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Sub practice
Sub practice

Public International Law and Investment Treaty Disputes

Allen & Overy’s specialist Public International Law team acts for corporations, financial institutions, international organisations, governments and States in all aspects of contentious and non-contentious public international law matters, including investment disputes. 

Our market leading practice combines expertise in issues such as title to natural resources, state responsibility and succession, boundary disputes, investment treaty arbitration, trade law and sanctions.

A&O’s advisory work spans the full range of public international law issues, including:

  • drafting and negotiation of international treaties and conventions
  • investment protection measures
  • international sanctions regimes
  • privileges of international organisations and state immunity
  • recognition of states and state succession
  • human rights
  • trade law

On the contentious side, we have a pre-eminent investment treaty arbitration practice acting for investors and sovereign States. We have advised on more than 70 investment treaty disputes and a number of ICSID annulment proceedings, and are one of only a handful of law firms to have experience of WTO disputes.

We advise on State-to-State disputes arising under public international law and team members have acted as counsel before international courts and special tribunals, and have also advised States on out-of-court strategies for dispute resolution.

Our experience includes advising:

  • A State on its negotiation with the European Union in relation to a comprehensive free trade agreement.
  • A Middle Eastern State on the potential reform of its investment treaties. 
  • The investment arm of a Middle Eastern State in relation to a draft bilateral investment treaty being negotiated with a South American State, and on how best to structure new investment acquisitions in that State.
  • Over 30 different international investors, in 12 separate ECT claims (all claims bar one brought at ICSID) against the Kingdom of Spain. The claims relate to investments made in the Spanish renewable energy sector, and retrospective changes by Spain to the regulatory framework. These cases include the first-ever collective, or aggregated, claim brought under the ECT. We have so far achieved significant damages awards for our clients in six of these arbitrations, with others still pending.
  • The Islamic Republic of Pakistan in two related claims, brought under the UNCITRAL Rules, arising from alleged interference in gas import operations at a port terminal. The Tribunal dismissed the nearly USD600m claims in their entirety and ordered the claimants to pay nearly 90% of Pakistan’s costs. We successfully defeated challenges to the Award, made by the claimants, in the English courts.

Awards and achievements

  1. Tier One, Public International Law, Legal 500 UK 2019
  2. Band 1, Dispute Resolution, Global-wide, Chambers Global 2019
  3. International Arbitration Firm of the Year, Benchmark Litigation Asia-Pacific Awards 2019
  4. Best Arbitration Team of the Year in Spain and Portugal, 2019 


News & insights

Image of Kate Davies McGill

News: 22 December 2021

Allen & Overy arbitration partner Kate Davies McGill appointed QC

Allen & Overy’s Kate Davies McGill has been appointed Queen’s Counsel in the 2021 competition.

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Allen & Overy ranked third worldwide for "Global Leaders" in Who's Who Legal Arbitration 2022

News: 09 December 2021

Allen & Overy third worldwide - Who's Who Legal: Arbitration 2022

The Who’s Who Legal: Arbitration 2022 survey of the world’s leading arbitration lawyers lists 16 Allen & Overy lawyers as “Global Leaders”, placing A&O third in the global rankings in terms of…

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spiral staircase

Publications: 10 November 2021

Enforcement of arbitration awards against States – court documents must be served through diplomatic channels

In General Dynamics v Libya [2021] UKSC 22, the UK Supreme Court confirmed that diplomatic service of court documents on a State’s Ministry of Foreign Affairs is mandatory when enforcing an arbitral…

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Aerial photo of a busy city street with people on zebra crossing

Publications: 01 November 2021

Court of Justice of the European Union says ad hoc submission to arbitration of dispute between EU Member State and EU investor under BIT is against EU law

On 26 October 2021, the Court of Justice of the European Union (the Court) delivered its judgment in Case C‑109/20, Republic of Poland v PL Holdings S.á r.l. (PL Holdings).

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