This book sprang from a somewhat different intellectual exercise. In 2009, working as member of a newly established transnational group of public lawyers (the Research Network on EU Administrative Law – ReNEUAL), I began to reflect on the different European traditions of public law with a view to ascertaining whether – on the basis of comparative research – there were some best practices that could be used to reinforce the general principles of European Union law. The comparative analysis carried out proved to be a useful tool, and we published the ‘model rules’ for EU administrative procedure, raising discussion about their reform.

However, the more the group compared the national rules and practices, looking at the various circumstances where its proposals were debated in diverse corners of Europe, the more it became evident that there were sometimes real differences hidden behind a façade of apparent similarities, for example with regard to fairness and openness. Conversely, different legal systems often reached the same results via different ways of engaging with the relationship between norms and exceptions, as formulated by jurists and judges. The duty to give reasons was an instructive example. It thus became evident that some ideas and beliefs about public law – and law itself – such as the existence of a sharp divide between civil law and common law or a single model of administrative courts were not simply unable to make sense of the legal institutions of our time but were also unsound with regard to the past. The birth and development of our public law traditions, the interplay between commonality and diversity, the emergence of shared general principles of administrative law could not be illustrated by those received ideas. I expressed these remarks in an article published in English and German, but I was aware that this first attempt had not dealt with the problem of how we should address some of the basic theoretical questions.

In this respect, the experience gathered through that inspiring transnational group also showed the limits of traditional comparative approaches based on legislative design. The increasing volume of material that emerged from national studies called for a different methodology. I tried to ascertain whether this material could be better understood through a ‘factual analysis’ based on hypothetical cases, already experienced in the field of private law. Through this methodology, issues that had all too frequently been taken for granted in public law texts (such as whether an individual must be afforded a meaningful opportunity to be heard before an adverse decision is taken by a public authority) must be addressed critically, also in the light of underlying theories. Some adjustments were necessary, however, due to the distinctive features of public law, including the judicial construction of general principles, the legal relevance of government practices, and the impact of new constitutional provisions. Moreover, the previous doubts cast on the reliability of some less recent views on public law reinforced the conviction that only a combination of history and legal comparison could provide the gauge for reflecting on administrative laws in Europe.

The research project that began in 2016 was thus designed to analyze the ‘common core’ of European administrative laws through both diachronic and synchronic comparisons. Since a large number of experts were involved (almost 120 from thirty-four countries, not only from Europe) in the various lines of research, it may also be said that the new comparative research is a collective enterprise, differing however from the previous one insofar as it seeks to make sense of both shared and distinctive traits.

The financial backing for the entire project provided by the European Research Council must be acknowledged, as must the organizational support from Rome’s ‘Tor Vergata’ University and Bocconi University in Milan. Both universities allowed me to take periods of leave for research and study abroad. The Max Planck Institute for Comparative Public Law and International Law of Heidelberg and the University of Paris ii kindly hosted me during those absences, and several universities and research institutions (including the Law School of the ‘Pompeu Fabre’ University of Barcelona, the University of Cracow, the ‘Pazmany’ University of Budapest, the Institute of Advanced Legal Studies of London, and the Penn Carey Law School). In addition, the universities of Bologna, Ferrara, Florence, the Milan ‘Cattolica’, Palermo, the Rome ‘La Sapienza’, Trento, and Turin in Italy invited me to discuss the research methodology and results.

This book attempts to summarize some of the main results emerging from this comparative research and to construct a theory of the common core that reflects the legal history of Europe, suited to modern administrative States yet open to the influence of two regional organizations that have existed since the 1950’s, namely the Council of Europe and the European Community (now the EU). Whatever the success of the enterprise from the reader’s perspective, it has been made possible by the contribution of so many persons that it would be hard to mention all of them. Special thanks are owed to Mauro Bussani, my partner in this research, to Jean-Bernard Auby and Paul Craig, whose comments in the early days of the work brought me to the realization that these thoughts, if worth sharing, required a book distinct from the articles and volumes in which the various lines of research had been presented and, last but not least, to Gordon Anthony and Giulia Labriola, who made several comments on the manuscript. I am also indebted to Mads Andenas, Armin von Bogdandy, Allan Brewer-Carias, Roberto Caranta, Bruno De Witte, Luis Maria Dièz-Picazo, Carol Harlow, Stefano Mannoni, Marco Mazzamuto, Neysun Mahboubi, Thomas Perroud, Otto Pfersmann, Alec Stone Sweet, Aldo Travi, Ellen Vos, and Jacques Ziller for their comments, some of which were critical, others encouraging. Martina Conticelli, Angela Ferrari Zumbini, Marta Infantino, and Leonardo Parona have all contributed to diverse aspects of this comparative enquiry. To these and many others, I acknowledge a debt whose importance is not undermined by the fact that, of course, I alone am responsible for all errors or omissions. Adrian Bedford and Paola Monaco revised all the chapters from a linguistic point of view and on the basis of the Brill guidelines, respectively.

Finally, and most importantly, I am indebted to Simonetta, Isabella, Alfonso and Federico for their patience and encouragement during all these years.

Rome, 30 January 2023