guarantee success. The tribunal emphasised that the arbitrator could consider the issue de novo and was not legally bound by the outcome of the other proceeding. The decision has also been discussed as an example of the importance of the disqualification standard applied in ICSID cases.
Majority Decisions, Dissents and Separate Opinions
A prior view may be expressed through a majority award, a dissenting opinion, a separate opinion or questioning during a hearing. The cases suggest that the formal vehicle is less important than the substance and the degree of overlap. A dissent does not automatically demonstrate stronger personal commitment than participation in a majority award, and neither form is automatically disqualifying.
Challenges involving James Spigelman and Gary Born illustrate this point. The fact that an arbitrator previously joined a majority or wrote a dissent was not sufficient where the broader circumstances did not establish the required appearance of prejudgment.
The 2024 IBA Guidelines
The 2024 IBA Orange List expressly addresses related prior or current proceedings. Item 3.1.5 covers an arbitrator who currently serves, or has served within the past three years, as arbitrator or counsel in another arbitration on a related issue or matter involving one of the parties or an affiliate. The provision is a useful reference point but is not a substitute for analysing the actual degree of overlap.
The 2024 Guidelines also clarify that the Application Lists are non-exhaustive and that the General Standards prevail. A situation outside Item 3.1.5 can still create justifiable doubts, while a listed situation does not automatically require disqualification.
How to Assess a Prior-Case Challenge
- Identify the exact issue allegedly decided in advance.
- Compare the parties and corporate or factual relationships between them.
- Compare the treaty, contract, legislation or other legal provisions at issue.
- Map the factual allegations and evidence in both proceedings.
- Identify common witnesses, experts, documents or factual findings.
- Assess whether the arbitrator had access to confidential information in the earlier proceeding that may be relevant in the new case.
- Determine whether the earlier decision contains a categorical view or leaves room for factual or legal distinction.
- Consider additional circumstances, such as repeated appointments, writings or overlapping professional roles, but do not treat them as substitutes for the core issue-conflict analysis.
Commercial Arbitration
The same reasoning is applicable in international commercial arbitration, although published examples are less common because commercial proceedings are generally less transparent. Earlier French cases show that prior participation in connected construction disputes can raise similar concerns. In specialised industries, recurring facts and a limited pool of arbitrators can make these questions particularly important.
Conclusion
Prior decisions do not disqualify an arbitrator simply because they show a legal view. The more persuasive issue-conflict cases demonstrate a meaningful combination of party connection, legal identity and factual overlap. Caratube remains the clearest illustration: the prior case was sufficiently similar that the arbitrator’s earlier exposure to facts and evidence created an objective concern. By contrast, where only a general legal concept or one element of similarity is present, challenges usually fail.
Selected authorities
- Caratube International Oil Company LLP and Devincci Salah Hourani v. Kazakhstan (II), ICSID Case No. ARB/13/13, Decision on Disqualification (20 March 2014).
- Valeri Belokon v. Kyrgyz Republic, PCA Case No. AA518, Decision on Challenges (6 October 2014).
- Tidewater Investment Srl and Tidewater Caribe, C.C. v. Venezuela, ICSID Case No. ARB/10/5, Decision on Challenge (23 December 2010).
- Sapec, S.A. v. Kingdom of Spain, ICSID Case No. ARB/19/23, Decision on Disqualification of James Spigelman (25 June 2020).
- KS Invest GmbH and TLS Invest GmbH v. Kingdom of Spain, ICSID Case No. ARB/15/25, Decision on Disqualification of Gary Born (30 April 2018).
