International Tax Investment Arbitration Global Policy
Cross-Border Tax Expertise
Precision refined through decades of experience and guided by passion for tax-related matters.
Core Expertise
Where tax meets international law
Three practice areas, one joint vision of tax law and global tax policy in light of geopolitical developments.
Investment Arbitration & Tax Litigation
Expert testimony and strategic counsel where international tax law meets investment-treaty and commercial arbitration.
Expert Advice in International Tax Law
Conflict-free opinions on treaties, directives, beneficial ownership, anti-avoidance rules and cross-border structures.
Strategic Tax Policy Advisory
Policy advice for governments and international organisations, informed by global reform and geopolitical change.
The Founders
Two disciplines. One direction.
We combine scholarly precision with the pragmatism of advisors who have worked at the intersection of international tax law, arbitration and global policy.
Prof. dr. Stef van Weeghel
Professor of International Tax Law · University of Amsterdam
Former Global Tax Policy Leader at PwC; counsel and expert witness in investment-treaty and commercial arbitration.
Błażej Kuźniacki, Ph.D., Hab.
Associate Professor · Author of 150+ publications
IFA Mitchell B. Carroll Prize laureate; expert on beneficial ownership, abuse, GAAR, CFC regimes, tax and AI.
Pivotal Jurisprudence & Insights
A repository of relevant
case law & strategic insight
AI and the future of tax administration
Why explainable AI is becoming central to revenue administrations worldwide.
The improper use of tax treaties, three decades on
Revisiting the doctrine that defined a generation of treaty interpretation.
Beneficial ownership and the limits of the treaty-abuse doctrine
As apex courts converge on the meaning of beneficial ownership, the doctrine of treaty abuse is being redrawn.
Get in touch
Reach us
Connect with the Founders to explore how our hybrid expertise can add clarity to your cross-border tax challenges.
A rare combination,
at the intersection of disciplines
We offer conflict-free advice on international tax law and its intersections with investment and trade law, customary international law and global tax policy.
Two hybrids that set our counsel apart
Our advice flows through a joint vision of tax law and global tax policy in light of geopolitical developments — combining what is usually kept apart.
Academic rigour × frontline practice
Scholarly precision combined with the pragmatism of advisors who have argued at the highest courts and tribunals.
Tax law × international law
International tax law read together with investment-treaty, trade and customary international law.
What we are engaged to do
Investment Arbitration & Tax Litigation
We act as counsel and expert witness where the tax dimension of a dispute is decisive.
- Expert witness reports
- Tax in investor-State & commercial arbitration
- Cross-border tax controversy
Expert Advice in International Tax Law
Conflict-free opinions on treaties, directives and domestic anti-avoidance rules.
- Tax treaties & beneficial ownership
- Anti-avoidance — PPT, GAAR, ATAD
- EU directives & CFC regimes
Strategic Tax Policy Advisory
We help governments and international organisations shape and stress-test tax policy.
- Advice to governments & ministries
- Engagement with OECD, UN, World Bank
- Evaluation of new policy initiatives
Engage specialized counsel
Tell us about your matter. We will let you know — promptly and candidly — whether and how we can help.
Two disciplines.
One direction.
Van Weeghel & Kuźniacki is not a law firm but an expert platform — a barrister-type chambers. Stef and Błażej act as independent experts who engage individually or jointly.
We combine scholarly precision with the pragmatism of advisors who have worked at the very intersection of international tax law, investment-treaty arbitration and global policy. Our independence is our clients’ advantage. Stef van Weeghel & Błażej Kuźniacki
Prof. dr. Stef van Weeghel
Professor of international tax law at the University of Amsterdam since 2000. He acts as counsel and expert witness in investment-treaty and commercial arbitration and before Dutch and foreign courts.
- Education
- LLM in Taxation, NYU
Doctor of Law, University of Amsterdam - Leadership
- Chair, IBFD Board of Trustees
Editorial Board, Intertax - Recognition
- Band 1, Chambers & Partners
The Best of the Best, Euromoney
Błażej Kuźniacki, Ph.D., Hab.
Author of over 150 publications cited by supreme courts in Poland, Switzerland and Brazil. He delivers expert reports on beneficial ownership, abuse, GAAR and CFC regimes, and advises international organisations on tax and AI.
- Recognition
- IFA Mitchell B. Carroll Prize
- Cited by
- Supreme Administrative Court
Swiss Supreme Court · Brazil CARF - Advisory
- OECD · World Bank
CIAT · European Parliament
A foundation in scholarship
Academic Appointments
- Professor of International Tax Law — University of Amsterdam
- Visiting Professor — International Tax Center, Leiden
- Associate Professor — Lazarski University
- Senior Research Affiliate — Singapore Management University
- Fulbright Senior Research Awardee — Michigan
Institutional & Editorial Leadership
- Chair — IBFD Board of Trustees
- Past Chair — Permanent Scientific Committee, IFA
- Editorial Board — Intertax
- Vice-Chair — Belt & Road Initiative Tax Journal
- Member — Practice Council, NYU Law ITP
Awards & Recognition
Representative
Matters
Selected engagements across investment-treaty and commercial arbitration, apex-court tax controversy and advisory work — presented in anonymized form.
Beneficial ownership under a bilateral income-tax treaty
Investor–State arbitration · Expert witness · Asia–Europe
Tax treatment of compensation in an energy-sector dispute
ICSID / PCA proceedings · Expert witness for the Respondent · Central Europe
Permanent establishment and cross-border withholding
Supreme court · Expert witness · South Asia
Beneficial ownership and abuse on a billion-euro dividend flow
Administrative courts · Expert report · European Union
Compatibility of CFC rules with EU law and a bilateral treaty
National courts · Expert report · EU – Switzerland
The tax dimension of a cross-border commercial dispute
UNCITRAL Rules · Expert witness
Interpretation of an advance tax ruling
Special tax counsel · European Union
A living repository of tax-related jurisprudence
Court rulings and arbitral decisions at the intersection of tax, treaty and investment law — open, searchable and continuously updated.
Explore the RepositoryInsights
A repository of relevant case law, scientific publications and strategic insight in international tax and investment law.
AI and the future of tax administration
Why explainable AI is becoming central to revenue administrations worldwide.
July 28, 2026 · 1 min read
Read ArticleThe improper use of tax treaties, three decades on
Revisiting the doctrine that defined a generation of treaty interpretation.
Beneficial ownership and the limits of the treaty-abuse doctrine
As apex courts converge on the meaning of beneficial ownership, the doctrine of treaty abuse is being redrawn.
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Reach us
Tell us about your matter. We engage by referral and direct inquiry — and will let you know promptly and candidly whether and how we can help.
Direct channels
Prof. dr. Stef van Weeghel
Counsel & expert witness — investment arbitration, tax controversy, policy.
Błażej Kuźniacki, Ph.D., Hab.
Expert reports — beneficial ownership, abuse, GAAR, CFC; tax & AI.
General inquiries
Remote and virtual model — no physical office. We respond personally.
The inquiry form is temporarily unavailable. Please use a direct contact channel.
Submitting an inquiry does not create an engagement or any adviser-client relationship. Please do not send confidential information before an engagement is in place. Van Weeghel & Kuźniacki is an expert advisory platform, not a law firm.
Tester
By pof_master · July 27, 2026 · 1 min read
Beneficial ownership is once again at the centre of international tax disputes. Recent rulings reveal both convergence and persistent disagreement over its function.
The expression began as a practical treaty concept. It now operates at the intersection of legal title, economic control and anti-abuse doctrine, making its application especially sensitive in multi-jurisdictional structures.
A doctrine under pressure
Courts increasingly resist mechanical tests. Their reasoning focuses instead on the recipient’s powers, contractual constraints and the commercial context in which income is received and transferred.
Clarity does not come from adding another label. It comes from identifying the exact legal question the treaty asks us to answer.
Three questions for advisers
- What rights does the immediate recipient actually hold?
- Which constraints arise from law, contract or commercial reality?
- Is beneficial ownership the correct doctrinal tool for the alleged abuse?
The result is a more disciplined analysis that separates entitlement to income from broader anti-avoidance arguments.
Michał Osiński
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Tester
By pof_master · July 27, 2026 · 1 min read
Related insights
The improper use of tax treaties, three decades on
Revisiting the doctrine that defined a generation of treaty interpretation.
Beneficial ownership and the limits of the treaty-abuse doctrine
As apex courts converge on the meaning of beneficial ownership, the doctrine of treaty abuse is being redrawn.
Ullamco dolor sit consequat ea dolore
Labore adipiscing voluptate ut commodo nostrud do ad exercitation consequat enim sit ex aute nisi reprehenderit lorem aliqua et amet ea adipiscing magna ad eiusmod commodo voluptate ex quis sed incididunt aute aute tempor laboris ut et do aliqua aute aute laboris. Et minim velit irure ex labore do s…
Dedicated expertise
Clarity where tax law meets international disputes
A focused opening section for a landing page, a service page or an in-depth explanation of a complex legal issue.
Strategic perspective
Independent analysis for decisions that carry weight
The same opening structure on an inverse surface, suited to campaign pages and high-impact topic introductions.

International tax advice
International tax analysis in its full legal context
We connect treaty interpretation with investment law, commercial reality and the wider policy environment.
Use it to explain a service, introduce an expert or give context to a key issue without losing the visual rhythm of the page.
View key benefits →
Expert-led engagement
Reverse the composition without changing its proportions
Direct access to senior experts keeps complex questions focused, independent and practical.
- Independent and conflict-free perspective
- Academic depth translated into practical advice
- Direct access to the engaged expert
Dark overlay · bottom left
Tax and treaty questions rarely exist in isolation
Use a strong photographic or abstract background while maintaining controlled contrast and readable measure.
Explore the issue →Light overlay · centred
A quieter editorial variation
Suitable for publications, research themes and pages where the image should remain present without overpowering the content.
Read the analysisWays we can help
A focused offer, clearly structured
Three focused forms of engagement, shaped around the legal question and the decision it must support.
Independent expert opinion
A reasoned, conflict-free view on a defined treaty, directive or anti-avoidance question.
- Written opinion
- Peer review
- Board-level briefing
Dispute and arbitration support
Tax analysis designed to withstand scrutiny before tribunals, courts and counterparties.
- Expert reports
- Hearing preparation
- Cross-examination support
Strategic policy advisory
Testing policy choices against international law, economic reality and geopolitical developments.
- Policy design
- Risk review
- Stakeholder briefing
Why this approach
The value is in the combination
For questions that cross doctrinal borders, the quality of the answer depends on seeing the whole legal and policy environment.
Conflict-free independence
Advice shaped by the issue itself, not by a broader institutional relationship.
Direct senior attention
The expert you engage remains personally responsible for the analysis.
Cross-disciplinary range
Tax, treaty, arbitration and policy considered as one connected field.
Clear practical output
Rigour translated into conclusions that decision-makers can use.
Selected evidence
Credibility expressed with restraint
Selected indicators of experience across scholarship, policy, controversy and cross-border advisory work.
A direct working model
From first question to usable conclusion
A direct working model with clear responsibility, scope and communication from the first exchange.
- 01
Initial review
We assess the issue, conflicts and the most useful form of engagement.
- 02
Scope & materials
Questions, assumptions, documents and timing are defined precisely.
- 03
Analysis
Law, evidence and policy context are tested as an integrated whole.
- 04
Delivery
Conclusions are presented clearly, with direct access for follow-up.
Representative matter · Anonymised
€1bn+Cross-border dividend flow under reviewTreaty abuse & beneficial ownership
A narrow question with consequences across several legal systems
Independent analysis addressed the relationship between beneficial ownership, domestic anti-abuse rules and the applicable treaty framework.
- Role
- Independent expert report
- Forum
- Administrative court proceedings
- Scope
- European Union · Treaty network

“The strongest opinion is not the longest one. It is the one that makes every decisive assumption visible.”
“Their independence gave the board a clear view of both the technical merits and the policy risk.”
Choose the right depth
Engagement models
The form of engagement follows the depth, timing and decision-making context of the matter.
Expert review
For a defined question or an existing position that requires independent scrutiny.
- Document review
- Written observations
- One review session
Independent opinion
For a matter requiring original analysis, documented reasoning and direct expert access.
- Defined research scope
- Reasoned written opinion
- Presentation and follow-up
Strategic advisory
For policy development, complex proceedings or a sequence of connected decisions.
- Continuing availability
- Scenario testing
- Stakeholder briefings
Practical questions
Before an engagement begins
Practical answers on independence, confidentiality and how a cross-border engagement begins.
Is Van Weeghel & Kuźniacki a law firm?
No. It is an independent expert platform operating on a barrister-type model. The Founders engage individually or jointly depending on the matter.
Can you act alongside existing legal counsel?
Yes. Engagements are designed to complement counsel, internal tax teams, boards, governments and international organisations.
How is confidentiality handled?
Conflict and confidentiality arrangements are agreed before substantive materials are reviewed. Do not send confidential information with an initial inquiry.
Do you accept cross-border matters?
Yes. The model is remote-first and designed for matters spanning jurisdictions, institutions and legal disciplines.
What happens after an initial inquiry?
We respond personally, assess conflicts and fit, and propose a clear scope where the matter falls within our expertise.
Related publication
Need the full analytical framework?
Pair a dedicated topic page with a paper, briefing note or case-law collection.
Discuss the issue
Bring us the difficult question
We will tell you promptly and candidly whether and how our expertise can help.
Executive summary
The issue at a glance
The decisive points for counsel and decision-makers before the full analysis begins.
- 01
Start with the legal function
Beneficial ownership should answer the treaty question actually before the decision-maker.
- 02
Separate entitlement from abuse
Economic control, legal rights and anti-avoidance analysis are connected but not interchangeable.
- 03
Test the full factual record
Contracts, governance and commercial context matter more than labels attached to an entity.
Lead expert · International Tax
Prof. dr. Stef van Weeghel
Professor, counsel and expert witness combining treaty analysis with decades of frontline practice.
Lead expert · Tax & Technology
Błażej Kuźniacki, Ph.D., Hab.
Independent expert on beneficial ownership, abuse, GAAR, CFC regimes and tax administration.
Research materials
Primary sources and further reading
A structured resource list for legal sources, judgments, reports, publications and downloadable documents.12
OECD Model Tax Convention
Articles, Commentary and historical materials relevant to beneficial ownership.
Selected apex-court judgments
A cross-jurisdiction collection with concise notes on reasoning and practical relevance.
Beneficial ownership: analytical framework
A concise working paper for counsel, boards and tax teams.
Academic & institutional ecosystem
Experience recognised across institutions
Continue exploring
Related analysis
The improper use of tax treaties, three decades on
Revisiting the doctrine that defined a generation of treaty interpretation.
Read Article →Beneficial ownership and the limits of the treaty-abuse doctrine
As apex courts converge on the meaning of beneficial ownership, the doctrine of treaty abuse is being redrawn.
Read Article →Ullamco dolor sit consequat ea dolore
Labore adipiscing voluptate ut commodo nostrud do ad exercitation consequat enim sit ex aute nisi reprehenderit lorem aliqua et amet ea adipiscing magna ad eiusmod commodo voluptate ex quis sed incididunt aute aute tempor laboris ut et do aliqua aute aute laboris. Et minim velit irure ex labore do s…
Read Article →
Investment arbitration
Tax questions rarely stay within one legal system
We connect international tax analysis with treaty, investment and commercial context to give counsel a coherent position.
Discuss the issue
Independent expert platform
Senior expertise, engaged without institutional conflicts
The Founders work directly with counsel, boards, governments and international organisations on the questions that matter.
Meet the experts →
Cross-border tax law
A single issue can carry consequences across jurisdictions
Comparative legal analysis reveals where national approaches converge, conflict and create strategic risk.
Explore sources

Strategic perspective
Independent judgment for questions that carry weight
Clear conclusions begin with a precise view of the law, facts and policy context.
Continue →Global tax policy
Policy advice grounded in law and geopolitical reality
We help institutions test proposals against international obligations and practical consequences.
See the processJoint expertise
Two disciplines. One direction.
Scholarly precision and frontline pragmatism, brought together for complex cross-border matters.
Start a conversation