Public international law

Our established team has advised on some of the highest profile and most complex arbitration matters globally and is highly regarded in the field.

We cover the full spectrum of international law work, ranging from advice on State-State disputes before the International Court of Justice (ICJ) and issues of international law that arise before national courts to acting as counsel for parties in Investor-State disputes administered by the International Centre for Settlement of Investment Disputes (ICSID).

Whether you’re looking for advice on international investment law, land and maritime boundary disputes, the law of the sea, sovereign and diplomatic immunity, international sanctions, trade law (including WTO rules), international environmental law, human rights disputes (including before U.N. committees), international humanitarian law, the law of international organisations or enforcement – we can help.

Experience advising both investors and States

We have an established investor-state arbitration practice with numerous investment treaty arbitration cases, representing both international investors and sovereign states.

Our dedicated team works with clients around the world to resolve investor-State disputes under all the major arbitration rules, as well as ad hoc arbitrations across a wide range of sectors including, but not limited to, energy, natural resources, infrastructure, manufacturing, technology, construction and finance.

We have an experienced practice advising Governments on drafting investment treaties and investment legislation, a rare focus in private practice in the field of public international law. We also advise investors looking to ensure their investments are adequately protected from commercial and political risk in the context and framework of international investment law.

International support to suit your needs

Made up of more than 20 lawyers worldwide, our team is spread across London, New York, Milan, Geneva, Singapore, Hong Kong and the British Virgin Islands. Our members are fluent in numerous languages, including French, Spanish, Italian, Russian, Arabic, Chinese, Hindi and Turkish and are qualified in both common and civil law jurisdictions, with extensive experience working in international organisations and emerging markets. We act as strategic advisors, conducting our own oral advocacy in public international law and human rights matters. These key factors contribute to the strength of our practice.

We are able to advise a variety of clients, namely Governments, multinational corporations, international organisations, non-governmental organisations and individuals, in the context of sensitive disputes involving different regions of the world, including in the Middle East, Africa, Asia, CIS countries, Europe, Russia and Latin America.

An outstanding practice

Our team includes leading individuals like the barrister and former Attorney General, The Right Honourable Geoffrey Cox KC MP.

Clients have praised our team’s ‘deep technical knowledge’ and ‘impressive ability to assess and navigate complex legal and factual situations’, whilst also acknowledging our ‘responsiveness and professionalism’ as being ‘of a very high order’ and appreciating our ‘excellent customer focus’.

Members of the public international law team have also been commended for blending ‘strategic thinking with excellent client management skills’ and are known for their ‘practical and creative strategies’.

For further help or information

Get in touch

Награды и признание

2022 Chambers UK: leading firm for public international law

2022 Legal 500 UK, leading firm for public international law

Leading firm for public international law

Leading firm for public international law

Managing political risk

We are in uncertain political times. Whether economic, personal or otherwise, we can help individuals and businesses take practical steps to reduce their exposure.

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Track record


  • Advising a State in a potential State-to-State dispute in relation to international environmental law issues.
  • Advising a State in relation to discrimination issues arising under a human right treaty.
  • Advising an international organisation in relation to EU-Russia sanctions.
  • Advising a State in relation to issues pertaining to freedom of navigation and the law of the sea.
  • Advising a government in the Middle East on its investment treaty program.
  • Advising an NGO in relation to human rights issues to present a shadow letter to the UN Committee on the Rights of the Child.
  • Advising a German investor in an ICSID investment treaty arbitration claim in relation to discrimination measures taken by an African State.
  • Advising an Italian client in a dispute over an investment in the energy sector and ICSID investment treaty arbitration claim against a European state. Our client is seeking damages for breach of fair and equitable treatment, expropriation and other treaty standards.
  • Conducting an extensive project for a Government client advising them on international investment law issues and drafting an innovative model bilateral investment treaty.
  • Advising a Caribbean Government on a range of international investment law issues.
  • Representing a Mauritian energy company as counsel and advocates in an investment treaty arbitration against Pakistan under the UNCITRAL arbitration rules.
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Hussein Haeri combines deep technical knowledge of investment treaty arbitration with clarity of strategic direction and impressive project management skills. He demonstrates excellent customer focus and sound judgement.

Thomas Le Feuvre, Head of International Agreements, Government of Jersey
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Experienced and knowledgeable across a wide range of PIL areas, especially investment-state arbitration, but increasingly on inter-state disputes too.

Legal 500 UK, 2023
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Their work is outstanding and the team’s commitment is always stellar.

Chambers and Partners UK, 2023
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Withers is a very dynamic firm that’s keen to grow.

Chambers and Partners UK, 2023
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Withers LLP’s team is excellent. The team evinced a very strong knowledge base in public international law and was able to dispense astute strategic advice.

Chambers Global, 2022
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Withers LLP’s public international law practice garners great praise from sources, with one highlighting that “the team has been outstanding and the quality of the work has been stellar.”

Chambers Global, 2022

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