Acknowledgements
Ever since we met as judicial fellows at the International Court of Justice over a decade ago, we have wanted to embark upon a research project together. The opportunity finally presented itself when, in conversation, we came across a topic that not only felt timeless and timely but also provided an ideal intersection for our current intellectual interests: the question of the applicability of customary international law to, and within, the European Union. We then gathered a group of scholars who are experts both in international law and in EU law in Alcalá de Henares for a wonderfully stimulating and convivial workshop in October 2018. Seeing as the contributions prepared for and discussed at the workshop offered insightful and durable reflections of both theoretical and practical relevance, the publication of an edited volume seemed like the logical next step.
We wish to extend our gratitude to Lukas Baumgartner, Alice Falkner and Theresa M. Weiskopf (University of Innsbruck) for their invaluable assistance during the editing process of the book. We owe a debt also to Laura Aragonés-Molina for her cooperation in the organization of the workshop held at the University of Alcalá, and to Tom Randall, our editor at Cambridge University Press, whose support and encouragement are greatly appreciated. Last but not least, this book is part of a project that benefitted from the generous support of the European Commission through the Erasmus+ programme.
