León Castellanos Jankiewicz

León Castellanos-Jankiewicz is a senior researcher in international law at the University of Amsterdam Faculty of Law and the Asser Institute for International and European Law in The Hague. He regularly advises governments on matters of international law and has extensive experience in projects involving interdisciplinary research, multistakeholder engagement, and advocacy.

His research covers three broad fields. First, he is interested in arms trade and weapons transfer policy, in particular human rights safeguards, export controls, corporate accountability and due diligence. Second, he looks at the governance of global public goods through private law, including strategic litigation and supply chain resilience. Finally, he researches legal history, focusing on the intersection of ideas between public and private international law.

Castellanos-Jankiewicz is the principal investigator of the RELY Project: Rearming Europe with Legal Accountability, which develops actionable legal safeguards and human rights risk mitigation strategies at the European Union level to prevent corporate and state misconduct related to wrongful weapons transfers as the bloc ramps up its defence capabilities.

Previously, he was a Max Weber Postdoctoral Fellow at the European University Institute (2017-18) and has held visiting positions at the University of Giessen (2023; 2025), the University of Cambridge (2017) and Harvard Law School (2015-16). He is the inaugural recipient of the David D. Caron Prize of the American Society of International Law (2019) and holds a PhD in International Law from the Geneva Graduate Institute.