An annulment decision rendered in favor of Spain last June has been creating headlines in international arbitration. The International Centre for Settlement of Investment Disputes (ICSID) annulled an award for the first time based on the ground of the arbitrator’s lack of independence and impartiality in the Eiser Infrastructure and Energia Solar Luxembourg Sarl v Kingdom of Spain case 1 (“Eiser case”). The Eiser case stands out as a crucial case as it deals with the much-debated issue of the conflict of interest (between an arbitrator and an expert) in investment arbitration. Acting as counsel for Spain, Curtis Mallet-Prevost Colt & Mosle reaffirmed itself as a go-to counsel for governments and state-owned entities, with expertise in handling high profile cases shaping international arbitration.

This month, Jus Mundi is pleased to put a spotlight on Curtis and its team, with exclusive insight on the team’s arbitration strategies to win cases in light of the COVID19.

Key facts of the Eiser case and legal rationale

(a) the Tribunal was not properly constituted;

(b) the Tribunal manifestly exceeded its powers;

(c) there was a serious departure from a fundamental rule of procedure;

(d) the award failed to state the reasons on which it was based.

  • Spain contended that the lack of impartiality and independence of an arbitrator renders the Tribunal’s constitution improper and warrants the annulment of the award.
  • Spain further defended that it could raise such an issue because the facts upon which its argument is based became known after the award was rendered. In this case, Spain should not have been considered as having waived its right to raise such allegations.
  • Lastly, it was argued that, in the present case, such “manifest appearance of bias” stems from the longstanding relationship between Dr. Alexandrov and Eiser’s (the investor) expert witness, the Brattle Group, as well as the failure to disclose the said relationship. Spain submitted that, during Dr. Alexandrov’s time as a partner at Sidley Austin in Washington, DC, Alexandrov’s team had appointed the Brattle Group in nine investor-state arbitrations. Four out of nine cases included Lapuerta as the testifying expert, with some cases still pending during the Eiser arbitration.
  • On June 11th, 2020, a committee chaired by Ricardo Ramírez-Hernández (Mexico) alongside Makhdoom Ali Khan (Pakistan) and Dominique Hascher (France) annulled the award in its entirety, on two of the four grounds invoked by Spain’s counsel. The panel first recognized arbitrator Stanimir Alexandrov’s failure to disclose the professional relationship with one of the investor’s expert witnesses. This failure to disclose led the committee to observe an improper constitution of the Tribunal. Secondly, recognizing that the failure to disclose such information could have had a “material effect” on the award, the committee characterized a serious departure from a fundamental rule of procedure.

In the annulment proceeding, the leading law firm Curtis Mallet-Prevost Colt & Mosle in New York, Mexico and Washington, DC, and the in-house team of Abogacía General del Estado defended Spain. Curtis’s team included renowned partners Benard Preziosi (New York), Arianna Sánchez (New York), Gabriela Alvarez-Avila (Mexico City), Claudia Frutos-Peterson (Washington, DC) and associate Ricardo Mier y Teran (Mexico City).

Interview with Gabriela Alvarez-Avila and Claudia Frutos-Peterson

1. What challenges did you face in the course of the annulment of the Eiser award?

As you may know, we were not counsel of record during the arbitration proceedings. We therefore needed to familiarize ourselves in a short period of time with the case docket in order to assess the Award properly and identify the grounds for annulment to be included in the Application for Annulment. We were lucky to work with the Abogacia del Estado in the annulment proceedings, which sped up the process of familiarizing ourselves with the docket and they worked with us to identify the problems with the Award.  Although we felt strongly regarding the grounds to annul the Award, some of the grounds for annulment (i.e. the improper constitution of the Arbitral Tribunal and the serious departure of a fundamental rule of procedure) became apparent later on, specifically after the conflict of interest between one of the arbitrators and the claimants’ expert (who were acting in a separate case) was contested by Pakistan in August 2017 in the Tethyan Copper case.

2. What impact do you think the Eiser case will have on the future of international arbitration?

There is no doubt that the Eiser annulment decision is a very timely precedent in investment arbitration, particularly in light of ongoing discussions between States and the investment arbitration community with regards to conflicts of interest and the need for an arbitrators’ code of conduct in investment arbitration. The Eiser annulment decision confirms that: a) relationships with experts matter and need to be disclosed; b) lawyers who have an extensive practice as counsel and arbitrator (i.e. “double-hatting”) in investment arbitration need to be particularly careful and make disclosures in a timely manner; and c) under the ground of improper constitution of the tribunal, the requesting party can raise challenges to an arbitrator that could not have been raised during the course of the arbitration proceedings because the conflict was not known at the time.

3. Curtis has built a strong portfolio of clients including several States. What do you think makes the firm one of the prime choices for States?

Curtis exclusively represents States in investment arbitrations. This internal policy guarantees to States that we do not have conflicts of interest or that we will be raising arguments that could be used against us later down the line when defending States.  Our arbitration team is composed of lawyers from different background and jurisdictions, which allows us to serve our State clients better as we are fully able to understand their needs and legal traditions. We also have an incredible success rate for our State clients of approximately 86%, which obviously makes Curtis the best choice.

Moreover Curtis arbitration team has defended States in some of the biggest claims in investment  arbitration, which raised extremely complex issues, and in cases where novel issues under public international  law have been discussed.  In both instances, Curtis has obtained excellent results for its State clients.

4.  How did you and your colleagues in the arbitration team adapt to the online hearings and other case strategies in the times of COVID19?

Our arbitration team has already performed a number of virtual hearings, which have gone very smoothly. However, COVID19 times can be more challenging for some of our State clients and we hope that tribunals will make the appropriate accommodations. In particular, for some of the complex cases that we handle, it is evident that virtual hearings will present difficulties for guaranteeing equal and fair treatment for both parties.

Presentation of the law firm

Curtis’ caseload has included many of the world’s best-known arbitrations and over US$100 billion in claims. George Kahale III leads the arbitration practice. The firm has acted in several of the world’s most famous investment and commercial arbitrations and ad hoc arbitrations under the UNCITRAL rules. Curtis’ attorneys bring decades of experience in representing clients involved in complex commercial arbitrations and frequently representing clients in arbitrations under a wide range of international arbitration rules. Their clients range from sovereigns and sovereign-owned entities to Fortune 500 companies, startups, and individuals across the main business sectors.

Recognized as a leading law firm in the world for high-stake international arbitration, the firm stands out by the number of sovereign representations at ICSID and its outstanding international arbitration team.  Key clients of Curtis include India, Venezuela, Cyprus, Indonesia, Kazakhstan, Spain, Libya, National Oil Corporation of Libya, Uganda, Kuwait, Albpetrol Sh.A., Ghana National Petroleum Corporation, Saudi Arabia, Czechia, Romania, Mellitah Oil & Gas B.V., Vietnam, Russia, the United Nations, , Nigeria, Philippines, Dominican Republic, Ecuador.

Curtis also has a Public International Law practice and is one of the few law firms to act as Counsel before the International Court of Justice (ICJ). Tullio Treves (Milan) has acted before the ICJ as Counsel for Finland in the Great Belt case and for Peru in the maritime dispute with Chile.

For more information, please visit

The annulment of the Eiser case is not the only time Curtis has secured victory for its client. Check out the interactive table of cases below to learn about the other instances in which Curtis has won or currently representing.

Table of arbitration cases involving Curtis (Recent victories/pending cases)*

Currently, Curtis is acting as counsel in several ICSID cases, notably in the annulment proceedings for Venezuela against ConocoPhillips (ConocoPhillips v. Venezuela), for Kuwait against Almasryia (Almasryia for Operating & Maintaining Touristic Construction Co. L.L.C. v. State of Kuwait).

To see all types of cases (investor-state, inter-state, commercial arbitration) involving Curtis available on Jus Mundi, please click here.

Curtis earns its spot to be the ATOM for its extensive track-record of arbitration cases & clients. We selected a few recent victories and ongoing cases in the table below.

(Note*: This table is not exhaustive and only includes the most famous cases)


No.Year CaseInstitutionTypeRoleStatusTeam
1.2020Eiser and Energía Solar v. SpainICSIDInvestor-StateCounsel for the StateDecided in favor of the State
(Annulment proceedings)
New York, Washington, London, Mexico City
2.2020Gold Pool v. Kazakhstan PCAInvestor-StateCounsel for the StateDecided in favor of the State New York, Milan, Washington
3.2019Churchill Mining and Planet Mining v. IndonesiaICSIDInvestor-StateCounsel for the StateDecided in favor of the State
(Initial Award and Annulment proceedings)
New York, Washington, London
4.2019Almasryia for Operating v. KuwaitICSIDInvestor-StateCounsel for the StateDecided in favor of the State
(Annulment proceedings ongoing)
London, Mexico City
5.2020Adamakopoulos and others v. CyprusICSIDInvestor-StateCounsel for the StatePendingNew York, Washington
6.2020ConocoPhillips v. VenezuelaICSIDInvestor-StateCounsel for the StatePendingNew York, Mexico City, Buenos Aires, Milan, Paris
7.2019Caratube v. Kazakhstan (II)ICSIDInvestor-StateCounsel for the StateDecided in favor of the investorNew York, Washington, Mexico City, Buenos Aires
8.2018Tidewater v. VenezuelaICSIDInvestor-StateCounsel for the StatePartial Annulment granted in favor of the StateNew York, Mexico City
9.2018Mobil and others v. VenezuelaICSIDInvestor-StateCounsel for the StatePending (Resubmission)New York, Mexico City
10.2015Dunkwa Continental v. GhanaICCCommercial Arbitration Counsel for the RespondentConcluded in favor of the RespondentNew York, London


Spotlight: The Eiser annulment team

Partner operating in the New York and Washington offices, Benard has extensive experience as lead counsel in international arbitration cases, mostly in defense of sovereign states and state-owned entities. Benard is considered a core member of the teams representing States in high profile cases, including ConocoPhillips Petrozuata et al. v Venezuela (ICSID) and Dunkwa v Ghana (ICC).

Arianna is a partner in the New York office and has been involved in a wide range of complex investor-state disputes, representing governments and state-owned entities in Europe, the Middle East, and Latin America. She has also acted as counsel in high-valued international commercial arbitrations under the ICC and the LCIA. Alongside Benard, Arianna was notably part of the Curtis team that secured one of the largest ICSID annulment award of US$1.4 billion to date in Mobil and others v. Venezuela.

Gabriela is a partner in the Mexico City office and has acted as counsel for foreign states in investor-state and commercial arbitrations and was appointed as arbitrator in commercial arbitrations under the ICC Rules and the arbitration rules of the Centro de Arbitraje de México (CAM). Gabriela was part of the Curtis team that defended Kuwait in its successful application of ICSID Arbitration Rule 41(5) that dismissed Almasryia’s claims for lack of merit. Mexico has also designated her to the ICSID Panel of Arbitrators. Before joining Curtis, Gabriela was a counsel with ICSID, where she administered arbitrations as secretary of tribunals. Gabriela has been consistently recognized by Chambers Latin America, Chambers Global and Legal 500 as a leading lawyer in international arbitration and dispute resolution, is named a leading figure in the Mexican arbitration market by Who’s Who Legal and is ranked in the Latinvex list of Latin America’s top 100 Female Lawyers.

Claudia is managing partner in the Washington office and former counsel at ICSID. Her practice focuses on arbitration, international law, and international investment law as a representative of governments and state entities. Claudia was part of the Curtis team that defended Indonesia in a billion-dollar mining claim brought by Churchill Mining, successfully dismissing all claims against its clients in 2016, and subsequently securing a decisive victory again in the annulment hearing in 2019. Claudia has also acted as counsel for private companies in international commercial arbitrations under the SIAC and the ICC. Mexico has also designated her to the ICSID Panel of Arbitrators. Claudia has also been appointed in the List of Arbitrators of Centro de Conciliación y Arbitraje de Panamá and AmCham, Perú.  She has acted as an arbitrator in several commercial arbitration cases.  Claudia has been ranked by Chambers USA and Legal 500 as a leading international arbitration lawyer nationwide and recognized by Chambers Latin America and Chambers Global for international arbitration Latin America-wide. She is ranked in the Latinvex list of Latin America’s top 100 Female Lawyers and has been recognized by Who’s Who Legal since 2016.

Ricardo is an associate in the Mexico City office, where he focuses his practice on investor-state and international commercial arbitration under the ICSID, ICC, LCIA, the Inter-American Commercial Arbitration Commission (IACAC) and CAM rules. He has been involved in proceedings related to oil and gas, shareholder disputes, and in claims related to the energy and construction industries.


 For more information on Curtis’ International Arbitration practice, click here.


Congratulations to the team again for being the ATOM, and good luck for the upcoming cases!




  1. Eiser Infrastructure Limited (UK) and Energia Solar Luxembourg Sarl v Kingdom of Spain, ICSID Case No. ARB/13/36