Counting both sovereign states and blue-chip corporations among its impressive roster of clients, A&O Shearman’s public international law team regularly handles treaty accession work, sanctions issues, and issues regarding climate change and the Law of the Sea. Contentious investment treaty work, particularly those under the Energy Charter Treaty, constitutes a key pillar of work for the team; David Herlihy, who splits his time between London and Ireland, is a key contact here. Mark Levy KC heads the team and is regularly instructed on investor-State cases, while Guled Yusuf has a focus on disputes in the energy, mining, and infrastructure sectors, as well as ITLOS, WTO, and ICJ proceedings. Katrina Limond, a public international law specialist, is another key individual.

The ‘utterly brilliant and indispensable’ public international law team at Clifford Chance LLP has notable strength advising on treaty negotiation, climate change, and sovereign immunity matters. The ‘extremely knowledgeable’ Jessica Gladstone heads up the practice and stands out for her extensive experience advising on both contentious and non-contentious public international law matters, including human rights, international trade, and investor treaty issues. Rae Lindsay’s practice focuses on business and human rights issues, including international humanitarian and criminal law work. Other key individuals include Anna Kirkpatrick and Carla Lewis, who assist on human rights and governance matters and international arbitration, respectively. Audley Sheppard KC left the firm in June 2025.

Debevoise & Plimpton LLP fields a ‘thoughtful, measured, and always prepared’ team that leverages the firm’s global capabilities to provide a comprehensive public international law offering. Acting for sovereign states, treaty bodies, and multinational corporations, the team regularly handles ECT treaty claims, ICSID arbitrations, and ICJ advisory proceedings. The ‘invaluable’ Lord (Peter) Goldsmith KC and Jeffrey Sullivan KC jointly co-head the practice; Goldsmith has extensive experience before both domestic and international courts and tribunals, while Sullivan focuses his practice on ECT issues and general international arbitration. ‘Fantastic legal strategist’ Conway Blake has a broad practice that covers the Law of the Sea, sovereign and diplomatic immunity issues, and environmental, human rights, and investment treaty matters, while Samantha Rowe is the name to note for international disputes regarding treaty law, state succession, and maritime boundary issues. Monika Hlavkova rounds out the division and assists on investment and commercial arbitrations. Aimee-Jane Lee left the firm in 2025.

Dedicated public international law boutique firm Fietta LLP stands out for its specialised and market-leading offering, handling the full spectrum of public international law work for sovereign state clients as well as investors. Investment treaty disputes, inter-state mediation proceedings, and ICJ proceedings all form core pillars of work for the practice. The ‘outstanding and excellent’ Stephen Fietta KC, founding partner, acts for state clients on the full range of PIL work, handling investment arbitration cases, Law of the Sea disputes, international humanitarian law and the law of armed conflict. This is supplemented by expertise in territorial, sovereignty, and natural resources disputes before an array of international courts of tribunals, including the ICJ, ITLOS, ECtHR, and ICSID and UNCITRAL. Laura Rees-Evans advises on inter-state proceedings before the ICJ, PCA, and ECtHR, while the ‘fantastic’ Oonagh Sands has an active caseload before the ICJ; Sands also handles a high volume of investment treaty cases. Fietta, Rees-Evans, and Sands jointly lead the team; the trio is ably assisted by Miglena Angelova.

Freshfields’ public international law team has extensive experience handling inter-state disputes, high-profile investor-state arbitrations, and advisory international law work for a range of clients, including sovereign states, international organisations, and global corporations, with notable sector expertise in the energy, natural resources, mining, and telecoms industries. Will Thomas KC leads the team and attracts praise for his ‘brilliant cross-examination skills and excellent strategic judgment’; Thomas has notable expertise handling state-to-state disputes before the ICJ and ECHR as well as ad hoc tribunals. Sylvia Noury KC has a focus on investment treaty arbitrations in Africa, India, and Latin America. Other key members of the team include Joshua Kelly, who focuses his practice on advisory matters, as well as Camille Strosser, who ‘combines raw intelligence with unusually good judgement.’

Clients in the natural resources, energy, and mining sectors regularly seek the assistance of Herbert Smith Freehills Kramer LLP’s public international law team, which stands out for its strength in advising both investors and states in investor-state disputes, as well as advising on investment treaty drafting. Andrew Cannon has a broad PIL practice with an emphasis on bilateral and multilateral treaty work, both contentious and non-contentious, and attracts praise for his ‘incisive advocacy’. Cannon leads the firm’s global PIL team alongside co-head Christian Leathley, a seasoned international arbitrator with notable industry expertise in the energy, mining, and telecoms sectors. Hannah Ambrose takes point on investment treaty claims and investment structuring matters, in addition to supporting on state immunity and boundary delimitation issues. Also in the core team are Louise Barber and Joel Halliday, who ably assist on international arbitration matters.

Specialist public international law boutique firm Volterra Fietta counts several sovereign states and state-backed entities amongst its impressive roster of clients, handling the full range of PIL work, including advisory opinion proceedings before the ICJ and other international courts, ICSID treaty arbitrations, as well as international law proceedings before domestic courts. Treaty negotiation, sanctions, and business and human rights issues constitute further pillars of work for the team. Robert Volterra has a strong track record advising sovereign states on climate change, state immunity, and land and maritime boundary issues before the ICJ. Peter Flint takes point on international arbitration matters, acting for governments and global corporations; Gunjan Sharma is a key contact for international environmental law and maritime delimitation work; while Ahmed Abdel Hakam has a focus on international disputes in the energy and natural resources sectors. The four jointly lead the ‘unique’ team and are ably assisted by Angela Ha and Magdalena Kowalczuk Asher.

Arnold & Porter’s public international law offering stands out for its strength in advising sovereign states on a range of contentious mandates, particularly investment treaty arbitrations, with a notable focus on arbitrations in Latin America. ICSID arbitration is another significant pillar of work for the group. Practice co-heads Patricio Grané Labat, described as ‘fiercely committed with a razor-sharp intellect’, and David Reed take point on investor-state arbitration and international investment treaty arbitrations, respectively. Also in the core team is Álvaro Nistal, who was elevated to the partnership in January 2025 and is praised by clients for his ‘commercial acumen and a tenacious work ethic’; Nistal acts for sovereign states and international organisations on a broad range of contentious PIL matters.

Latham & Watkins stands out for its strength in investment treaty work, handling a high volume of ICSID work as well as ECT matters. Leveraging its international capabilities, the team also advises on issues of state immunity and human rights. Charles Claypoole, hailed by clients as ‘a highly sophisticated lawyer with terrific communication skills’, heads up the team; Claypoole’s practice focuses on international trade law, state immunity issues, and investment treaty arbitration. Sophie Lamb KC is another name on the investment treaty arbitration front, with a strong track record acting for both investors and state clients. Robert Price handles international trade law, export control issues, and sanctions work; Thomas Lane is another key contact here.

Attracting client praise for its ‘commercial awareness, responsiveness, and unwavering commitment to client objectives’, Quinn Emanuel Urquhart & Sullivan, LLP has notable industry strength in the energy and infrastructure sectors, handling investment treaty arbitrations for both state and investor-side clients. Arbitration specialist trio Stephen Jagusch, the ‘brilliant’ Anthony Sinclair, and Epaminontas Triantafilou jointly lead the team. Jagusch specialises in investor-state arbitration in the energy and construction sectors; Sinclair handles energy and mining sector work; while Triantafilou has previous experience from the PCA.

Constantine Partasides KC and Reza Mohtashami KC jointly lead the public international law offering at international dispute specialist firm Three Crowns LLP, which is praised for its ‘great depth of expertise’. Partasides has a strong track record advising on high-value international arbitrations, while Mohtashami takes point on investor-state disputes, particularly in the Middle East. Gaëtan Verhoosel KC handles investment treaty disputes, with particular expertise in the power, oil and gas, and renewables industries, and Manish Aggarwal, who is dual-qualified in India and England, is another notable individual on the investor-state arbitration front, as is Leilah Bruton. The team is ably assisted by Farouk El-Hosseny and Ridhi Kabra.

Withers LLP counts sovereign states, international organisations, and multinational corporations among its impressive client roster. Work regarding the Law of the Sea, both contentious and advisory, is an area of notable strength for the team, as are BIT disputes and work regarding sanctions. ‘Precise advocate and excellent negotiator’ Hussein Haeri KC leads the practice, bringing a strong track record in advising sovereign states on contentious matters, including human rights, boundary disputes, and state immunity issues to the department. Robert Kovacs focuses his practice on business and human rights matters as well as international arbitration. Ruzin Dagli and Camilla Gambarini are recommended for matters concerning international investment, the Law of the Sea, and human rights issues.

ICSID arbitrations and investor-state arbitrations for sovereign states constitute a core area of work for the international disputes team at Baker Botts (UK) LLP. Practice head Johannes Koepp has notable expertise advising on international arbitrations in the telecoms, defence, and financial services industries, while Alejandro Escobar acts for governments, corporations, and state entities on matters regarding investment contracts, ICSID arbitrations, and treaty issues. Dorine Farah is another key contact for investment treaty arbitration, as is David Turner. Also in the core team, Ernesto Féliz De Jesús has a focus on Latin American disputes.

Carter-Ruck advises on a high volume of ICSID arbitrations, acting for individual businesspeople, multinational companies, and sovereign states. The group also has a notable emphasis on sanctions issues; Charles Enderby Smith is the name to note here. Cameron Doley heads up the team and has ‘a wealth of experience in international disputes’, advising governments, heads of state, and companies before various international courts, including the ECJ, ECHR, and the International Criminal Court. Guy Martin left the firm in 2025.

With notable expertise in international maritime law and the Law of the Sea, Cooley (UK) LLP acts for sovereign states and corporations on issues of maritime boundary delimitation, freedom of navigation, and continental shelf matters. James Maton leads the team and has a focus on treaty disputes and investor-state arbitration; Juan Nascimbene is another name here. Consultant John Brown takes point on Law of the Sea matters, with notable expertise in maritime boundary delimitation and freedom of navigation issues.

Charles Buderi and Luciana Ricart jointly lead the ‘absolutely exceptional’ public international law team at Curtis, Mallet-Prevost, Colt & Mosle LLP, whose expertise spans maritime delimitation, state immunity, and international human rights law issues, as well as providing representation before international courts. Buderi and Ricart, described by clients as ‘a powerhouse’, both advise on PIL issues as well as investment arbitrations, primarily acting for sovereign states and state entities. Lise Johnson is another key member of the team, her practice spans human rights and business, climate change, and international investment law.

Jonathan Leach heads up the public international law offering at Eversheds Sutherland (International) LLP, which stands out for its strength in treaty arbitration. Leach takes point on investor-state arbitrations, acting for both states and investors, and is described by clients as ‘outstanding’. The ‘highly committed’ Katia Finkel has a strong track record handling investment treaty arbitration, particularly in the infrastructure sector, while Wilson Antoon has a focus on investor-state arbitrations in the mining and energy sectors.

Michelle Bradfield heads the ‘unusually well-qualified’ public international law team at Jones Day, which advises on treaty investment claims, treaty succession matters, and human rights issues. The ‘simply excellent’ Bradfield acts for states and international organisations on boundary disputes, maritime delimitation, and treaty interpretation matters. The group also handles advisory work regarding climate change and international environmental law for clients in the energy industry. Lee Coffey is a key contact for international arbitration; Elizabeth Robertson is a name to note for EU law, ESG matters, and sanctions; while Alex Chalk KC joined from 6KBW College Hill in January 2025, strengthening the firm’s international commercial arbitration offering.

Working in close collaboration with the firm’s Geneva and New York offices, the public international team at King & Spalding LLP acts for a diverse range of clients, including sovereign states, multinational corporations, and individuals. Thomas K. Sprange KC heads up the team, which handles inter-state territorial disputes, international humanitarian and human rights law, Law of the Sea matters, and investment treaty arbitration. Sprange advises on sovereign immunity, arbitration claims, and BIT disputes; Sajid Ahmed is another key name here. Also in the core team, the ‘exceptional’ Peter Hood takes point on inter-state disputes regarding issues of human rights violations, the Law of the Sea, and climate change, while Max Hill KC is described by clients as an ‘elegant advocate’.

The public international law team at Linklaters LLP sits within the firm’s larger litigation, arbitration, and investigations practice. Under the joint leadership of Matthew Weiniger KC and Charlotte Morgan, the team works closely with the firm’s international network of offices to advise on FTA negotiations, sanctions issues, and business and human rights issues, particularly for clients in the energy sector. Weininger chairs the firm’s international arbitration offering, while Morgan is the co-chair of its trade law practice.

Ryan Junck heads up the international arbitration team at Skadden, Arps, Slate, Meagher & Flom (UK) LLP, which stands out for its strong focus on sanctions matters. The team advises private corporations and financial institutions across a broad range of industries on export control matters, trade sanctions, counter-sanctions, and market exits, as well as issues relating to the interactions between sanctions regimes. Junck is the key contact for sanctions matters, working alongside export control specialist Jonathan Benson.

The ‘incredibly responsive and transparent’ team at Squire Patton Boggs has a busy practice advising on investment treaty arbitrations, sovereign immunity issues, and the enforcement of awards. George Von Mehren co-chairs the firm’s global international dispute resolution group, while Max Rockall and Peter Crossley co-head the London IDR offering. The ‘excellent’ Naomi Briercliffe focuses her practice on investor-state arbitration and general PIL issues, advising international organisations and sovereign states on ICJ advisory opinions, the Law of the Sea issues, and space law matters.

With strength in sanctions advisory, international commercial arbitration, and disputes regarding statehood, the right to self-determination, and boundary delimitation, Stephenson Harwood counts both state entities and multinational corporations among its clients. Head of the practice Kamal Shah is a seasoned arbitrator with notable experience handling international arbitrations; Shah also heads the firm’s Africa and India desks. June 2025 saw the firm strengthening its international arbitration offering with the arrival of Stuart Dutson, formerly at Simmons & Simmons. Other key individuals include Charlotte Welsh, Daniel Boon, and Ellen Dixon.

Acting for individuals, sovereign states, and international organisations, Steptoe UK LLP advises on treaty negotiations, investor-state disputes, and ECT claims. Attracting client praise for its ‘excellent command of international investment law’, the group also handles sovereign immunity matters, expertly overseen by practice head Matthew Coleman. Christophe Bondy has extensive experience advising on investment treaty arbitration, while Thomas Innes is another key contact on the investor-state arbitration front; Innes also has experience in ITLOS proceedings.

With strength in investor-state arbitrations, Stewarts Law LLP’s international arbitration group ably handles instructions for both investor and state-side clients. Sherina Petit heads up the team and specialises in international commercial arbitration, with a focus on India-related disputes across a range of sectors. Described by clients as ‘a supreme source of knowledge and strategy’, Alejandro Garcia has experience acting on arbitrations before various international arbitral institutions, including ICSID and the ICC. For oil and gas and tech-related work, Daniel Wilmot is the name to note. Rovine Chandrasekera joined the firm from Stephenson Harwood in September 2025.

WilmerHale handles a broad range of public international law work, including treaty accession issues, issues of territoriality and sovereignty, human rights violations, and investor-state disputes. Gary Born, Franz Schwarz, and Steven Finizio jointly lead the team. Born is a seasoned expert whose practice covers investment law, international dispute resolution, and state-to-state arbitration; Schwarz has a focus on arbitrations in the financial services space as well as issues relating to foreign investments; and Finizio has experience appearing before the ECHR and the AfCHPR. The team also includes the ‘extremely strategic’ Jonathan Lim, triple-qualified in England, Singapore, and New York.

Clyde & Co’s global dispute resolution group acts for sovereign states and international organisations on a range of public international law matters, including expropriation, sanctions, and BIT and ECT disputes. Ben Knowles heads up the team and has a strong track record handling ICC, ICSID, and PCA arbitrations, particularly in the energy, trade, and telecoms industries. Loukas Mistelis advises on both state-to-state and investor-state arbitrations, while Milena Szuniewicz-Wenzel is praised by clients for her ‘encyclopaedic knowledge of the facts of a case.’

CMS’ public international law group acts for clients in both the public and private sector, handling contentious and advisory mandates regarding sovereign immunity, investor-state disputes, and sanctions compliance work. Karen Denny heads up the ‘very experienced’ practice, being ‘very astute’ and focused on sovereign immunity and the enforcement of awards, while Sarah Vasani heads up the firm’s investor-state dispute resolution offering. Zainab Hodgson is another recommended member of the group.

Gibson, Dunn & Crutcher acts for state entities, private corporations, non-governmental organisations, and individuals on a broad range of public international law matters, including ICSID arbitrations, human rights issues, and advisory work on sanctions. Penny Madden KC is an experienced international arbitrator with a focus on telecoms, international trade, and energy disputes, while the ‘highly authoritative’ Robert Spano draws on his experience as the former president of the ECHR to advise on PIL, business law, and human rights issues. Madden and Spano jointly head the team. Ceyda Knoebel is highly recommended by clients for her ‘in-depth understanding and experience of international arbitration’. Former practice co-head Cyrus Benson left the firm in May 2025.

Mayer Brown International LLP leverages the firm’s international network of offices to advise on investor-state and state-to-state international disputes, handling ICSID and UNCITRAL arbitrations as well as arbitrations under the ECT. Raid Abu-Manneh heads up the team and also co-heads the firm’s global international arbitration practice, while Rachael O’Grady is a key name for bilateral investment treaty arbitration matters.

Public international boutique firm Paxus LLP is regularly instructed by multinational corporations in a diverse array of sectors to advise on risk mitigation, human rights and international humanitarian law compliance, and broader business and human rights issues. Founding partner and practice head Suzanne Spears has a strong track record in advising on international human rights and business issues, climate change matters, and US foreign relations law and policy. Spears works alongside Olga Owczarek, who advises corporations on investment treaty arbitration; Sebastián Mejía, who handles investor-state disputes; and Sebastián Abad-Jara, who has a focus on human rights due diligence issues in Latin America.

Michael O’Kane and Anna Bradshaw jointly lead the team at Peters & Peters Solicitors LLP, which stands out for its ‘fantastic’ sanctions and export control expertise. Former Crown Prosecution Service prosecutor O’Kane acts for both individuals and corporations, while Bradshaw is recommended for her cross-border financial crime and sanctions expertise. Alistair Jones, another core member of the department, attracts praise for his ‘in-depth knowledge of the intricacies of UK sanctions law’.

Reed Smith LLP has a focused investor-state arbitration practice, handling UNCITRAL and ICSID arbitrations and enforcement proceedings. Lucy Winnington-Ingram, who was promoted to partner in January 2025, now leads the ‘well-oiled’ practice; Winnington-Ingram is described by clients as ‘immensely technically gifted with excellent knowledge of the law – a natural advocate with superb strategic instincts.’ Also in the core team is fellow new partner Ali Ishaq, described as ‘any client’s dream’.

ICSID arbitrations and arbitrations under the Energy Charter Treaty constitute key pillars of work for the public international law team at Simmons & Simmons. Basil Woodd-Walker, described by clients as ‘talented and utterly trustworthy’, is a key figure in the team. Woodd-Walker is regularly instructed to advise on sovereign immunity issues as well as investor-state arbitrations. Jonathan Schuman ably assists on bilateral investment treaty claims. Former practice head Stuart Dutson left the firm in June 2025.

Tomas Vail is the name to note at boutique firm Vail Dispute Resolution, which has a stand-out emphasis on international arbitration matters. The ‘approachable, proactive, and solutions-oriented’ Vail, a seasoned arbitrator, has a strong track record advising on investor-state disputes in the energy and infrastructure sectors and also handles claims under BITs.