Sean Aughey

Professional practice

Sean’s specialises in public international law (“PIL”) before international and domestic courts and tribunals and investor-State arbitration.

Sean is recommended in the Legal Directories as a leading junior for PIL and international arbitration (Chambers and Partners (Global Guide) and Legal 500). In this year’s entries, he is described as having “an absolutely first-rate mind, excellent sense of judgement and knowledge of PIL”, being “terrific on detail”, and “very knowledgeable about public international law, rigorous in his research, and good to work with”. Who’s Who Legal adds that Sean is a “superb barrister” “who peers variously describe as ‘very able’ and ‘a great team player’” and “sources describe him as ‘clearly one of the leading juniors in international public law’”.

His recent notable instructions include three cases before the ICJ (including successfully acting for Iran in Certain Iranian Assets (Iran v USA)), three cases before investor-State arbitration tribunals (including acting as sole counsel for a State), and two key cases before the UK Supreme Court concerning the relationship between international law and English law (Rahmatullah (No. 2) v. MOD and Belhaj v. Straw).

Sean was appointed Junior Counsel to the Crown (the UK Attorney General’s Public International Law B Panel) in 2020, and he previously worked as an Assistant Legal Advisor to the UK Foreign and Commonwealth Office. He was previously appointed to the Attorney General’s PIL C Panel in 2017.

Sean’s advice on matters of public international law has been cited in national UK newspapers (see here and here in relation to the UK’s withdrawal from the EU Treaties), and he recently gave joint written evidence to the UK House of Lords (see here).

Sean previously held positions at the University of Cambridge (as a Bye Fellow in Law and supervisor in European Union law at Downing College, Cambridge in 2010-11), Harvard Law School (as a Visiting Scholar (EALS) in 2012) and Pepperdine University School of Law (as Adjunct Professor in Public International Law from 2015-17).

He is a committee member of the Administrative Law Bar Association and previously completed a traineeship at the European Court of Human Rights.

Sean recently spoke at the London Conference of International Law (2022) and co-authored an article (with Amy Sander) entitled ‘Intervention before the ICJ: A practical guide’ (2022).

He is currently writing a chapter on ‘Public International Law and Foreign Relations in Judicial Review’ for the forthcoming edition of a leading practitioners’ text on Judicial Review.

What Others Say

“A brilliant barrister and a pleasure to work with. He has skills and judgement way beyond his years.” Chambers UK, 2024, PIL
“A junior with a clear analytical eye.” Legal 500 2024, Public International Law
“He’s the brainiest person you’ll ever meet and an exceptional PIL lawyer.” Chambers UK, 2023, PIL
“He interrogates every proposition and counter until he knows he’s got the right answer – he completely bottoms everything out. He can then distil it into a calm, measured and persuasive presentation.” Chambers UK,2023, PIL
“Quite simply superb: Sean has a remarkable work ethic combined with incredible analytical powers, and an ability to retain and recall vast quantities of information. Very easy to work with: he gets to the point and is refreshingly un-flashy.” – Legal 500 2023, Public International Law
“A real star. Very bright, knows the law inside out, hard working and gets it.” – Legal 500 2023, International Arbitration
“He has a gigantic brain but is accessible and friendly. He’s responsive and likes to roll his sleeves up and get stuck into cases.” – Chambers UK 2022, PIL
“Sean is exceptional – He has a brilliant mind.” – Legal 500 2022, International Arbitration
“A great junior barrister in public international law.” – Legal 500 2022, Public International Law
“Undoubtedly the best PIL junior, he is super strong intellectually and is fully across his different spheres of knowledge within PIL.” “Very easy to work with, really hard-working and very knowledgeable.” – Chambers UK 2021, PIL (band 1)
“A really strong hands-on junior, unfazed by complex sets of facts, and with an exceptional and reliable sense of judgement, makes him all the more rare.” – Legal 500 2021, PIL (band 2)
“Superb barrister Sean Aughey who peers variously describe as ‘very able’ and ‘a great team player’. Sources describe him as ‘clearly one of the leading juniors in international public law’”. – Who’s Who Legal, Arbitration (UK Bar) 2019
“An absolutely first-rate mind, excellent sense of judgement and knowledge of PIL.” – Chambers and Partners 2020, Public International Law (Band 2)
“Terrific on detail; He thinks about things very deeply and comes up with convincing arguments.” – Chambers and Partners 2020, Public International Law (Band 2)
“Very sharp intellect.” – Chambers and Partners 2020, International Arbitration (Band 4)
“A brilliant young lawyer with an absolutely first-rate mind.” – Chambers and Partners 2020, International Arbitration (Band 4)
“Absolutely excellent – he’s got a brilliant analytic mind, he’s extremely hardworking, and a very good advocate” – Legal 500 2019, International Arbitration (Band 2)
“Very knowledgeable about public international law, rigorous in his research, and good to work with” – Legal 500 2019, Public International Law (Band 2)
“Future Leader” – Who’s Who Legal: Arbitration (Global) 2019
“A top choice for international arbitration and public international law” – Legal 500 2018, International Arbitration (Band 2)
“Absolutely fantastic for public international law” – Legal 500 2018, Public International Law (Band 3)
“Extremely creative and very international in outlook” – Chambers and Partners 2019, Public International Law (Band 3)
“Highly rated junior for state-on-state disputes, investor-state arbitration and domestic litigation involving PIL aspects”, “He is excellent”, and “He is always very responsive” – Chambers and Partners 2018, Public International Law (Band 3)
“Highly sought-after for international arbitration and public international law” – Legal 500 2017, International Arbitration (Band 2)
“He combines excellent academics with acute practical skills” – Legal 500 2017, Public International Law (Band 3)
“highly recommended” – Legal Week’s Stars at the Bar 2017
“One of the best public international law juniors at his level, possibly the best; his knowledge is unparalleled” – Legal 500 2016, Public International Law
“One of the sharpest minds at the junior end of the arbitration and public international law Bar” – Legal 500 2016, International Arbitration
“Quick to grasp the essential issues; he is destined for great things” – Legal 500 2015, Public International Law
“His skills are excellent; he is a very strong junior in the area of public international law” – Legal 500 2015, International Arbitration
His submissions are “scholarly, well researched and cogent” – UKEAT/0192/11/DA

Public international law

Sean has developed a significant and broad practice in public international law before domestic and international courts and tribunals.

Before the ICJ:

Certain Iranian Assets (Iran USA), Merits – counsel and advocate for Iran, led by Vaughan Lowe K.C. and Sam Wordsworth K.C.
Alleged Violations of the 1955 Treaty of Amity, Economic Relations, and Consular Rights (Iran v. USA), Preliminary Objections – counsel and advocate for Iran, led by Vaughan Lowe K.C. and Sam Wordsworth C.
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 Russian Federation), Preliminary Objections – counsel for Russia, led by Sam Wordsworth K.C.
Certain Iranian Assets (Iran v. USA), Preliminary Objections – counsel and advocate for Iran, led by Vaughan Lowe K.C. and Sam Wordsworth K.C., with Philippa Webb.
Alleged Violations of the 1955 Treaty of Amity, Economic Relations, and Consular Rights (Iran v. USA), Provisional Measures – counsel and advocate for Iran, led by Vaughan Lowe K.C. and Sam Wordsworth K.C., and with Philippa Webb.
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), Provisional Measures – counsel for Russia, led by Sam Wordsworth K.C.

Before the English courts:

R (Charles) v Secretary of State for Foreign and Commonwealth Affairs [2020] EWHC 3185 (Admin) – acted pro bono for the family of Harry Dunn in their judicial review challenging the FCO’s conclusion that Mrs Sacoolas was entitled to diplomatic immunity.
Lysongo v. FCO and Cameroon [2018] EWHC 2955 (QB) – acted for the FCO in securing strike out on grounds of non-justiciability of unincorporated treaties, UN immunity, state immunity, Crown act of state and foreign act of state.
Rahmatullah (No 2) v. Ministry of Defence [2017] UKSC 1 – acted for the Government Appellants in striking out tort claims challenging legality of detention of suspected insurgents in Afghanistan and Iraq on the ground of the Crown act of state doctrine. Led by James Eadie K.C., Karen Steyn K.C. and Sam Wordsworth K.C.
Belhaj v. Straw [2017] UKSC 3 – acted for the Government in its appeal on state immunity and foreign act of state. Concerned whether claims of complicity in unlawful detention and mistreatment overseas at the hands of foreign state officials are properly triable in the English courts. Sole junior led by Rory Phillips K.C., Sam Wordsworth K.C. and Karen Steyn K.C. Also instructed for the liability stage prior to settlement.
R (Bancoult) v Secretary of State for Foreign and Commonwealth Affairs (No. 3) [2013] EWHC 1502 (Admin) (inadmissibility of diplomatic documents) – advised the Secretary of State.

Before foreign courts:

Minister of Justice v. SALC, South Africa Constitutional Court – acted for Amnesty International as amicus curiae in the Al Bashir head of state immunity case concerning South Africa’s failure to arrest President Al Bashir and surrender him to the ICC. Appeal withdrawn by South Africa following its withdrawal from the Rome Statute of the ICC. Led by Sudhanshu Swaroop K.C. and with Philippa Webb.

Before other international courts and tribunals:

Advising the UK on proceedings before the Espoo Compliance Committee in relation to Hinkley Point C (led by Sam Wordsworth K.C.).
Advising the Albanian Compensation and Restitution Agency, a State entity, on the compatibility with the ECHR of Albania’s proposed new draft law on redress for mass expropriation under the former Communist regime.
Annex VII UNCLOS arbitration: Mauritius v. United Kingdom (Marine Protected Area of the British Indian Ocean Territory), assisted counsel to the UK.
ICTY (as an intern): Prosecutor v. Popovic et al (conspiracy to commit genocide), assisting counsel for the Seventh Defendant as an intern with the Defence.

Sean was a member of the Legal Panel for the Legal Report for the Inquiry on Protecting Children in Armed Conflict (under the lead authorship of Shaheed Fatima K.C.; inquiry chaired by Gordon Brown) (Hart 2018).

As a pupil to Karen Steyn (now Lady Justice Steyn), Sean assisted in many of the key cases concerning the relationship between PIL and English law, including:

R (Noor Khan) v Secretary of State for Foreign and Commonwealth Affairs [2014] EWCA Civ 24 (alleged UK liability in relation to drone strikes; foreign act of state and non- justiciability)
Haqim and others v Secretary of State for Defence (jurisdiction over and justiciability of habeas corpus applications and ECHR claims)

Before coming to the Bar, Sean interned at the boutique public international law firm Volterra Fietta, where he worked on various public international law cases and advised on a wide range of issues including boundary disputes. He was also an intern with the International Law Programme at Chatham House.

Investor-State Arbitration

Sean has considerable experience of investor-State arbitration cases, including under the ICSID Convention, the UNCITRAL Rules and the SCC Rules. He frequently works closely with law firms as part of a team of counsel and has also been instructed as sole/lead counsel.

Notable cases in the public domain include:

Bayindir v. Pakistan (No 2) – lead counsel to Pakistan in a dispute under the Pakistan-Turkey BIT relating to the consequences of Bayindir v. Pakistan (No 1).
Al-Tuwairqi v. Pakistan – sole counsel to Pakistan in a dispute under the OIC Agreement relating to the alleged expropriation of a DRI steel plant.
Tethyan Copper Company Ltd v. Pakistan, ICSID Case No. ARB/12/1 – acting for the Respondent in annulment proceedings in relation to the second largest ICSID award ever issued (led by Sam Wordsworth K.C. and with Lucas Bastin K.C.).
Al Jazeera v. Egypt, ICSID Case No. ARB/16/1 – acting for the Claimant in a dispute under a BIT regarding interference with media organisations and journalists (led by Toby Landau K.C. and with Peter Webster).
KLS Energy Lanka Sdn. Bhd v. Sri Lanka, ICSID Case No. ARB/18/39 – acting for Sri Lanka in a dispute under a BIT regarding alleged construction of a renewable energy power plant (led by Toby Landau K.C.).
Alghanim v. Jordan, ICSID Case No. ARB/13/38 (arbitration and annulment proceedings) – successfully acted for Jordan in a dispute under a BIT regarding taxation of a telecommunications investor (led by Sam Wordsworth K.C. and with Lucas Bastin K.C.).
Kingdom of Lesotho v. Swissbourgh Diamond Mines [2018] SGCA 81 – acting for Lesotho before the Singapore High Court and Court of Appeal (non-admitted) with respect to proceedings challenging an arbitral award rendered by an investor-State tribunal concerning alleged expropriation of mining rights arising from Lesotho’s participation in the decision- making of an international organisation (led by Sam Wordsworth K.C.).
Josias Van Zyl and others v. Kingdom of Lesotho, PCA Case No. 2016-21 (Second Case) – successfully acted for Lesotho in obtaining termination of proceedings (led by Sam Wordsworth K.C.).
PL Holdings v. Poland – successfully acting for the Claimant in a dispute under an intra-EU BIT and the SCC Rules concerning the expropriation of a bank (led by Stephen Fietta).

Before coming to the Bar, Sean interned at the boutique public international law firm Volterra Fietta and worked on various investor-State cases, including successfully acting for the Claimant in Karmer v. Georgia, ICSID Case No. ARB/08/19, a dispute under a BIT regarding interference with construction hospitality projects. He also interned at Wilmer Hale’s international arbitration practice.

Sean has participated in successful bids for appointment to panels of counsel eligible to represent India and Romania in investor-State arbitration disputes.

His advisory work includes issues of investment protection, treaty interpretation, dispute settlement and enforcement of investor-State arbitration awards and immunities.

Bayindir v. Pakistan (No 2) – lead counsel to Pakistan in a dispute under the Pakistan-Turkey BIT relating to the consequences of Bayindir v. Pakistan (No 1).
Al-Tuwairqi v. Pakistan – sole counsel to Pakistan in a dispute under the OIC Agreement relating to the alleged expropriation of a DRI steel plant.
Tethyan Copper Company Ltd v. Pakistan, ICSID Case No. ARB/12/1 – acting for the Respondent in annulment proceedings in relation to the second largest ICSID award ever issued (led by Sam Wordsworth K.C. and with Lucas Bastin).
Al Jazeera v. Egypt, ICSID Case No. ARB/16/1 – acting for the Claimant in a dispute under a BIT regarding interference with media organisations and journalists (led by Toby LandauK.C. and with Peter Webster).
KLS Energy Lanka Sdn. Bhd v. Sri Lanka, ICSID Case No. ARB/18/39 – acting for Sri Lanka in a dispute under a BIT regarding alleged construction of a renewable energy power plant (led by Toby Landau K.C.).
Alghanim v. Jordan, ICSID Case No. ARB/13/38 (arbitration and annulment proceedings) – successfully acted for Jordan in a dispute under a BIT regarding taxation of a telecommunications investor (led by Sam Wordsworth K.C. and with Lucas Bastin).
Kingdom of Lesotho v. Swissbourgh Diamond Mines [2018] SGCA 81 – acting for Lesotho before the Singapore High Court and Court of Appeal (non-admitted) with respect to proceedings challenging an arbitral award rendered by an investor-State tribunal concerning alleged expropriation of mining rights arising from Lesotho’s participation in the decision- making of an international organisation (led by Sam Wordsworth K.C.).
Josias Van Zyl and others v. Kingdom of Lesotho, PCA Case No. 2016-21 (Second Case)– successfully acted for Lesotho in obtaining termination of proceedings (led by Sam Wordsworth K.C.).
PL Holdings v. Poland – successfully acting for the Claimant in a dispute under an intra-EU BIT and the SCC Rules concerning the expropriation of a bank (led by Stephen Fietta).

Before coming to the Bar, Sean interned at the boutique public international law firm Volterra Fietta and worked on various investor-State cases, including successfully acting for the Claimant in Karmer v. Georgia, ICSID Case No. ARB/08/19, a dispute under a BIT regarding interference with construction hospitality projects. He also interned at Wilmer Hale’s international arbitration practice.

Sean has participated in successful bids for appointment to panels of counsel eligible to represent India and Romania in investor-State arbitration disputes.

His advisory work includes issues of investment protection, treaty interpretation, dispute settlement and enforcement of investor-State arbitration awards and immunities.

Sean is a member of the team analysing the jurisdictional decisions of investor-State arbitration tribunals for InvestmentClaims.com, a leading OUP database. He was previously an editor of the Young ICCA blog.

Career

2020: Appointed to the Attorney General’s B PIL Panel

2017: Appointed to the Attorney General’s C PIL Panel

2015-17: Adjunct Professor in Public International Law, Pepperdine University, London

2011: Stagiaire, European Court of Human Rights

2011: Intern, Volterra Fietta

2011: Intern, International Arbitration Department, Wilmer Hale

2010-11: Bye-Fellow in Law and supervisor in European Union Law, Downing College, University of Cambridge

2010: Intern, International Law Programme, Chatham House

2010: Volunteer, Advice and Information Department, Liberty

2010: Call: Lincoln’s Inn

2009: Intern, International Criminal Tribunal for the Former Yugoslavia

Education

2012: Harvard Law School, Visiting Scholar (EALS)

2010: Bar Vocational Course, BPP: Very Competent

2009: The Hague Academy of International Law, Public International Law Session

2009: University of Cambridge, Downing College, LL.M: Class I (ranked second overall)

Settlement of International Disputes – highest mark in the year
International Human Rights – highest mark in the year
International Commercial Litigation – joint highest mark in the year

2008: University of Cambridge, Downing College, BA (Hons), Law Tripos

Awards

2011: Grant to undertake traineeship at the ECtHR in Strasbourg, Lincoln’s Inn

2010: Grant to participate in the international rounds of the Jessup International Law Mooting Competition, Lincoln’s Inn.

2009: Lord Denning Scholarship, Lincoln’s Inn; Hardwicke Award, Lincoln’s Inn.

2009: International Law Fund Scholarship, Lauterpacht Centre of International Law; Association Prize, Downing College; Harris Prize for Especial Distinction (top 2.5% of class list), Downing College

2007: Buchanan Prize, Downing College; Graystone Prize, Downing College; Harris Scholar and Senior Harris Scholar, Downing College; Rebecca Flower Squire Scholarship, University of Cambridge

Publications and Talks

‘Public international law and foreign relations in judicial review’, chapter in second edition of Auburn, Moffett and Sharland, Judicial Review, 2nd ed, (OUP) (not yet published).
Article 30 of the Vienna Convention on the Law of Treaties, forthcoming chapter in M Waibel and A Kulick, General International Law in Investment Law: A Commentary (not yet published).
‘Formation and development of customary international law in times of emergency’, London Conference of International Law, October 2022.
Member of the Legal Panel for the Legal Report for the Inquiry on Protecting Children in Armed Conflict (under the lead authorship of Shaheed Fatima K.C.) (Hart 2018).
Cross-examination in international arbitration, Young ICCA and CEPANI40 skills training workshop, Brussels, 14 September 2018.
‘Act of state is dead; long live act of state’, Lauterpacht Centre of International Law, 16 February 2018.
‘Armed Drones and Judicial Review’, PLP Judicial Review Conference, October 2016. ‘When should there be a duty to investigate UK military action abroad?’, Public Law Project conference on Inquiries, Investigations and the Law, 21 April 2016.
‘Uses and Abuses of Unincorporated Treaties’, Administrative Law Bar Association, 2 February 2016.
‘Recent Developments: International Law in the UK Courts’, Government Legal Service International Law Conference, 14 October 2015.
‘International Law in Domestic Courts’, lecture presented to the Government Legal Service’s inaugural International Law Course, 9 June 2015.
‘Targeting and Detention in Non-International Armed Conflict: Serdar Mohammed and the Limits of Human Rights Convergence’, 91 International Law Studies (2015) 60-118 (with Sari).
Several short pieces on EJIL:Talk!, the Blog of the European Journal of International Law.
‘Foreign employees’, chapter in Tolley’s Employment Law Handbook (2015-18).

Barrister at Essex Court Chambers

Professional practice