Zhaohang Sun is a Guest Researcher (Gastwissenschaftler) at the Chair of Public Law and International Law (Prof. Dr. Heike Krieger), Freie Universität Berlin. He is also a PhD candidate in Jurisprudence at Jilin University School of Law (supervisor: Prof. Du Yanlin). His work focuses on legitimacy in international law and foundational legal philosophy, with particular interest to adjudicative authority and the operation of legal institutions.

His doctoral dissertation, A Jurisprudential Reappraisal of the Legitimacy Justifications for Extraterritoriality in International Law, examines the normative bases, conditions, and limits of extraterritorial application. He has participated in several national and provincial research projects in China. His articles have appeared in Chinese peer-reviewed journals including Science, Technology and Law, International Business Research, and Social Science International.

During his stay at Freie Universität Berlin, he will focus on three connected lines of inquiry:

1. Legitimacy of extraterritoriality — clarifying the theoretical foundations of extraterritorial application in public law and economic regulation, and mapping its principled limits.
2. Systemic issues of the WTO — analyzing sources of authority, the consent basis of members, and the sustainability of alternative arrangements to the Appellate Body.
3. Due diligence in international law — assessing the normative function of due diligence obligations for states and other relevant actors, its sources of legitimacy, and its potential to crystallize as customary international law.

Methodologically, his research combines jurisprudential analysis with institutional comparison, aiming at clear justification and practical operability. He regularly engages with debates on international adjudication, rule-making, and the relationship between rules, judgment, and social acceptance.

Publications

• 杜宴林,孙兆航.涉外次级制裁的合法性论证“技艺”——以美国为重心的考察[J].世界社会科学,2025,(02):216-241+248. "The Art of Legitimacy Argumentation in Extraterritorial Secondary Sanctions: A U.S.-Centered Analysis" (Social Science International, 2025(2))

• 杨立民,孙兆航.论CPTPP框架下金融服务相互承认制度及中国应对[J].国际商务研究,2024,45(06):82-96.DOI:10.13680/j.cnki.ibr.20241105.002. "Mutual Recognition System of Financial Services under CPTPP and China's Response" (International Business Research, 2024(6))

• 孙兆航,杜宴林.数字平台“守门人”引入问题研究[J].科技与法律(中英文),2024,(02):98-107.DOI:10.19685/j.cnki.cn11-2922/n.2024.02.010. "Gatekeepers in Digital Platforms: Regulatory Implications" (Science Technology and Law, 2024(2), Chinese-English version )

• 孙兆航.论监管一致性规则与美国“非正式帝国”的关联关系[J].北大国际法与比较法评论,2024,18(00):134-151. "Regulatory Coherence and US ‘Informal Empire’ in International Law" (PKU International and Comparative Law Review, 2024)