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 by the Hellenic Republic to address its financial crisis.  In an award issued on April 9, 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.

  • The Hellenic Republic in an ICSID arbitration brought by Cyprus Popular Bank Public Co. Ltd for alleged violations of the Hellenic Republic-Cyprus bilateral investment treaty concerning measures taken by the Hellenic Republic to address its financial crisis.

  • 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 May 2014 for lack of jurisdiction or on the merits.

  • The Arab Republic of Egypt in an 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.

  • The Republic of Iraq in an ICC arbitration against the Republic of Turkey and its State-owned pipeline company BOTAŞ for breaches of intergovernmental agreements on the use and operation of transnational oil pipelines and a 1946 Mutual Friendship Treaty in connection with the use of the pipeline and related facilities to transport, store and load crude oil extracted from the Kurdistan region.

  • The Republic of Austria in an ICSID arbitration commenced under Austria-Malta bilateral investment treaty concerning an investment in an Austrian bank.

  • OJSC Tatneft in an UNCITRAL arbitration under the Russia-Ukraine bilateral investment treaty arising out of a raider takeover of the largest refinery in Ukraine. The tribunal rejected all of Ukraine’s jurisdictional and admissibility objections and awarded damages.

  • DP World in an 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.  The claims totaled more than US$100 billion and are thought to be the largest arbitrations in amount in dispute.

  • 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 alleges that the purchase price involved State aid in violation of EU competition law.

  • OAO Gazprom in an UNCITRAL arbitration against the Republic of Lithuania under the Russia-Lithuania bilateral investment treaty concerning the forced divestiture of the natural gas transmission operations and assets of AB Lietuvos Dujos, the largest integrated natural gas distribution company in Lithuania.  OAO Gazprom was a shareholder in AB Lietuvos Dujos.

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Selected Activities

  • Adjunct Professor, University of Vienna
  • Visiting Professor, Paris West University Nanterre
  • Member, Court of Arbitration of the Singapore International Arbitration Centre
  • 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.


  • Role of Investor’s Legitimate Expectations’ In Defense of Investment Treaty Claims, Yearbook on International Investment Law & Policy 2013-2014
  • “Investment Treaty Arbitration as a Tool to ‘Enforce’ Arbitral Awards?, The European Middle Eastern and African Arbitration Review 2015
  • “Protection of Sovereign Wealth (book review),” ICSID Review (April 15, 2014).
  • “Protection and Admission of Sovereign Investment under Investment Treaties,” Chinese Journal of International Law, Volume 10 (2011).
  • “How Bilateral Investment Treaties Can Protect Foreign Investors in the Arab World or Arab Investors Abroad,” Journal of International Arbitration, Volume 25, N°2 (2008).
  • “State Succession and the Liquidation of a UK Licensed Bank,” Banker’s Law, Volume 1, N°4 (2007).
  • “How Better Investment Treaties May Help China Investors,” IFLR (March 2006)
  • “State Immunity and Arbitration”, ICC International Court of Arbitration Bulletin, Volume 15, N° 2 (Fall 2004).
  • “How Bilateral Investment Treaties Can Protect Japanese Investors,” Journal of the Japanese Institute of International Business Law (2004).
  • “Free Movement of Goods and the Protection of Trademarks – Current Issues concerning Repackaging, Relabelling and Rebranding in EC law,” The Journal of World Intellectual Property, Volume 5 (2002).
  • “Die Rechtswirkungen von Sicherheitsratsresolutionen im österreichischen Recht,” (“The Legal Effects of UN Security Council Resolutions in Austrian Law”) Juristische Blätter (1995).
  • “Die Inexistenz als Angriffs- und Verteidigungsmittel vor dem EuGH und EuG,” (“Inexistent Legal Acts in Proceedings before the European Courts”) Europäische Zeitschrift für Wirtschaftsrecht, Volume 2 (1995).
  • “Part Two of the International Law Commission’s Draft Articles on State Responsibility,” German Yearbook of International Law, Volume 37 (1994).
  • “The Legal Régime of Erga Omnes Obligations in International Law,” Austrian Journal of Public International Law, Volume 46, No. 2 (1994).


  • October 20, 2017: “Session two: The GAR Live symposium” at the GAR Live Vienna Conference.
  • 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 05, 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.