Prof. dr. Stef van Weeghel
Prof. dr. Stef van Weeghel is Professor of International Tax Law at the University of Amsterdam. His research focus is on interpretation of tax treaties, tax treaty abuse, and on the interaction between tax law and international investment agreements. Stef has extensive experience in tax policy, counselling and tax controversy. He acts as counsel and as expert witness in tax litigation and in arbitration proceedings. Stef was Global Tax Policy Leader at PwC. Prior to joining PwC, he was partner at law firms Linklaters and Stibbe where his roles included membership of the Executive Committee, head of tax practice and resident partner in the New York office. He was chair of the Permanent Scientific Committee of the International Fiscal Association (IFA) and chair of the Board of Trustees of the International Bureau of Fiscal Documentation (IBFD). He was consistently ranked in band 1 in Chambers and similar guides while practicing at law firms.
- Key Areas of Focus:
- International tax law
Tax treaties
Investment treaties and arbitration - Leadership
- Editorial Board, Intertax
Member of the BRITACʘM Advisory Board
Former Chair, IBFD Board of Trustees
Former Global Tax Policy Leader at PwC
Former Chair of the Permanent Scientific Committee of the International Fiscal Association (IFA) - Recognition
- Band 1, Chambers & Partners
The Best of the Best, Euromoney
Błażej Kuźniacki, Ph.D., Hab.
Błażej is a peripatetic scholar in tax law and international investment law with qualification as an attorney-at-law (Warsaw Bar Association) and a rich practical experience from a private sector (e.g. PwC, CMS) and the public sector (ministry of finance). Holding academic positions of Professor of Law at the Lazarski University (since 2023) and External Senior Research Affiliate at the Singapore Management University – Centre for Digital Law (since 2023), he is the award-winning author of more than 150 scientific publications with national and global coverage, including four books. For the book “Beneficial Ownership in International Taxation” (2022), Błażej was awarded with the International Fiscal Association (IFA) Mitchell B. Carroll Prize in 2023.
In the academic year 2026-2027, Błażej holds a position of Michigan International & Comparative Law Research Scholar at the Center for International and Comparative Law – University of Michigan Law School (USA) as a laureate of the Fulbright Senior Award.
Many authoritative sources, e.g. apex courts in Brazil, Poland and Switzerland, the OECD, the WBG, the CIAT and other scholars across the globe cite Błażej’s work to support their reasoning in jurisprudential, tax policy and academic pieces. He speaks frequently on international tax law, investment tax related disputes, next to his practice in these fields, including expert witness’s opinions and acting as special counsel. He also conducts research and lectures on artificial intelligence and cybersecurity in the tax domain.
- Key Areas of Focus — Practice:
- Tax treaties and prevention of abuse of tax law
Tax controversy and dispute resolution
Intersection of taxation with international investment law, international trade law and customary international law
Global tax policy - Key Areas of Focus — Research:
- Interpretation of tax treaties, EU treaties, and international investment agreements
Beneficial ownership and anti-abuse rules (GAAR, PPT, general principle of prohibition of abuse of rights)
Taxation and international investment law
AI in tax law - Recognition
- Fulbright Senior Award 2026-2027
IFA Mitchell B. Carroll Prize 2023
IFA President YIN Scientific Award 2016
Norway Branch IFA YIN Scientific Award 2016
Rector’s Award for Outstanding Academic Achievements in the Field of Tax Law and Popularization of the Nicolaus Copernicus University’s Name 2010 - Cited by
- Supreme Administrative Court of Poland
Supreme Court of Switzerland
Administrative Council of Tax Appeals in Brazil
OECD · World Bank
European Parliament’s Commissioned Expert Works
