I have always found the submission of expert legal opinions on matters of international law to investment treaty tribunals rather odd.  Why are expert opinions needed and what is their status?  To begin, the opinion is submitted to an international arbitration tribunal often comprising leading public international lawyers (and sometimes current or former judges of the International Court of Justice).  This tribunal’s role is to interpret and apply the international investment agreement in question in accordance with public international law.  Further, an international tribunal operating under public international law is deemed to know the law (jura novit curia).  Next, we have the counsel for the claimant or respondent who submits the expert opinion, eminent international arbitration practitioners often with substantial academic and practical experience in public international law.  Then we have the the opinion, written by the expert in public international law, typically a professor or long-standing practitioner.

The practice is rather strange given the usual allocation of roles in dispute settlement: witnesses provided evidence; experts opine on technical issues or facts; and counsel make legal submissions based on the applicable law.  Yet, many of the expert legal opinions on international law that parties have submitted to tribunals in investment treaty arbitrations (see here) are used by counsel as legal submission in everything but name.

The Interim Awards on Jurisdiction and Admissibility in the Yukos cases (PCA Case Nos. AA 226, 227 and 228) present rather striking examples of this phenomenon.  The awards present a veritable battle of international law experts on issues that, based on the summaries of the expert opinions in the awards, involve legal analysis of matters of pure public international law (i.e. matter for legal submission).  Yet, at points in the awards, expert opinions are referred to as “evidence”, an expert statement as “testimony” and experts are included under the heading of “witnesses”.

This terminological blurring is probably harmless and, given the difficulty of the issues addressed in the awards, it would be petty to criticize the tribunal or counsel.  Indeed, in the Yukos cases, the parties submitted a veritable cornucopia of 23 different witness statements and expert legal opinions, which addressed a range of issues—factual statements with respects to the travaux préparatoires of the Energy Charter Treaty, statements of national law, opinions on the implementation of treaties within national legal systems and opinions more generally on the application of the Energy Charter Treaty.  Given this overlapping mélange, it is understandable there was some blurring of distinctions.

More generally, what objection can there be if a party, wishing to ensure that its legal submissions have more gravitas, chooses to support them by relying on an expert legal opinion, rather than bringing on the expert as co-counsel in the case?  Further, not all counsel and not all arbitrators are experts in public international law.  Expert legal opinions can serve an important function in ensuring that relevant legal principles are fully briefed.

Although there may be no principled objection to the use of expert legal opinions, as investment treaty jurisprudence develops and matures, I think we can expect less reliance on the expert legal opinion on international law. With the exception of the Yukos case, it may be that trend has already begun (and, in any event, the expert legal opinion on international law only appears in a minority of cases). In the future, counsel in investment treaty arbitrations will presumably do what counsel in most legal systems do—brief the law and make legal submissions without submitting opinions from legal experts.


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  1. A very interesting post. One thing that occurs to me is that an additional factor is the ability for the other side to cross-examine a legal expert. This clearly is not available in relation to legal submissions. Whether tribunals find this of assistance or not is not apparent, but it might well be a factor in the decision to submit the opinion as an expert opinion rather than to use the expert as co-counsel.

  2. I was thinking yesterday on the status of expert legal opinions in international arbitration when, contemplating a case, I found several of the world best known professors and practitioners that sustained opposite expert reports. The contradiction between them shocks, as apparently they are both highly experienced and respected. Of course they can have different views, as it is clear from their reports, but totally opposite? If the question presented to the experts was the color of the paper in front of them, they have answered not only black and white. For me, one answered “two” and the other answered “house”. So I wonder: What are we talking about? Expert reports?

    The problem of the contradiction of the expert report occurs continuously in the evaluation of the compensation or damages to be awarded to one of the parties. Using different methods and sometimes using the same discount cash flow method, one expert arrives at 5 million, the other expert at 500. Both make logical presentations of their evaluation, but is it possible or even tolerable those distant results? Use certain number, certain variables and conditions and put them into an equation, the slightest mistake can give an enormous difference. Maths.

    What about questions of public international law? What about question as for example stabilization or renegotiation clauses in BIT or in international contracts. Difficult but not mathematics. Are contradictory reports tolerable? Tolerance of course but aren’t experts supposed to be impartial (and independent) from the parties as is the case of the members of the arbitral tribunal? (Which also involves a party appointed arbitrator that was contacted by the party at an initial phase). I see expert reports that are totally biased to arrive at one solution, mentioning or focusing in certain specific point that will favor the party that appointed them and not even mentioning other points that should be at least mentioned if such extensive development was given to the previous party-favoring point. Are we supposed to accept the omission of an expert? Are we supposed to make all expert reports a fiction? C. Jarrosson wrote this even of the whole system developing around the arbitration and the quantity of show-off photo seminars; I see it in the witness statement written by the counsel and only signed by the witness –but fortunately the option of cross-examination is still opened as mentioned in the previous comment-. I am not against arbitration seminars which develop the knowledge on arbitration itself (although I would like them to be cheaper and accessible not only if you are paid a certainly high amount of Euros.) Luckily I assisted to a high quality conference (free entrance also) last Wednesday organized by the Comité français de l’arbitrage, in which Monsieur Loquin excellent exposition was highly debated at the end by judges and practitioners. Some common agreement was found in that the obligation of concentration of means and demands was not related to the fiction of res iudicata of a case, but rather to the obligation of loyalty and good faith. It only relates to the present comment regarding to the fiction that I state is present in some expert reports (not all I hope.) Even more, expert reports sometimes do not state the source when citing a document (even if in the hundred of publications the expert quotes its sources) or includes different language throughout the report when talking about the same thing. Basic issues.

    A solution. It should be better if parties agreed in a list of subjects to be submitted to the experts for a report. In this case, aren’t they submitting the dispute to arbitration for this precise reason? Having in mind that the arbitral tribunal may not constituted by experts on public international law (or other more specific subject in which expert reports could be more helpful, actually to give light to the tribunal to see and understand) asking for an expert report and presenting it should be useful. Instead of the party presenting the report with its Memorial (and having the chance to read the report, choose if they want to presented according to the degree of obedience shown by the expert, and cite it in their memorial) why not having the party willing to have an expert report inform the Tribunal on the subject of a future expert report and the candidate to make that report. After contradiction and approval in a procedural order, the party itself can contact the expert which shall provide its report stating when the party first contacted him (should be after approval by the Tribunal) and showing the questions in which the report should be based (stating that no other direction or order was given by the party). Once the report is made, it should be presented directly by the expert to the arbitral tribunal. Total impartiality (I should think) and independence from the party asking the experts legal opinion. If one of the parties is willing to ask for an expert report to demonstrate a point of law or of the arbitration, it should ask the report having in mind that the answer may not favor it. That would be more useful than having arbitrations with a bunch of tailor-made expert reports which are contradictory between them.

  3. A inconsistency of different experts views happens in valuing compensation for damages to be awarded to one of the parties. Using different methods and sometimes using the same discount cash flow method, one expert gives a figure £1,000,000 the other expert at £500. Both make logical presentations of their evaluation, but is it possible or even fair those distant results? Use certain number, certain variables and conditions and put them into an equation, the slightest mistake can give an enormous difference.

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