Professional practice

Sam Wordsworth specialises in public international law and international arbitration. He is regularly instructed by Governments in international cases and has appeared before numerous international tribunals including the International Court of Justice and Tribunals constituted with respect to the Law of the Sea. He is a Visiting Professor teaching investment arbitration at Kings College, London and is regularly instructed as counsel in investment treaty disputes (he also sits as arbitrator in a limited number of disputes).

Notable cases as counsel that are in the public domain include: before the ICJ, the Ukraine v Russia case concerning alleged financing of terrorism and racial discrimination in Crimea (for Russia); the Iran v USA cases concerning Alleged violations of the 1955 Treaty of Amity and Certain Iranian Assets (for Iran); the request for an Advisory Opinion concerning the decolonisation of Mauritius (for the UK); the Bolivia v Chile case concerning the obligation to negotiate access to the Pacific Ocean (for Chile) and the Chile v Bolivia case concerning the Silala river (for Chile); Guatemala’s Territorial, Insular and Maritime Claim (for Belize); the Peru v Chile and Costa Rica v Nicaragua maritime boundary cases (for Chile, for Costa Rica); the cases concerning Certain Activities and the Road (for Costa Rica); Advisory Opinion concerning the Kosovo case (for the UK); the Diallo case (for Guinea); before the ITLOS and ad hoc tribunals, the Ukraine v Russia cases concerning Coastal State rights in the Black Sea and Detention of Naval Vessels (for Russia); the Mox plant case (for the UK), the Chagos Islands case Mauritius v UK (for the UK), the Kishenganga case (for Pakistan); before the Iran-US Claims Tribunal, Case A15 concerning Iranian property in the USA (for Iran); the European Court of Human Rights, Al-Skeini v UK, Al-Jedda v UK and Hassan v UK (for the UK), the Nada and Al Dulimi cases (for the UK); before the UK Supreme Court Serdar Mohammed (concerning legality of UK detention operations in Afghanistan), Belhaj (concerning alleged complicity of the UK in torture); before the Singapore courts: Swissbourgh Diamond Mines and others v Kingdom of Lesotho (for Lesotho).

Sam Wordsworth advises regularly on international law matters, including questions concerning treaty interpretation, international watercourses, maritime boundaries, the Law of the Sea, investment treaty disputes, State immunity, sanctions, dispute settlement procedures. He is co­author of Halsbury’s Vol. 61 “International Law and Foreign Relations” and one of the co­-authors of the forthcoming Oppenheim’s International Law 10th ed.


What others say

“A superstar.”
Chambers & Partners UK Bar 2018
International Arbitration

“Extraordinarily knowledgeable in the PIL sphere. He is very thoughtful and will engage with problems in great depth.” “A worthy opponent who has built a really impressive practice.”
Chambers & Partners UK Bar 2018
Public International Law

‘A first choice for states and investors all around the world in BIT disputes.’
Legal 500 UK Bar 2017
International Arbitration: Counsel

‘One of the very best barristers working in public international law with an excellent knowledge of the field.’
Legal 500 UK Bar 2017
Public International Law

“In investment treaty arbitration, he is one of the standouts.”
Legal 500 UK Bar 2016
International Arbitration

“States and corporations entrust him with their most important international law cases and he always delivers.”
Legal 500 UK Bar 2016
Public International Law

“His academic prowess in addition to his practical experience makes him a prototype PIL lawyer. He is the crown prince in this area.” “He’s fantastic – one of those PIL practitioners who is completely absorbed in the topic.”
Chambers UK 2015
Public International Law

“He is effective, serious and responsive.”
Chambers UK 2015
International Arbitration

Public international law

Instructed by various Governments and has appeared before the International Court of Justice and the International Tribunal for the Law of the Sea as well as various ad hoc tribunals. Cases in the public domain include:

ICJ: Guatemala’s Territorial, Insular and Maritime Claim (Guatemala/Belize): instructed by Belize

ICJ: Alleged violations of the 1955 Treaty of Amity; and Certain Iranian Assets: instructed by Iran

ICJ: Legal consequences of the separation of the Chagos Archipelago from Mauritius: instructed by UK

ICJ: Application of the International Convention for the Suppression of the Financing of Terrorism and of the International Convention on the Elimination of All Forms of Racial Discrimination (Ukraine v. Russian Federation): instructed by RF

ICJ: Status and Use of the Waters of the Silala (Chile v. Bolivia): instructed by Chile ICJ: Maritime delimitation (Costa Rica v. Nicaragua): instructed by Costa Rica

ICJ: Obligation to Negotiate Access to the Pacific Ocean (Bolivia v. Chile): instructed by Chile

ICJ: Certain Activities case; Construction of a Road case (Costa Rica v. Nicaragua, Nicaragua v. Costa Rica (for Costa Rica).

ICJ: Maritime dispute (Peru v. Chile): instructed by Chile.

ICJ: Accordance with International Law of the Unilateral Declaration of Independence of Kosovo: instructed by UK.

ICJ: Application of the International Convention on the Elimination of All Forms of Racial Discrimination (Georgia v. Russia): instructed by Russia (allegations of ethnic cleansing arising out of armed activities of August 2008).

ICJ: Aerial Incident at Lockerbie (Libya v UK): instructed by the UK Government (surrender of Libyan suspects).

ICJ: Ahmadou Sadio Diallo (Guinea v Democratic Republic of Congo): instructed by Guinea (diplomatic protection, claim of breach of shareholders’ rights and expropriation).

ICJ: Gabcikovo/Nagymaros Project (Hungary v Slovakia): instructed by Slovakia (international environmental law, necessity, law of treaties).

ICJ: Aerial Incident (Iran v USA): instructed by Iran.

Law of the Sea, Coastal State rights in the Black Sea (Ukraine v. Russian Federation) instructed by the RF.

Law of the Sea, establishment by the UK of a Marine Protected Area around the Chagos Archipelago (Mauritius v. UK) instructed by the UK.

Law of the Sea, international environmental law: Ireland v. UK (the MOX Plant case): instructed by the UK Government both before ITLOS and the Annex VII Tribunal (alleged pollution from the Sellafield site).

Law of the Sea; Barbados v. Trinidad and Tobago (maritime delimitation): instructed by Trinidad and Tobago.

Other: Iran v. USA: Case A15 (interpretation and application of Algiers Accords with respect to Iranian property in the USA): instructed by Iran.

Other: Ireland v. UK (confidentiality; access to information under Article 9 of the OSPAR Convention): instructed by the UK Government.

Other: Eurotunnel v. UK and France (concerning the Channel Tunnel) instructed by the UK Government.

Other: Pakistan v. India (Kishenganga Arbitration) instructed by Pakistan.

Other: Pakistan v. India (concerning the Baglihar hydroelectric power plant) instructed by Pakistan.

UNCC: Kuwait Airways v Iraq: instructed by Kuwait Airways.

Various cases before the ECJ, ECHR and English domestic courts, cases including:

Air Transport Association of America (and Ors) v. Secretary of State for Energy and Climate Change (CJEU, instructed by UK)

Elgafaji v. Netherlands (ECJ, instructed by UK)

Intertanko v. Secretary of State for Transport (ECJ, instructed by UK)Nada v. Switzerland (ECtHR, instructed by UK, intervening)

Al-Dulimi v. Switzerland (ECtHR, instructed by UK, intervening)

Hassan v. UK (ECtHR, instructed by UK) Al Skeini v. UK (ECtHR, instructed by UK) Al Jedda v. UK (ECtHR, instructed by UK)

Al Saadoon v. UK (ECtHR, instructed by UK)

Serdar Mohamed v. Secretary of State for Defence (legality of detention of suspected insurgents in Afghanistan)

Belhaj v. Right Hon. Jack Straw and Ors (alleged complicity in unlawful rendition and torture of Libyan nations)

Hussein v. Secretary of State for Defence (legality of UK military interrogation technique)

Equality and Human Rights Commission v. The Prime Minister and Others (legality of HMG Guidance on the Interviewing of Detainees Overseas, etc)

Al Bazzouni v. The Prime Minister and Others (legality of HMG Guidance on the Interviewing of Detainees Overseas, etc)

KTHY/CTA v. Secretary of State for Transport (legality of direct flights from UK airports to northern Cyprus)

R (Al Haq) v. Secretary of State for Foreign and Commonwealth Affairs and others (Legality of alleged UK acts in relation to Israel’s armed intervention in Gaza)

Hassan v. Secretary of State for Trade and Industry (licensing of arms for export to Israel);

Instructed by UK Government and various other States to advise on public international law matters.

Advises generally on various public and private international law issues, including maritime delimitation, environmental law issues and international watercourse law, immunities of states and heads of state, and ramifications of public international law in private law disputes and/or disputes involving one state only.

Investor-state Arbitration

Instructed as counsel on many UNCITRAL and ad hoc arbitrations, as well as in ICSID arbitrations and arbitrations before the Iran/US Claims Tribunal. Sitting as arbitrator in two ongoing ICSID cases.

Ongoing cases where instructed as counsel include: representing Pakistan in annulment proceedings (ICSID); representing India in claim concerning alleged interference with contractual rights (UNCITRAL); representing Lesotho in a treaty claim concerning alleged expropriation of mining rights (UNCITRAL), and before the Singapore courts with respect to challenge proceedings); representing Jordan in an investment treaty claim concerning an alleged denial of justice (ICSID); representing a Finnish national in a claim against Egypt (UNCITRAL); representing a UK investor in a claim against Argentina (UNCITRAL); representing Central Asian State in a case brought by a US investor (ICSID).

Past cases include: representing Deutsche Bank in its claim against India (UNICITRAL); representing Australia in its defence to Philip Morris Asia’s BIT claim concerning Australia’s legislation on plain packaging of tobacco products (UNCITRAL); Bayindir v Pakistan (ICSID); Impregilo v Pakistan (ICSID); claim against SE Asian state interfering with licenses of telecoms investor (UNCITRAL); expropriation of shipyard contracts by Central European state.

(UNCITRAL); expropriation of contractual rights of Eurotunnel (Eurotunnel v UK and France) (ad hoc); expropriation of contract rights by Asian state (UNCITRAL); US Oil Company v. Yemen (multi-billion dollar ICC arbitration, instructed by Yemen, including with reference to substantial claims for environmental damage); Basilea v. Johnson & Johnson (billion dollar claim for breach of license agreement).


2011 Attorney General’s Panel, A

2010 Professeur Invité, Université de Paris, Paris X

2009 Visiting Professor, International Commercial and Investment Treaty Arbitration, Kings College London (formerly Visiting Senior Lecturer)

1998 Essex Court Chambers

1997 Call: Lincoln’s Inn

1994 Admitted to French Bar (avocat à la cour, barreau de Paris)

1991-97 Frere Cholmeley (now Eversheds), Paris: Solicitor/Avocat.à la cour. Practice primarily in international arbitration and public international law


2000 LLM International Law (part time), LSE

1986 BA (First Class Hons in English), University College, London

Fluent French (written and oral)


1986 Morley Medal (for top first) and Ivor Evans Prize, University College, London