Claudia Annacker’s practice focuses on international litigation and arbitration and public international law matters, including investor-state disputes, disputes involving international organizations, state succession issues and state immunity, as well as disputes before the European Court of Human Rights.

Claudia joined the firm in 1998, became counsel in 2005, and became a partner in 2009. From 1998 to 2001, she was resident in the Brussels office, and from 2001 to 2004 in the New York office.

Notable Experience

  • The Hellenic Republic in an ICSID arbitration commenced by Poštová banka a.s., a Slovak bank that purchased interests in Greek Government bonds, and its Cypriot shareholder, Istrokapital SE, under the Hellenic Republic-Slovak Republic and the Hellenic Republic-Cyprus bilateral investment treaties, challenging measures taken to address the Hellenic Republic’s financial crisis.  In an award issued in April 2015, the tribunal dismissed all claims for lack of jurisdiction, holding that sovereign bonds and interests therein are not investments protected under the applicable investment treaties and that Istrokapital could not base jurisdiction on Poštová banka’s assets.  A challenge of the award was dismissed in September 2016.

  • The Republic of Austria in an ICSID arbitration commenced under the Austria-Malta bilateral investment treaty concerning regulatory measures taken against an Austrian bank and its management.  All claims were dismissed for lack of jurisdiction in October 2017.

  • The Hellenic Republic in two separate ongoing ICSID arbitrations commenced by Cyprus Popular Bank Public Co. Ltd and Bank of Cyprus Public Co. Ltd under the Cyprus-Hellenic Republic bilateral investment treaty concerning measures taken to address the Hellenic Republic’s financial crisis.

  • The Republic of Côte d’Ivoire in an ongoing ICSID arbitration commenced by Wise Solutions CDI, SA arising out of a dispute related to a concession contract for waste management services in Abidjan.

  • The Arab Republic of Egypt in an ICSID arbitration commenced by H&H Enterprises Investments, Inc. under the US-Egypt bilateral investment treaty relating to an investment in a tourist resort. All claims were dismissed in 2014 for lack of jurisdiction or on the merits.

  • The Republic of Iraq in an ongoing ICC arbitration against the Republic of Turkey for breaches of intergovernmental agreements governing the operation of transnational oil pipelines in connection with the use of the pipeline and related facilities to transport, store and load crude oil extracted from the Kurdistan region.

  • The Arab Republic of Egypt in an ongoing ICSID arbitration commenced by Unión Fenosa Gas under the Spain-Egypt bilateral investment treaty concerning the suspension of gas supplies to an LNG plant in Egypt.

  • OJSC Tatneft in an UNCITRAL arbitration brought against Ukraine under the Russia-Ukraine bilateral investment treaty. Successful award of damages in 2014. In 2016, the Paris Court of Appeals denied Ukraine's request to annul the award, and in 2017, the French Supreme Court upheld that decision.

  • The Republic of Tatarstan and its Ministry of Land Property Relations in an ongoing UNCITRAL arbitration against Ukraine under the Russia-Ukraine bilateral investment treaty. The claims arise out of a raider takeover of one of the largest refineries in Ukraine, which before the raid was controlled by Tatarstan interests.

  • DP World in an ongoing ICSID arbitration against the Republic of Peru under a concession agreement for the development and operation of the South Pier of the Port of Callao and the UK-Peru bilateral investment treaty concerning DP World’s exclusion from the tender for the North Pier concession and the tender’s structure and design.

  • The Russian Federation in three parallel UNCITRAL arbitrations under the Energy Charter Treaty commenced by one Isle of Man and two Cypriot companies, in their capacities as former majority shareholders of Yukos Oil Company, and ensuing annulment proceedings before the Hague District Court. In April 2016, the Hague District Court annulled the awards, totaling more than US$50 billion, for lack of jurisdiction.

  • Électricité de France (EDF) in defending an ICC arbitration initiated by the Federal State of Baden-Württemberg, through a special purpose company, which had acquired EDF’s shareholding in the German energy company Energie Baden-Württemberg AG (EnBW).  Claimant alleged that the purchase price involved State aid in violation of EU competition law. All claims were dismissed in 2016.

  • OAO Gazprom in an UNCITRAL arbitration brought against the Republic of Lithuania under the Russia-Lithuania BIT concerning the forced divestiture of AB Lietuvos Dujos' natural gas transmission operations and assets.

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Selected Activities

  • Adjunct Professor, University of Vienna
  • Member, Board of the Vienna International Arbitration Centre
  • Member, Court of Arbitration of the Singapore International Arbitration Centre
  • Visiting Professor, Paris West University Nanterre
  • Visiting Professor, National University of Singapore
  • Member, International Law Association
  • Member, German Society of International Law
  • Member, European Society of International Law
  • Member, American Society of International Law



  • Der fehlerhafte Rechtsakt im Gemeinschafts- und Unionsrecht (Defective Legal Acts in EU Law) (1999), Vienna/New York.
  • Die Durchsetzung von Erga Omnes Verpflichtungen vor dem Internationalen Gerichtshof (The Enforcement of Erga Omnes Obligations Before the International Court of Justice) (1994) Hamburg.



  • February 7, 2020: “Clear Path or Jungle in Commercial Arbitrators’ Conflicts of Interest?,” ASA Annual Conference, Zurich
  • December 11, 2019: “The Boundaries of Investment Arbitration,” London
  • May 16, 2019:“Evolution Of Investment Law In Treaty Making And Arbitral Practice, Comment from Counsel´s Perspective,” 10 Year Anniversary Conference Of The International Investment Law Centre Cologne, Cologne
  • May 7, 2019: “30 Years of Investment Treaty Arbitration: An Engine for the Development of General International Law for Good and for Bad,” Geneva Center for International Dispute Settlement, Geneva
  • September 20, 2018: “Recent Trends in Investment Arbitration,” AILA Investment Treaty Law and Arbitration Training, London
  • March 24, 2018: “Transforming Institutions in Investor-State Dispute Settlement,” Harvard Law School
  • October 26, 2017: “Denial of Benefits: When - How - Effects?” presentation at the 7th Investment Treaty Arbitration Conference in Prague hosted by the Minister of Finance of the Czech Republic in Prague. 
  • October 20, 2017: Co-Chair and speaker at GAR Live Vienna.
  • October 18, 2017: “Parallel Proceedings in Investment Arbitration” presentation at the 2nd UNCITRAL Asia Pacific Judicial Conference on International Law in Hong Kong, during Hong Kong Arbitration Week.
  • June 17, 2017: “Investment Protection Charter Standards under the Energy Charter Treaty, is there a need to clarify,” presentation at the International Energy Charter Forum in Brussels.
  • May 25, 2016 : “Forging the Path in Asia: The Draft SIAC Rules on Investment Arbitration,” presentation at the SIAC Congress 2016 in Singapore.
  • April 27, 2015: Chaired the panel “The reaction to contemporary jurisprudence—time to move from hegemony and fragmentation to harmonization?” at the GAR Live BITs Conference, Washington, D.C.
  • June 5, 2014: Chaired the panel “Are contracting parties successfully clawing back investment treaty protections?” at the GAR Live Frankfurt Conference.
  • March 18, 2014: “Utilization of Investment Treaties to Compel or Effectively Reverse the Enforcement of Commercial Awards: can investment treaty protections provide a second bite at the enforcement apple?” presentation at the Columbia Arbitration Day Conference, New York.
  • May 10, 2013: “Legitimate Expectations,” speech at the British Institute of International and Comparative Law’s Twentieth Public Meeting of the Investment Treaty Forum.
  • April 17, 2012: “European Civil Procedure and Arbitration,” speech at the 2012 Vienna Arbitration Days.
  • April 12, 2012: “Corruption, Fraud, and Illegality Issues in Investment Arbitration—‘Como Espada y Escudo’,” speech at the Yale Law School—Latin American Legal Studies Breakfast Roundtable.
  • November 1, 2011: “Investment Treaty Arbitration from the Perspective of the Host State,” presentation at the Meeting of the Asian African Legal Consultative Organization, “Promoting International Law,” United Nations, New York.
  • May 22, 2009: “Recent Trends in Investment Treaty Arbitration: Policy Implications—Host States’ Perspectives,” Seoul National University for International Economic and Business Law, Seoul.