Twenty Essex

Boundary delimitation; Human rights; Immunities; International arbitration; International criminal law; International dispute settlement in the ICJ; International environmental law; Laws of war; Private international law; Public international law

Monica is a specialist in public international law and international arbitration. She is featured in The Lawyer Hot 100 2020 as amongst “the most daring, innovative and creative lawyers” in the United Kingdom and has won ‘Environment Junior of the Year’ at the Chambers and Partners UK Bar Awards 2023. Monica was ‘Barrister of the Year’ Finalist in The Lawyer’s Awards 2020 and is recognised as a leading practitioner in public international law in the main legal directories which describe her as a ‘highly respected international lawyer’ possessing ‘amazing brainpower’ and delivering ‘excellent oral submissions… impressive on paper and on her feet’; as a barrister with a ‘sharp intellect, dedication and excellent knowledge of the law and experience, willing and able to think outside the box’; ‘incredibly hard working with a fine eye for detail’ and as ‘a great junior who will take Silk before too long.’

Monica is a generalist public international advocate. She was awarded the prestigious Diploma of the Hague Academy of International Law early in her career for demonstrating exceptional command of the entire canon of public international law areas. Her practice in public international law is substantial and covers the full spectrum in the field, including statehood, treaty interpretation, state responsibility, the law of immunities, investment law, law of the sea, boundary delimitation, transboundary environmental damage, environmental law, UN law, the law of international organisations, diplomatic protection, consular law, self-determination, human rights, use of force, international refugee law, humanitarian law, international criminal law and international dispute settlement. She has made seminal contributions in various specialist areas of public international law.

Monica’s practice also covers private international law (acting increasingly, in group litigation), international arbitration and public law. In addition to counsel work, Monica also accepts appointments as arbitrator. Prior to the Bar Monica trained in a civil law system.  Her dual training in the common law and civil law systems (with fluency in legal technical Spanish) is making her a popular choice as counsel/arbitrator in international arbitration cases.  She is currently sitting as co-arbitrator in an USD $70 million+ LCIA arbitration and recently sat as Chair in a €1.2 billion+ claim investment arbitration with a seat in The Hague. Monica has been a guest lecturer at the LCIL Executive Course on Investment Law and Arbitration, University of Cambridge. She is in the UK-Korea FTA  and UK-Japan CEPA dispute resolution lists of arbitrators (proposed by the UK) and was appointed by the government of Malaysia to the Advisory Council of the Asian International Arbitration Centre (AIAC).

Regularly instructed in complex and high-profile cases, Monica acts as counsel for Sovereign states and private parties in cases before English courts, international courts and arbitral tribunals under a variety of rules and applicable laws. She has acted and advised in cases before the Court of Appeal, the High Court, the International Court of Justice (ICJ), Permanent Court of Arbitration (PCA), International Tribunal for the Law of the Sea (ITLOS), OECD procedures, UN human rights treaty-based and Charter-based bodies, regional human rights Courts, East African Court of Justice, ICSID, SCC, LCIA and SIAC tribunals, International Criminal Tribunal for ex-Yugoslavia (ICTY), UN Special Procedures and diplomatic fora. She is admitted before the International Criminal Court (ICC). Increasingly, she is instructed to appear also in foreign courts. She advises in English, Spanish and French.

Monica is considered to be one of the preeminent experts in climate change and environmental litigation worldwide. She provided seminal advice to Sovereign States on the feasibility of an Advisory Opinion on climate change before the ICJ and ITLOS, and her expertise in this area of law is acknowledged in her appointment to the IUCN World Commission on Environmental Law (Oceans and Climate Change Specialist Groups). Notably, she was a speaker addressing the topic of the “World Court and Climate Change” at COP26 in Glasgow and is currently acting for a Sovereign State in Obligations of States in Respect of Climate Change in the ICJ, for a party in the Advisory proceedings on Climate Change and Human Rights in the Inter-American Court of Human Rights, and was instructed in the Request for an Advisory Opinion on Climate Change and International Law before ITLOS (for WWF). Monica also acted in the first climate change contentious case before the UN Human Rights Committee, the Torres Strait Islanders case, securing a landmark decision protecting the rights of peoples in low-lying islands, and in the ground-breaking Los Cedros case, the first ‘Rights of Nature’ case in the world, before the Constitutional Court of Ecuador. In recent years she has been active in cases raising sea-level rise issues, sinking islands, environmental degradation, oil spills, transboundary harm, climate change as a human right issue, environmental harm of waterways, protection of rivers, biodiversity, phasing-out coal mining cases and the enforcement of the Paris Agreement before a variety of international organs. She also advised a State Party representative of a Least Developed Country in the drafting of the Rules of Procedure of Compliance with the Paris Agreement and acted as adviser for a party at COP28 on proposals of a text for a fossil fuels resolution, contributing to the historic adoption of a COP28 Resolution on fossil fuels containing unambiguous language. Monica’s work has been featured in the documentary series Earthrise, ‘Planetary Justice’ by Al Jazeera, broadcasted in 2022 and 2023.

Monica’s current international practice also includes advising in matters relating to Statehood and Self-Determination before UN political organs (GA, UN Security Council, and the UN Special Committee on Decolonization). In litigation in English Courts, Monica has developed expertise in Group Litigation and recently appeared in a high-profile torts group claim in the energy sector raising conflict of law issues in the High Court. Her recent work also includes acting in a deprivation of nationality case and in technology-related cases involving bulk surveillance and the right of privacy (Gençay Bastimar v Turkey), and successfully defending a claim in the first case in which the OECD Guidelines have been applied to a digital dispute involving cryptocurrency.

Monica is an expert in the substance and procedure (including service of process) of diplomatic immunity, state immunity, and the immunity of State officials and special missions. She is also an expert in consular law, in all aspects of the Vienna Convention on Consular Relations. From 2018 to 2019 she served as Assistant Legal Adviser to the Foreign and Commonwealth Office where she routinely advised in those areas, including in the implementation of the Supreme Court judgment in Benkharbouche (in which the UKSC held the incompatibility of sections of the State Immunity Act with Article 6 of the European Convention on Human Rights). During her time at the FCO, Monica advised in a broad number of cases raising sensitive extra-territorial issues, and led  the litigation on behalf of the FCO, in Verica Tomanovic and others v FCO, in the High Court (alleged vicarious liability for human rights violations of the contributing state to EULEX) and Foreign Commonwealth Office v Bamieh [2019] EWCA Civ 803 (relating to the extra-territorial application of the Employment Rights Act 1996) in the Court of Appeal.

Recent notable work includes acting for a Sovereign in an employment case rising issues of State immunity decided in The Royal Embassy of Saudi Arabia (Cultural Bureau) & Ms A Alhayali); acting in the judicial review of Harry Dunn’s parents against the Secretary of State for Foreign and Commonwealth Affairs (raising nuanced aspects of diplomatic immunity), advising a UN Specialised Agency on the immunity of international organisations and arbitration in complex contracts, advising in the high-profile US$1 billion gold dispute relating to the Central Bank of Venezuela (on recognition of governments and executive certification before commercial courts), and advising a State sitting on the board of the World Bank on immunity matters. Her expertise in the area of immunities is reflected in her forthcoming book Foreign State Immunity and Enforcement of Arbitral Awards in English Courts to be published by Oxford University Press.

Monica’s career at the Bar is built on significant experience working for international courts and tribunals which include the International Court of Justice where she advised in the seminal case on Genocide (Bosnia v Ex-Yugoslavia), and the ICTY (Chamber Trial I) where she advised on international humanitarian law and the law of command responsibility. Her experience working with international law institutions includes assisting members of the International Law Commission (ILC) drafting comments to the ILC Draft Articles on State Responsibility, acting as Amicus (with the ILC Special Rapporteur on Diplomatic Protection); drafting responses relating to UN Special Procedures; acting as expert to the Final Report of the Independent Expert on the right to reparation for victims of gross violations of human rights and humanitarian law; assisting in the drafting of UN General Assembly Resolutions (in an advisory capacity); and serving as legal adviser to a State Delegation to the Diplomatic Conference that negotiated the Rome Statute and established the ICC.

Monica’s litigation work in public international law has been cited in Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda)  in the ICJ, in the Reparations Order in The Prosecutor v Bosco Ntaganda and in the Katanga case by the ICC, as well as in proceedings before UN organs. Her scholarship has been referred to in proceedings before the ICJ in in the case of Avena and Other Mexican Nationals (Mexico v United States of America), by the African Court on Human and People’s Rights, by the UN Secretary General on a Guidance Notes on Reparations under International Law, and by Lord Carnwath of the UK Supreme Court.

Monica has published extensively in the area of public international law (with recent contributions to the Max Planck Encyclopedia of International Procedural Law, a Chapter in a seminal book on Deep Sea Mining together with Judge Kamga of ITLOS, several publications on climate change and international courts, and a Chapter on arbitration-related applications before the European Court of Human Rights in International Arbitration and EU Law). She is the editor of International Law for the 21st Century: Essays in Honour of A.A. Cançado Trindade (Asser Press, Springer, forthcoming). Her latest scholarship in investment law and arbitration was designated compulsory reading at the Hague Academy Private International Law course in The Hague. She has lectured and been a speaker worldwide including as guest lecturer at Oxford University; Kurt Bosch-University of Fribourg, Switzerland; Guangxi Normal University (Faculty of Law), China; the United Nations (Geneva); Council of Europe; Lancaster House (FCO); Trinity College, Dublin (Distinguished Speakers Series); the British Institute of Comparative and International Law; Universidad de los Andes Law Faculty (Colombia); Universidad Autónoma de Mexico; Universidad de Chile (Faculty of law), the National & Kapodistrian University of Athens (Faculty of Law); Jindal Global Law School (India); Scuola Superiore Sant’Anna (Pisa); FGV Rio de Janeiro Law School; NUS Centre for International Law – CIL eAcademy (Singapore),and Georgetown University Law Centre. She has held academic positions at the Lauterpacht Centre for International Law (University of Cambridge) (Visiting Scholar and Partner Fellow), and at the London School of Economics (as Teaching Assistant to H.E. Christopher Greenwood, former ICJ Judge). In 2021, she was elected Visiting Fellow at Jesus College, University of Cambridge.

Monica has taken part in expert missions to Kenya (2020), Myanmar (2016), Guatemala (2015), and has trained advocates in South Africa on international law (2017), Colombian lawyers on judicial processes in the context of transitional justice (2017), and members of the Bar in Honduras on international arbitration (2016).

She has been appointed to the Equality and Human Rights Commission’s Panel of Preferred Counsel (B Panel) who are generally instructed where “substantial knowledge and experience is required” in cases of great public importance concerning the Equality Act 2010 and human rights breaches in litigation before domestic and European Courts. Monica was benched at the Middle Temple in 2021.

Spanish (fluent); French (fluent); German (proficient)