At the very outset, I would like to say a few words concerning the book’s structure1 and purposes.2 First of all, the book provides a sketch of public international law’s main principles and fundamental institutions. It aims at introducing the reader to the legal reasoning of public international law and enables the forging of the tools that any international lawyer should possess, whatever be his specific field: law of the sea, international human rights law (HR), space law, international humanitarian law (IHL), international labour law, international health law, the use of force, etc.3 Hence, we will deal with what has been called the “Institutes”4 of public international law (hereinafter PIL), which, being fundamental to the legal order, constitutes its grammar. Furthermore, strategic choices have been made with respect to what to deal with in a general and introductory work on public international law. That is why, unsurprisingly, the legitimate criticism could be made that the book does not, or does not sufficiently, discuss this or that particular theme. The book, thus, does not aim to be a comprehensive treatise, since it does not pretend at all to cover all the branches of PIL. Instead, drawing inspiration from Italian doctrine, we would like to consider it as “Lessons on Public International Law”, as in fact they originally were, destined to university students and practitioners alike.

A few words must be said concerning the general approach pervading the book. In this connection, the reader will not fail to notice extensive recourse to non English-speaking literature, as well as to less recent doctrine. Three main reasons are at the root of this methodology. First, this jurisprudence makes up my genetic imprint; and it would have been treacherous to, as it were, “hide the grass I grazed in”. Borrowing Bernard de Chartres’s famous statement, I am very proud of standing on “giants’ shoulders”; that is to say, my maîtres-à-penser, who have in one way or another determined my lifelong passion for this métier, and have thereby influenced my reflections.

The second reason – regarding non-English-speaking literature – rests with the intrinsic specificities of this field of jurisprudence, since I wish to bridge the gap between different concepts and schools of PIL worldwide. Our science belongs to the entire world, so that no section of it can pretend, especially nowadays, to appropriate it. PIL is perhaps the only branch of positive legal science which pertains to mankind as a whole; and this is not only a matter of language, since, as everyone knows, it involves the most intimate expressions of a culture, concerning the very way we reason and articulate our thoughts, not to mention the specific values each civilization aims to defend and to bring into legal existence.

The third reason pertains to my choice to rely, alongside contemporary doctrine, on the classics of PIL, and on less recent jurisprudence, which has a left a lasting legacy on today’s legal thinking.

International law is surely not a discipline that one can approach lightly. It is, nevertheless, neither difficult nor impossible. It is characterized by a well-marked frame of mind: a way of thinking that differs from other disciplines and assuredly, at least partially, from other provinces of the law, while yet sharing its core concepts and tools. Metaphorically speaking, PIL is to law what Formula 1 is to ordinary car racing.

Before even approaching international relations, the importance of international law must be underlined in order to grasp the notion. Could one imagine a society without law? Law is consubstantial to any society or man-made organization: law and society are thus indivisible. A society without law or law without a society is simply inconceivable. Both realities, which ultimately form an indivisible whole, do not cease continually to shape each other reciprocally.5 As the Latin saying goes, “ubi societas ibi ius”.6 Therefore, law appears as a windmill, the blades of which are moved by the winds of the Society. Yet, while it is possible to analyse international relations in many ways, whether historical, political, economic, ideological, geostrategic, military, etc., our perspective will strictly focus on legal analysis. Indeed, the observing lenses will consist of legal rules and concepts elaborated by jurisprudence in order to grasp the social phenomena.7

At last, the unavoidable part dedicated to the acknowledgements must be addressed. A so undisciplined scholar, as I am, has had two fathers who in turns have sparked my passion for International Law, thus diverting me from my original penchant for History. Professors Luigi Condorelli and Georges Abi-Saab have respectively instilled the pleasure for legal dexterity (and a welcome bit of sprezzatura) and the need for grasping Law as a system. These two beacons have since then provided a reassuring guidance. I am heartfelt indebted to them; they have, involuntarily, steered the course of my life tout court.

Since then, I have accumulated more intellectual debts that I can possibly repay. Indeed, I had the chance to be acquainted with lots of scholars and colleagues, beautiful peoples with whom I spent years refashioning the World and railing against those who dared to demean our beloved province of jurisprudence. International law, being, as everybody knows a “self-contained régime” (…), most of these peoples have become since then my friends, an unexpected and savory collateral damage. Thus, I am grateful to: Laurence Boisson de Chazournes, Santiago Villalpando, Jean-François Quéguiner, Robert Kolb, Petros Mavroidis, Nino Alì, Gloria Gaggioli, Drazen Petrovic, Makane Mbengue, Sébastien Touzé, Théo Boutruche.

In the same vein, my two assistants (in turns) at the Faculty of Law in Neuchâtel have demonstrated that Vattel’s ghost still haunts benevolently my Law students, straying them from the quaint destiny of law firms and catapulting them in the perilous path of International Law. I am thus proud, as only a Doktorvater can be, of Dr. Etienne Henry and Mr. Aymeric Hêche. They have given a concrete meaning to my daily labour. I am obviously grateful to Professor Malgosia Fitzmaurice for having kindly and immediately accepted my manuscript to be published in this prestigious series. In the same vein, my heartfelt gratitude goes to Ms. Ingeborg Van Der Laan for her infatigable efforts during the edition process.

Last, but not the least, I am indebted to the thousands of students who had to struggle attending my seminars and courses. They have, again involuntarily, made me aware that research and teaching nurture reciprocally and cannot be disentangled. I am therefore profoundly indebted to them and to their patience, questions and doubts which have pushed me to better understand the role of International Law in International Relations.

I consider myself very fortunate in having had my manuscript reviewed in turn by Ms. Kate Elliott (Chapters 3–8) and Sir Maurice Fitzmaurice (Chapters 1–2) who ventured to take up this fastidious challenge. My heartfelt gratitude is here expressed to them. In this connection, one my valiant Ph.D. students, Mr. Franck Some, was kind enough to prepare the indexes of this book while at the same time enduring the painstaking task of cleaning up the footnotes.

According to the usual disclaimer warning, all these peoples are responsible for the good things that the reader may happen to find in this book, while I am definitely the only culprit (no joint criminal entreprise applies here) for the misfits, errors, inaccuracies and other flaws that nonetheless still affect it.

This book is dedicated to my family: Christiane, my wife, my children, Mariagloria and Dionisio, my mamma, Nuccia, and to the loving memory of my papà, Alfio.

Mies, 4 December 2018


From the very outset, I am proud to acknowledge that the structure of this Course is inspired by the teaching of Professor Luigi Condorelli – of whom I have been in turns a student and assistant at the University of Geneva. I am thus profoundly indebted to Maestro Luigi both on the personal and scientific plane.


This volume constitutes the distillation of several teachings delivered throughout more than twenty years to students of different levels (BA, LL.M) and curricula (Law, International Relations, Political Science). It is in fact an introductory course originally conceived and eventually framed for an oral teaching, thus retaining, perhaps, its congenital flaws.


“What once appeared to be governed by “general international law” has become the field of operation for such specialist systems as “trade law”, “human rights law”, “environmental law”, “law of the sea”, “European law” and even such highly specialized forms of knowledge as “investment law” or “international refugee law”, etc. – each possessing their own principles and institutions”, Fragmentation of international law: difficulties arising from the diversification and expansion of international law: Report of the Study Group of the International Law Commission (A/CN.4/L.702, 28 July 2006, § 6, pp. 3–4). However, beyond its specificities – taking into account mainly material law – these different fields share – unavoidably so – the same rules of proceedings and functioning of the system, as well as some peremptory norms of PIL (ius cogens) that will be the object of discussion further (infraV.1.2).


“I have adopted the terms ‘Institutes of Law’ … in order to indicate the fundamental relation in which the subject stands to all the departments of positive law”, J. Lorimer, Institutes of Law, Edinburgh, 1880, p. 4. The same author entitled another of his works (The Institutes of the Law of Nations: A Treatise of the Jural Relations between Separate Political Communities; London, 1883–1884). More generally, as it is widely admitted, this term is meant as a set of rules and principles that relate to a specific phenomenon. As the Black’s Law Dictionary (6th ed., St. Paul, 1990, p. 800) put it, an “Institute” is a “principle recognized as authoritative”. We opt for the first, wider, meaning; in this perspective, we can quote Emperor’s Justinian Institutiones, that is, the set of principles applicable within the Roman Empire.


As an authority of PIL observed in this regard: “So the maxim ubi societas ibi jus est correctly puts before us society and law as mutually dependent. They must have been inseparable as facts from the earliest time at which there was any intercourse between men, probably before there was any clear consciousness of the notions corresponding to the facts, and they are still inseparable in all departments of intercourse between men. Without society no law, without law no society. When we assert that there is such a thing as international law, we assert that there is such a thing as international law, we assert that there is a society of states: when we recognise that there is a society of states, we recognise that there is international law”, J. Westlake, Chapters on the Principles of International Law, Cambridge, 1894, at 3. Earlier, one the founding fathers of this province of Law wrote: “This Sociability … or this Care of maintaining Society … is the Fountain of Right, properly so called”, H. Grotius, Prolegomena VIII.


“International law postulates for the existence of certain rules: societas ibi ius”, J. Basdevant, “Règles générales du droit de la paix”, RCADI, vol. 58 1936–IV, p. 513; Heffter, quoted this formula at the commencement of his seminal handbook on International Law (Le droit international public de l’Europe, Paris, 1866, p. 2), thus bridging the gap between legal order and social reality. See, in the same vein: H. Grotius, The Rights of War and Peace (1625), translated from Latin, Prolegomena VIII; M. Giuliano, T. Scovazzi, T. Treves, Diritto internazionale, vol. I, Milan, 1983, p. 186. One of the most influential international jurists (straddling between the end of XIX and the beginning of the XX Centuries) observed: “It is sometimes said that there can be no Law between Nations because they acknowledge no common superior authority, no International Executive capable of enforcing the precepts of International Law. This objection admits various answers: First, it is a matter of fact that States and Nations recognize the existence and independence of each other; and out of a recognized society of Nations, as out of a society of individuals, Law must necessarily spring”, Sir Robert Phillimore, 1879, Vol. I (Part I), § 50 (p. 76).


However, as it has been acutely highlighted: “We have bluntly recognized the dependence of positive international law towards the action of power, and underlined the limits it marks as to its efficiency. This frank recognition of a political fact, imposed quite evidently, is in our opinion the condition to any progress. From an individualist recognition of power between Nations, the fundamental deficiencies of the international order apply. The growing insecurity it generates shakes the legal foundations; it paralyses the workings of international organs; it diverts the minds from the moral disciplines and leads them to the use of violence. The State is no more an environment of security; its impotence in ensuring it forces to look into the redistribution of power in the international organization”, Ch. De Visscher, Théories et réalités en droit international public, 2nd ed., Paris, 1955, pp. 449–450 [our translation].