T: +44 (0) 20 7831 4445
About us
Areas of practice
Instructing us
Complaints proceedure
Useful links
Established practitioners
Contact us
Call me
Back to home

Simon Olleson (PDF)

Year of Call: 2002
Education: B.A. (Hons) (Cantab); LL.M. (NYU); Dip. Int. Law. (Cantab)
Languages: Italian (fluent); French (fluent); German (basic)

Areas of practice

Simon specializes in public international law; his practice includes advice and advocacy in relation to traditional inter-State disputes (including before the International Court of Justice), investment protection disputes, international human rights law, issues of sovereign immunity, State succession and the law of the sea, as well as litigation before the English courts involving issues of public international law.

Simon has appeared as counsel before the International Court of Justice, as well as before arbitral tribunals operating under the auspices of the International Centre for the Settlement of Investment Disputes and the Permanent Court of Arbitration. He has also acted as secretary or clerk to the tribunal in a number of international investment protection disputes, as well as acting as clerk to the tribunal in a multi-million dollar commercial arbitration in relation to a failed tourism infrastructure project.

Simon is recommended as a Leading Junior (Band 3) for Public International Law in Chambers and Partners UK 2016 where he is described as having "a strong PIL practice spanning inter-state disputes, investment treaty arbitrations, Law of the Sea and state immunity issues", and as being "superb at getting things done in a timely way and good with demanding clients".

He has previously been recommended in Chambers and Partners UK since 2008: described variously "fantastic", as having "a practice that spans the full spectrum of the field" and an "in-depth understanding of matters concerning state responsibility", and as being "an experienced performer in international human rights and environmental law" (Chambers 2015); as having a "serious practice in the field", as being a "good all-round general international lawyer" and "clear and level-headed", and having a "wealth of knowledge of investor-State arbitrations" (Chambers 2014); as being "increasingly good and gaining more and more experience" in the PIL arena, and as having expertise extending to "state-to-state disputes, law of the sea, sovereign immunity issues and human rights law" (Chambers 2013); as "quickly establishing a reputation as an 'excellent junior' for a wide array of PIL matters" and as having "supported many of the leading silks in the field on investment protection disputes, international human rights law cases, and issues of sovereign immunity, state succession and the law of the sea" (Chambers and Partners 2012); as having "a growing practice in a wide range of PIL matters, including maritime delimitation, [ICSID] cases and immunity/succession matters" (Chambers and Partners 2011); as handling "all aspects of PIL"; as being "held in high regard by his peers" (Chambers and Partners UK 2010), and as "extremely intelligent, astute and very practical," (Chambers and Partners UK 2009).

In addition to his work in public international law, Simon also has experience in domestic practice, advising and providing advocacy in general chancery and commercial law (including in particular arbitration matters). He has appeared in the County Courts, as well as in the High Court (Chancery Division, Queen's Bench Division, Commercial Court and Mercantile Court).

He publishes regularly in the field of public international law, and is a contributor to the 'International Relations Law' title of Halsbury's Laws of England (5th ed., 2010'; vol. 61) (6th ed., forthcoming 2017).He has also provided commentary for television on questions of international law, and has been invited to speak at academic conferences in the UK, Romania and Ukraine.

Prior to coming to the Bar, Simon was a Research Associate and subsequently Fellow at the Lauterpacht Centre for International Law of the University of Cambridge, with which he still retains links. He acted as assistant to Professor James Crawford, Special Rapporteur on State Responsibility, in the summer of 2001 during the International Law Commission's final consideration and adoption of the Articles on Responsibility of States for Internationally Wrongful Acts and accompanying commentaries. Previously, he also acted for a time as an external legal adviser to the Permanent Mission of Austria to the United Nations, New York.

Simon was a Visiting Fellow at the British Institute of International and Comparative Law from February to August 2007, during which time he undertook a research project, partially funded by the Foreign and Commonwealth Office, investigating reliance on the International Law Commission's Articles on State Responsibility by international and domestic courts and tribunals.

In May 2009, at a ceremony in Bucharest hosted by the President of Romania, Simon was made Cavaler (Knight) of the Ordinul Naţional "Serviciul Credincios" of Romania (National Order "Faithful Service") in recognition of his work on behalf of Romania in the Case Concerning Maritime Delimitation in the Black Sea (Romania v. Ukraine) before the International Court of Justice.

He is a member of the European Society of International Law (ESIL) and the British Branch of the International Law Association (ILA), and a Member of the ILA's Committee on Baselines under the International Law of the Sea. He is also a member of the Editorial Board of the Journal of International Dispute Settlement. and a member of the drafting group for the SHARES 'Commentaries on the Law of International Responsibility' (Amsterdam Centre for International Law (UvA).


Recent Work and Notable cases



Forthcoming Publications