Tax Treaty Interpretation in light of the Vienna Convention on the Law of Treaties


As part of its increased focus on tax certainty in the international dimension, IFA is currently working on a book on “Tax Treaty Interpretation in light of the Vienna Convention on the Law of Treaties”. This book will revisit the fundamental principles of interpretation of tax treaty law and will provide guidance in order to facilitate and strengthen the consistency of tax treaty practice with the principles laid down in the Vienna Convention on the Law of Treaties (VCLT).

The book will be published by IBFD. An update of the project will be presented at the 2023 Cancun Congress.

Chief editors


Prof. Dr. Robert Danon

Chairman of the Permanent Scientific Committee (PSC) of IFA

Robert Danon is a full Professor of Law at the University of Lausanne (Switzerland), where he heads its Tax Policy Center and leads its research platform dedicated to “Tax Disputes and Investment Arbitration”.
Next to his academic duties Professor Danon is a founder of DANON, an independent firm with a predominant emphasis on international tax disputes and international arbitration.
At the international level, his academic and practical expertise focus on international tax disputes with an emphasis on tax treaties and their interpretation, non-discrimination, abuse of rights by taxpayers and States, comparative taxation and transfer pricing.
He also concentrates on the interaction between investment arbitration and tax-related disputes.
Robert Danon is regularly called to give evidence as an expert witness or to act as counsel in the framework of domestic and foreign court proceedings, mutual agreement and arbitration procedures, including those involving bilateral investment treaties.
He has served as an expert witness in international tax law in several high-profile investment arbitration cases under the UNCITRAL and ICSID arbitration rules. He is on the list of possible arbitrators under the mandatory binding arbitration clauses provided by selected bilateral tax treaties.
Robert Danon has been involved in several tax reforms and assists both taxpayers and governments on tax policy matters. He has testified before Parliamentary Committees. For instance, in 2015, he was requested by Switzerland's finance minister to analyze the entire constitutionality of its corporate tax reform designed to comply with the OECD/G20 and EU standards.
Moreover, he is regularly invited by the OECD to express his views on matters of international tax law and policy. In particular, he has been invited on several occasions by the OECD to express his views on the challenges raised by the digitalization of the economy (“Pillar One”) and the introduction of a global minimum taxation regime (“Pillar Two”)
Robert Danon holds a PhD in Law (“doctorat en droit”) from the University of Geneva (“summa cum laude”) and an LL.M in International Taxation from the University of Leiden (the Netherlands).

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Prof. Dr. Adolfo Martín Jiménez

Vice-Chairman of the Permanent Scientific Committee (PSC) of IFA

Adolfo Martín Jiménez (Ph.D. European University Institute, Florence, Italy, 1997, LL.M. University of Wisconsin, 1995) is a Professor of Tax Law and was Jean Monnet Chair of the European Commission (‘EU tax law’) (2014-2018) at the University of Cadiz. He specializes in international taxation, including transfer pricing, and EU tax law and is the author of several books and more than one hundred articles on these subjects, in English and Spanish, published in several countries, and some translated into other languages (e.g. Chinese, Japanese).

He has extensive practical experience in international taxation, transfer pricing and EU tax law, frequently acting as a consultant for (1) multinational groups, (U) HNW individuals and professional firms with international activity; (2) tax administrations and states (in tax reforms, capacity building, application of international standards or supporting them in international lawsuits and controversies), and (3) international organizations relevant in the definition of international tax standards (e.g. in 2015-2019 he was a member of the EU Joint Transfer Pricing Forum). He has also appeared in Parliamentary Commissions of the central and autonomous State, or Parliaments of other countries. He frequently intervenes, as an independent expert, providing legal opinions in tax audits, rulings, MAPs or tax and investment arbitrations.

Adolfo regularly participates as a speaker in professional and academic international conferences all around the world on international taxation and EU tax law, and in courses and capacity building initiatives organized by Tax Administrations or judicial organizations in various countries. From 2018 to June 2022 he was the Chairman of the European Association of Tax Law Professors and since September 2022 he is Vice Chairman of the Permanent Scientific Committee of the International Fiscal Association.


In 2021, he was awarded by the IBFD the 7th Frans Vanistendael Award for outstanding international taxation research in 2020 for his work “Value Creation: A Guiding Light for the Interpretation of Tax Treaties?”, Bulletin for International Taxation 4/5 – 2020.

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Prof. Dr. Guglielmo Maisto

The President of Global IFA

Guglielmo Maisto, founded Maisto e Associati in 1991. He is a Professor of international and comparative tax law at the Università Cattolica di Piacenza. He isThe President of the International Fiscal Association (IFA) and President of the Italian IFA Branch, member of the Board of Trustees of the International Bureau of Fiscal Documentation (IBFD) in Amsterdam, member of the Practice Council of New York University (NYU) Law’s International Tax Program and member of the Board of the American Chamber of Commerce in Italy. He acted as a consultant to the Ministry for European Community Affairs and was a member of the EU Joint Transfer Pricing Forum. He is a member of several law societies and of the editorial board of various Italian and foreign tax legal journals. He usually participates as speaker to several annual tax conferences.

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Authors / Contributors

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Prof. Dr. Pasquale Pistone

Academic Chairman of IBFD. Full Professor of Tax Law at the University of Salerno and Holder of a Jean Monnet ad Personam Chair in European Tax Law and Policy at WU Vienna.

Honorary Professor at the Ural State Law University (Russia) and at the University of Cape Town (South Africa). Honorary Doctor at the University of Örebro (Sweden). Visiting Professor (2022/2023) at the NYU School of Law.

Chief editor of the journals World Tax Journal and of ITAXS, the IBFD Doctoral Series and the Series of International Tax Law by Bloomsbury and of the IBFD Global Tax Treaty Commentaries. Co-editor of the journal Diritto e Pratica Tributaria Internazionale. Editor and author of numerous books, articles and book chapters, published and/or translated in 12 languages, on international and European tax law, which are his core research areas.

Secretary General of the European Association of Tax Law Professors. Co-Chair of the Tax Committee of the International Law Association. Member of the Permanent Scientific Committee of the International Fiscal Association.

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Dr. Katerina Perrou

Dr. Katerina Perrou is a Lawyer, and Post-doctoral Fellow and Assistant Lecturer in Tax Law at the Law School of the National and Kapodistrian University of Athens. She has studies in Athens (bachelor’s degree and LLM in Public Law) and in London, where she completed her PhD on “Taxpayer Participation in Tax Treaty Dispute Resolution” at the Institute of Advanced Legal Studies, University of London, UK. 

In 2016-2018 she joined the IBFD, Amsterdam, the Netherlands, as postdoctoral research fellow on Tax Treaty Issues.

She is the Secretary General of the Greek IFA Branch.

Currently, she serves as Legal Counsel to the Governor of the Greek Independent Authority for Public Revenue.

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Prof. Dr. Stef van Weeghel

Prof. Dr. Stef van Weeghel is Global Tax Policy leader at PwC, professor of international tax law at the University of Amsterdam and chair of the Board of Trustees at IBFD. Before he joined PwC in 2009 he was partner at law firms Stibbe and Linklaters, where he practiced in Amsterdam and New York.  
His focus is on tax policy and tax controversy, with research covering tax treaties and investment treaties. He regularly acts as expert-witness or co-counsel in tax disputes and in investment treaty and commercial arbitration. He is consulted by the private sector and governments, chaired a government-appointed Dutch tax reform committee, appeared before both chambers of the Dutch Parliament and the TAXE and PANA Committees of the European Parliament. He is immediate past chair of the PSC of IFA, an honorary member, has acted as IFA branch and general reporter, as chair of the IFA-OECD Seminar, and as secretary and chair of the Dutch branch of IFA. He authored and co-authored several books and numerous articles on Dutch and international taxation and has lectured extensively. He received his law degree from the University of Leiden (1983), was admitted to the Amsterdam Bar (1987), obtained an LL.M. in Taxation from NYU (1990) and received a doctorate in law from the University of Amsterdam (1997).

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Prof. Alexander Rust

Alexander Rust is Professor of International Tax Law at Wirtschaftsuniversität Wien and Director of the Master Program Digitalization and Tax Law. Before joining the Institute of Austrian and International Tax Law Alexander Rust held positions as Acting Assistant Professor in the International Tax Program at New York University and as Professor of Tax Law and Director of the Master Program in European and International Tax Law at the University of Luxembourg. He specializes in all areas of tax law but is also fascinated by constitutional and European law. He is a frequent guest lecturer at universities in and outside Europe.

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Prof. Daniel Gutmann

Daniel Gutmann is professor of domestic, international and european tax law at the Sorbonne Law School (University Paris-1) where he is the Director of a research centre in taxation (Sorbonne-Fiscalité-Finances Publiques). He wrote numerous articles in tax matters and is the author of a book on taxation of businesses (Droit fiscal des affaires, Lextenso, 13th ed., 2022) which was awarded the Legal Book Special Prize by the French Constitutional Court and the “Club des Juristes”. He has also published a book on the methodology of tax law interpretation (Sources et ressources de l’interprétation juridique. Etude de droit fiscal, Lextenso, 2023).

He is also a partner at CMS Francis Lefebvre Avocats, in charge of the Tax Intelligence Department. Within CMS, Daniel is the Head of the CMS Treaty and EU Tax Law Group and a member of the steering committee, CMS Global Tax.

Beyond his activities at University and CMS, Daniel is the Scientific Director of “Fiscalité internationale”, a French tax review dedicated to international tax law.

He is the Chairman of the Academic Committee of the European Association of Tax Law Professors (EATLP), a member of the Permanent Scientific Committee of IFA and of the Scientific Committee of the French IFA Branch.

Until 2020, he was a member of the “Conseil des prélèvements obligatoires” (the French Tax and Social Charges Board).

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Prof. Craig Elliffe

Craig is a Professor of Taxation and Law at the University of Auckland, Faculty of Law. Before taking a chair he was for 14 years a tax partner at KPMG and for eight years subsequently a tax partner at Chapman Tripp. His research areas are particularly in tax avoidance, international tax and corporate tax. He is the Director of the University of Auckland’s Master of Taxation Studies programme and he has written extensively on tax issues. Craig is a member of the Tax Advisory Group of Chartered Accountants in Australia and New Zealand, the tax committee of CPA Australia, and was a member of the Permanent Scientific Committee of the International Fiscal Association and the New Zealand Government’s Tax Working Group (2018-2019). He is the author of a number of journal articles in publications such as the British Tax ReviewCanadian Tax JournalAustralian Tax Forum, World Tax Journal, and the New Zealand Universities Law Journal and has authored the JF Northey prize winning book International and Cross-Border Taxation in New Zealand published by Thomson Reuters (2015 and 2018), and Taxing the Digital Economy: Theory, Policy and Practice, Cambridge University Press (2021). 

BCom, LLB (Hons), LLM (Camb), PhD (Camb), FCA

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Prof. Sjoerd Douma

Sjoerd Douma is Professor of International & EU Procedural Tax Law at the University of Amsterdam and Partner at Lubbers, Boer & Douma in The Hague. Prior to his appointment in October 2017, he was a professor at Leiden University. Sjoerd is a member of the Permanent Scientific Committee of the International Fiscal Association. He has specialized in corporate income taxation, tax treaties, European tax law and procedural law. Sjoerd has been a Deputy Judge in the Court of Appeals of Arnhem-Leeuwarden, a Deputy Judge in the District Court of Haarlem and Visiting Professor at Université Panthéon-Assas (Paris, France). He is a permanent contributor to leading Dutch and international tax journals. He has authored and co-authored numerous publications and reports on national, international and European tax law. Prior to joining Lubbers, Boer & Douma in March 2017, Sjoerd has practiced tax law at one of the ‘big four’ tax advisory firms. Sjoerd has represented taxpayers before the tax authorities, the Dutch tax courts (including the Dutch Supreme Court), the European Commission and the Court of Justice of the European Union.

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Prof. Scott Wilkie

Scott Wilkie is a Research Fellow of the Amsterdam Centre for Transfer Pricing and Income Allocation, part of the Amsterdam Center for Tax Law of the University of Amsterdam, a recently retired Distinguished Professor of Practice at Osgoode Hall Law School, York University, and a retired partner of and senior counsel to Blake, Cassels & Graydon LLP. Widely published, he speaks and writes broadly about taxation, notably international taxation and tax policy. He is a former vice-chair of the Permanent Scientific Committee of the International Fiscal Association, served as president of the Canadian branch of the International Fiscal Association, and is a past chair of the Canadian Tax Foundation.

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Prof. Dr. Dr. h.c. Michael Lang

Prof. Dr. Dr. h.c. Michael Lang is Vice Rector Research and Human Resources of WU, Head of the Institute for Austrian and International Tax Law of WU (Vienna University of Economics and Business) and Academic Director of both the LL.M. Program in International Tax Law and of the doctoral program in international business taxation (DIBT) of this university. He is President of the Austrian Branch of the International Fiscal Association  (IFA).

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John Avery Jones

John Avery Jones is a retired Judge of the UK Upper Tribunal (Tax and Chancery Chamber).

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Jean-Blaise Eckert

Jean-Blaise Eckert, Secretary General of IFA, is a partner at Lenz & Staehelin and co-head of the tax group. His practice areas include tax, private clients, contract law and commercial.

He speaks French, English and German. Jean-Blaise studied law at the University of Neuchâtel and was admitted to the Bar of Neuchâtel in 1989 and to the Bar of Geneva in 1991. He studied business administration at Berkeley, Haas Business School, where he acquired an MBA in 1991. He received his diploma as a Certified Tax Expert in 1994 and is a Certified Specialist in Inheritance Law.

Jean-Blaise is considered as a leading lawyer in Switzerland. He advises a number of multinational groups of companies as well as HNWIs. He sits on the board of a number of public and private companies. Jean-Blaise is a frequent speaker at professional conferences on tax matters. Jean-Blaise is Secretary General of the International Fiscal Association (IFA).

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Bruno Gibert

Bruno Gibert joined CMS Francis Lefebvre Avocats as an equity partner in 2001. He specializes in international taxation with a particular focus on transfer pricing matters. On this last domain, he heads the transfer pricing group the CMS network has put in place within the tax practice. He has 16 years' experience in the government service, where he was in charge of international tax affairs (negotiation of tax treaties with foreign countries, OECD and EU work, and competent authority). He used to be co-chairman of the OECD forum on harmful tax practices (1996-2001). He was also Chairman of the EU joint forum on transfer pricing from 2002 to 2019. He has been appointed as an independent person of standing for the EU Arbitration Convention and the EU Directive on Dispute Resolution. Former chair of the International Fiscal Association (IFA) French branch, he is also a member of the board of trustees of the International Bureau of Fiscal Documentation (IBFD). Author or co-author of several books on international tax matters, he regularly publishes articles on these matters in French and international publications.

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Prof. Johann Hattingh

Johann Hattingh is Professor in the Department of Commercial Law at the University of Cape Town, South Africa. His PhD thesis, awarded by the University of Cambridge, formulated an integrative theory for tax treaty interpretation. He holds two LLM degrees, one from the University of Cape Town and the other from Leiden University in the Netherlands. He obtained B.Com (Law) and LL.B degrees from Stellenbosch University. Since 2003 he holds an association with the International Bureau of Fiscal Documentation (IBFD) in Amsterdam, where in 2019 he took up the Chief Editorship of the Bulletin for International Taxation

Professor Hattingh has given lectures and seminars at the International Tax Centre of Leiden University, Stellenbosch University, the University of Cambridge, the Institute for European and Comparative Law at the University of Oxford and the Institute of Austrian and International Tax Law at Vienna University of Business and Economics. At the University of Cape Town, he convenes Africa’s only master’s degree programme fully devoted to interdisciplinary study of international taxation. He has acted as senior international consultant for the UN Economic Commission for Africa, the International Monetary Fund, and participated in the tax work of NEPAD on behalf of the African Union. He is regularly consulted by public and private sector organisations across Africa.  His professional memberships include the International Tax Group, the International Tax Law Committee of the International Law Association and the permanent scientific committee of the International Fiscal Association.

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Chloe Burnett

Chloe Burnett SC is a tax barrister based in Sydney, Australia.  She has appeared in a number of significant international and corporate tax cases.  She is the Vice-President of the Australian Branch of IFA.  In the period 2018 to 2020 she was the Chair of the Recent Developments Panel at the IFA Congress.  Chloe studied law, finance and accounting as an undergraduate at Sydney University and she has a LLM from New York University.  Chloe lectures in Interpretation of Statutes, Contracts and Treaties in the LLM program at The Sydney Law School, and regularly publishes articles on international and corporate tax and on legal interpretation.  Before becoming a barrister, Chloe was a solicitor at Allens and worked as an Associate to the Honourable Justice Edmonds of the Federal Court.  She has also worked for Macquarie Bank in Sydney and Slaughter and May in London.

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Jennifer Davies

The Hon Jennifer Davies S.C. is a retired judge of the Federal Court of Australia and during her time on the bench was the national co-ordinating judge of the Taxation National Practice Area. Prior to her appointment to the Federal Court she was a judge of the Supreme Court of Victoria, sitting in the Commercial Court division and before then, a member of the Bar from May 1983. She took silk in 2004.

She is an Honorary Principal Fellow at the University of Melbourne lecturing in postgraduate courses and on the Melbourne University Tax Advisory board. She is also on the board of the International Association of Tax Judges and is a member of the Australian Academy of Law, the International Academy of Estate and Trust Law and the International Fiscal Association, and a Fellow of the Taxation Institute of Australia.

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