I represent sovereign States and State-owned entities in high-stake international disputes.
Hannah Sweeney is a member of the International Litigation & Arbitration Department. Her practice centers on representing and advising sovereign States on matters involving public international law and international arbitration.
London School of Economics and Political Science, M.Sc., with distinction, 2020
University of Pennsylvania, B.A., summa cum laude, 2019
Bar and Court Admissions
BAR ADMISSIONS
New York
Languages
German
Experience
INTERNATIONAL INVESTMENT ARBITRATION
Warburg Pincus and others v. Republic of Poland. Counsel to Poland in an ICSID arbitration under the Poland-United States bilateral investment treaty relating to measures in the pharmaceuticals sector.
Adria Group B.V. and Adria Group Holding B.V. v. Republic of Croatia. Counsel to Croatia in an ICSID arbitration under the Croatia-Netherlands BIT arising from alleged investments in a retail enterprise in Croatia.
INTERNATIONAL LITIGATION IN U.S. COURTS
Cisco Systems Inc. et al. v. Doe I, et al. Counsel to amici former U.S. Ambassadors-at-Large for War Crimes Issues/Global Criminal Justice and Prosecutors of International Crimes in amicus brief before U.S. Supreme Court on scope of aiding and abetting liability under the Alien Tort Statute and Torture Victims Protection Act.
Gabor Rona and Lisa Davis v. Donald J. Trump et al. Counsel for two professors of international criminal law in an action in the U.S. District Court for the Southern District of New York successfully challenging the constitutionality of a Trump Administration Executive Order concerning the International Criminal Court.
Successfully represented the Prime Minister of Antigua & Barbuda in opposing a Section 1782 discovery application in the U.S. District Court for the Southern District of New York and in the Second Circuit.
Advising States regarding arbitration award enforcement/annulment strategies in U.S. courts.
INTERNATIONAL COURT OF JUSTICE
The Gambia v. Myanmar. Representing The Gambia before the ICJ in Application of the Convention on the Prevention and Punishment of the Crime of Genocide (The Gambia v. Myanmar).
PRO BONO AND OTHER EXPERIENCE
Assisted the International Bar Association and the Human Rights Foundation in a public enquiry concerning the human rights situation in Xinjiang and the treatment of the Uyghur population.
Counsel to refugees seeking humanitarian parole relief and asylum in the United States.
Assisted an international women’s rights organization with a submission to the United Nations Human Rights Council’s Universal Periodic Review of Afghanistan.
Participated in a Study Group led by the American Branch of International Law Association with the purpose of examining and proposing changes to States on various provisions of the draft Crimes Against Humanity treaty.
Served as an aide to the American Society of International Law’s Signature Topic on Gender Justice.
PRIOR PROFESSIONAL EXPERIENCE
Graduate Researcher at the Harvard Program for International Law and Armed Conflict.
Teaching Fellow at Harvard Law School for Public International Law and Laws of Armed Conflict.
Legal Intern with the Kosovo Specialist Chambers in The Hague.
Intern with the U.S. Mission to the U.N. Human Rights Council.
Other Publications
“Gender Equality and State Responsibility: Enforcing CEDAW through the ICJ,” Harvard Human Rights Journal (forthcoming Spring 2025)
Co-authored with Dustin Lewis, “Exercising Cognitive Agency: A Legal Framework Concerning Natural and Artificial Intelligence in Armed Conflict,” Harvard Law School Program on International Law and Armed Conflict (January 2025)
“The International Court of Justice: A Year in Review,” Lawfare (November 6, 2023)
Co-authored with Alexis Jori Shanes and Olivia B. Hoff, “An Assessment of the Ljubljana-The Hague Convention on Mutual Legal Assistance,” Lawfare (September 1, 2023)
Co-authored with Alexis Jori Shanes and Sasa Jovanovic, “The Taamneh and Gonzalez Rulings, Explained,” Lawfare (May 19, 2023)
Co-authored with Dominic Solari, “Human Security and Changing Threats: NATO’s Policies for 2022 and Beyond,” Lawfare (December 5, 2022)
Honors & Involvement
HONORS
John Gallup Laylin Writing Prize for best paper in the field of public international law (2024)
Philip C. Jessup International Moot Court Competition, World Champion (2022), Richard R. Baxter Award for Best Applicant Memorial (2023)
Salzburg Culter Global Fellow for International Law (2023)
Chayes International Public Service Fellowship (2022)
Cravath International Fellowship (2022)
Questbridge Match Scholar (2015)
INVOLVEMENT
American Society of International Law
European Society of International Law
American Branch of the International Law Association
Philip C. Jessup International Moot Court Competition, Judge (2024)
Speaking Engagements
"Non-State Actors & International Climate Adjudication," Pre-Conference Workshop of the Interest Group on International Environmental Law (September 2025)
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