Table Of Contenti
MODIFICATION OF TREATIES
BY SUBSEQUENT PRACTICE
Modification of Treaties by Subsequent Practice. Irina Buga. © Irina Buga, 2018. Published 2018 by
Oxford University Press.
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Modification of Treaties
by Subsequent Practice
IRINA BUGA
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To my parents, grandparents, and Mike
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Foreword
If the States Parties to a treaty issue a statement of their common understanding of a
treaty provision, how can we know if they are interpreting the treaty or amending it?
If they make no statement, but one of them does something in relation to the subject
matter of the treaty and the other makes no objection or other comment, does that
practice evidence a common understanding of the treaty? If the treaty is amended,
is it the same treaty as it was before, or a new treaty which came into existence when
the original was amended? What if the treaty is one that, like bilateral investment
treaties, appears to create rights for individuals? What if the practice is not that of
States Parties but of other States, establishing new rules of customary international
law, or consisting of resolutions adopted by majority votes in organs of international
organizations? These are the kinds of question that tax even the most astute ana-
lytical lawyers. Indeed, some of the questions are more like a Buddhist koan than a
soluble legal problem. And yet these are questions that are faced day in and day out
by practising international lawyers.
Most legal monographs would map out the field of established treaty law and
work cautiously towards problems such as these. But this masterly study starts with
the problems and tackles them head on. It does so against the background of the
work of the International Law Commission on subsequent agreements and subse-
quent practice in relation to the interpretation of treaties. Combining precise ana-
lysis with robust digging into the mass of State practice and international case law,
Dr Buga’s text makes a major contribution to the analysis of this most subtle and
most important set of questions. It both clarifies the problems and, brimming with
ideas, stimulates thought.
Sophisticated and immensely accomplished, her study discerns differences in the
approaches that are adopted to these problems in different fields, such as inter-
national human rights and WTO law. Focusing on the value of interpretation and
modification as sources of stability in international relations, which secure the adap-
tation and organic development of international law, she has produced a lucid and
principled framework for handling these crucial questions.
Vaughan Lowe
London, 2017
Modification of Treaties by Subsequent Practice. Irina Buga. © Irina Buga, 2018. Published 2018 by
Oxford University Press.
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Acknowledgments
There are so many people to whom I am grateful and indebted for their support,
guidance, and friendship throughout the writing of this book. Though it seems im-
possible to give them the credit they deserve by means of a few, short sentences, I will
try nevertheless.
I must begin by thanking my PhD supervisors, Professor Alfred Soons and
Professor Alex Oude Elferink, without whom the initial project that led to this book
would not have come to fruition. They answered my ceaseless questions with pa-
tience and insight, and provided guidance and sparring sessions throughout the en-
deavour. I am likewise grateful to the members of the Doctoral Thesis Committee,
Professor Cedric Ryngaert, Professor Liesbeth Lijnzaad, Professor Ige Dekker,
Professor André Nollkaemper, and Dr. Catherine Brölmann.
My deep appreciation goes to the colleagues and legal scholars whose advice and
feedback have helped steer this project forward and shaped my ideas, particularly
Professor Georg Nolte, whose work on the topic in the context of the International
Law Commission has been a source of inspiration and whose advice on my earlier
work was highly valuable; Seline Trevisanut and Ingo Venzke, for dealing with my
many queries; my former colleagues at the Netherlands Institute for the Law of the
Sea, for their enthusiasm and interest; and the Public International Law Department
of Utrecht University in general, for the truly enriching experience. Moreover, my
gratitude goes out to the members of the Royal Netherlands Society for International
Law (KNVIR) for their appreciation of my research with the François Research
Prize, and the Netherlands Organization for Scientific Research (NWO) for their
generous funding of my doctoral work. I would also like to kindly thank my OUP
editors and anonymous reviewers.
The years spent in Utrecht and Oxford, at the International Court of Justice in
The Hague, and practicing arbitration in Paris and Amsterdam, have all contributed
in important ways to my personal development and the gradual development of
this book. I am generally indebted to the inspiring people who have expanded my
knowledge and understanding of international law over these years. To name only
a few, I would like to express my deep gratitude to Professor Vaughan Lowe, for
his supervision and invaluable insight into international dispute settlement during
my studies at the University of Oxford, to Mr. Philippe Couvreur, for his words of
wisdom and motivation during my time at the International Court of Justice, and
to Professor Leonard Besselink and Professor Ewoud Hondius, for their guidance
and encouragement during the Legal Research programme. I would also like to
thank Professor Kees Roelofsen, whose International Law course during my under-
graduate studies first introduced me to this fascinating field.
Now in Amsterdam, I must thank my brilliant colleagues at De Brauw Blackstone
Westbroek, who constantly challenge me to sharpen my thinking as well as my
writing. In particular, I am grateful to the talented international arbitration group
Modification of Treaties by Subsequent Practice. Irina Buga. © Irina Buga, 2018. Published 2018 by
Oxford University Press.
x
x Acknowledgments
and to Marc Ynzonides for all the encouragement, and to ‘Brauwerij XXI’ for their
support and poking fun when I needed it.
My friends have been amazing during this entire process. Special thanks go out
to, in no particular order, Stef, Paulette, Masha, Inge, Romi, Nate, Philip, Sandi,
Anna, Sibel, Gala, Andrea, Selma, Mistale, Luke, Marli, Erik, Charlotte, Andrew,
Sebastiaan, Micky, Hein- Jan, Eveline, Linda, and many others, for providing much-
needed support – and distraction.
As for my parents, Mihaela and Iulian, two of the most amazing people I know,
I cannot begin to thank them for their infinite support and pep talks, and for in-
voluntarily becoming ‘experts’ on subsequent practice over the years. This work
is dedicated to them, to my grandmother Maria, for always believing in me and
sharing her wisdom and anecdotes, and to my grandparents Constantin, Ernestina,
and Jacques, who I wish could still be here today.
Last but certainly not least, I cannot imagine having written this book without
the love, support, and unwavering patience of Mike Blommestijn.
Amsterdam, December 2017
