In Conversation with Judge Leonardo Nemer Caldeira Brant

Judge Brant, thank you very much for accepting this invitation from the Völkerrechtsblog, which will constitute part of a Völkerrechtsblog series: The Person behind the Practitioner.

I am grateful to the Völkerrechtsblog and to you, Antonio, for giving me the opportunity to share my insights and experience in international law.

To frame this short interview, it would be to the benefit of our readers to try to synthesize some of your extensive international law career. Leonardo Nemer Caldeira Brant has been a member of the International Court of Justice since November 2022. Before his appointment to the Court, he earned a PhD in International Law with a thesis titled “The Authority of Res Judicata in International Law” at the Université Paris-Ouest Nanterre-La Défense, for which he was awarded the “Prix du Ministère de la Recherche, Département Sciences de la Société de la République Française”. He was a tenured Professor of International Law at the Federal University of Minas Gerais in Brazil. With over two decades of experience as a practicing lawyer and a prolific scholar, he has held visiting professorships at the Institut d’Études Politiques d’Aix-en-Provence; Université Paris-Ouest Nanterre-La Défense; Institut des Hautes Études Internationales; Université Panthéon-Assas; Université de Caen Basse-Normandie, France; and the University of Cambridge, United Kingdom. He served as a legal officer at the Registry’s Department of Legal Matters of the International Court of Justice and has also worked as a lawyer at the International Affairs for the Municipality of Belo Horizonte. He was a member of the list of judges for the composition of the Special Tribunal for Lebanon and a member of the Committee for Nominations of the International Criminal Court. Finally, he is the founder of the Center for International Law  (CEDIN) and the founder and editor in chief of the Brazilian Yearbook of International Law.

Judge Brant, I find it hard not to begin this interview by asking you about your time as a Legal Officer for the Court. Almost two decades later, you would be coming back to the Peace Palace as a Judge. How was your time at the Court back then compared to now? And did you ever consider the possibility of returning as a Judge?

It goes without saying that this experience was very enriching and allowed me to deepen my knowledge of international law. Thanks to it, I wrote a book on the Court’s case law, which I published in Portuguese. This compendium of the Court’s case law up to 2003 was the first publication of its kind in Portuguese, specifically aimed at Brazilian students. On another point, I am proud to have been one of the first Brazilians to occupy this position.

The prospect of becoming a judge is so exceptional that I don’t think I ever considered it in those terms at the time. That said, I wrote my PhD on the Court’s authority of res judicata, and I have always kept the Court in mind in both my teaching and academic work. While I haven’t oriented my career towards this objective, I am convinced that my professional background and several of my experiences have equipped me with the skills and expertise necessary to assume my current responsibilities.

During your recent keynote speech on the occasion of the Launching of the Latin American and Caribbean Journal of International Law, you named some of the doctrines, principles and customs that have originated in the practice of Latin American States or that have been proposed by Latin American Jurists. To name a few, the utis posidetis iuris, on matters related to boundaries; the Drago Doctrine on the prohibition of military intervention based on national credit default and the principle of non-intervention.

To know about the rules, and the applicable law to a particular issue appears critical for lawyers, students, and, of course, Judges, but their backgrounds and origins are normally not as well known or well-studied. Out of curiosity, I would like to ask you to what extent is this historical background important for the application of so many and so different rules of international law.

The question you are asking is particularly close to my heart, and I am grateful to you for raising it.

Allow me, however, to make a remark: I do not believe that one can say that these Latin American doctrines are “normally not as well known or well-studied”. Indeed, the origins of Latin American doctrines are better known than they appear, and the origin of some of them can be easily understood when they bear the very name of their conceiver. Consider, for example, the Drago Doctrine! Moreover, I am every day delighted to see in the hallways of the Peace Palace the statues of illustrious Latin American lawyers.

I believe that behind your question lies a more complex phenomenon, as none of us relies on a single “background.” I myself have several backgrounds: as a Brazilian, I sometimes cannot help but see similarities between our constitutional law and certain aspects of international law; as a Latin American, of course, I share the commitment to human rights, the preservation of the independence of States, and their sovereignty (principles which are enshrined in Article 4 of the Brazilian Constitution); and as a jurist trained in the Romano-Germanic tradition, I am naturally attached to the respect for procedural principles which are foreseen in the Statute and the Rules of the Court.

Here is the strength of the International Court of Justice: that each of its 15 members comes with all their different backgrounds. Therein lies its universal character, in the truest sense of the term.

A question that has figured in this series and that is of great interest to many young international lawyers has to do with legal skills. You have acted in many capacities as an international lawyer. Likewise, you now see very many practitioners, from the public and the private spheres act and intervene before the Court. Would you like to share with us what in your opinion are some of the most important skills for an international lawyer to develop?

This is a question that comes up often, especially among younger colleagues entering the field, and I think it’s an important one.

Naturally, when we speak about the skills required to be an international lawyer, the first things that come to mind are the obvious: language proficiency, strong academic training, solid legal reasoning, and practical experience. And of course, all of that is essential. But in many ways, those are the fundamentals—they’re the starting point, not necessarily what distinguishes one practitioner from another.

What I believe truly makes a difference are more personal qualities. And if I had to highlight three, they would be the following:

First, be decent.

It may sound basic, but decency is incredibly important. Treating others with respect, maintaining honesty, and acting with humility—these are not just ethical values, they are professional strengths.

Second, be faithful to your beliefs.

In the field of international law, one is often required to navigate highly complex and sensitive situations. Without a clear sense of one’s values and convictions, it becomes easy to lose direction. It is your principles that ultimately anchor you in your work.

And third, be resilient.

If you truly believe in the work you are doing, and you stay consistent, you will arrive somewhere. It may not always be the Court, or the place you first imagined, but it will likely be somewhere meaningful and fulfilling.

So, while the technical skills are important, I think in the long term, it is these personal qualities—decency, integrity, and resilience—that define not just a capable international lawyer, but one who can truly make a difference.

Those who are lucky will normally have found a guide or mentor in their careers. It is indeed not rare to know about great international lawyers who began as mentees of other prominent scholars or practitioners. But this is of course not always the case. I was wondering if you could please share with us if you ever had such guidance and support when you were a student in Brazil or France and how important was this for your development as a lawyer.

Thank you for the question. If I may, I’d like to begin by slightly rephrasing it. I don’t believe it’s really a matter of luck. Being guided by someone you respect and admire is not something that simply happens to you. It’s something you need to earn. You have to show, at every opportunity, that you possess the qualities that might deserve that person’s attention and time.

In that sense, I believe we should always remain grateful to those around us—because learning and growth do not come only from a single, ideal mentor. It’s not about waiting for the “ideal guide” who will give you all the answers or show you the one right path. The real question is: how do we learn—not just from a mentor, but from everyone around us?

It’s the ability to learn that changes how we see others. And from that perspective, even those who might have caused you harm, or challenged you, can also teach you something important.

I would also say that the term “guide” might not be the most accurate. Because true guidance doesn’t come from someone giving you ready-made answers. A real mentor—or let’s say, an inspiration—is someone whose vision, career, or way of thinking helps you ask better questions and build your own answers. Their role is not to replace your judgment, but to enrich it.

And sometimes, that process means disagreeing with them. In fact, I believe disagreement is often more valuable than passive acceptance. The moment you’re able to say “I disagree” to someone you admire—that’s when you know they’ve really inspired you.

In my own life, I’ve been fortunate to have had many friends and colleagues from whom I’ve learned a lot, and who have deeply inspired and supported me in my professional journey. Among them, I’d mention Professor Báracho, Professor Arthur Diniz, Judge Rezek, and Professor Alain Pellet. Each of them, in their own way, helped shape my thinking and supported me at key moments in my development as a lawyer.

My final question is perhaps related to the previous one. In academia, it is not uncommon to find guidance and inspiration in the work of other scholars. For instance, this is of great value for defining writing structure. In your experience as a judge, do you draw inspiration or guidance from the structure or style of a particular judicial decision or is it always a case-by-case approach?

As judges (and, more fundamentally, as individuals) our decisions inevitably reflect the choices we make based on our experiences. Of course, certain experiences leave a stronger mark and carry more weight than others. But I believe the key lies in finding the right balance between personal convictions and professional responsibility.

Let me give an example. As a professor, you enjoy a certain freedom. You are free to express your opinions, to say what should be the law in your view. And that freedom of thought and expression is one of the great advantages of academic life.

But as a judge, your role is different. You are not there to say what the law ought to be but what the law is. And in doing so, you operate within a framework of procedural and institutional constraints that limit the extent to which your personal views can be expressed.

So, in academia, it is natural to find inspiration and guidance in the work of other scholars. Their ideas can help shape how we structure our arguments, how we frame issues, how we propose developments in the law.

As a judge, however, the sources of inspiration are often different. You are more likely to find guidance in the jurisprudence of the Court itself, in its previous decisions. That doesn’t mean, of course, that an academic background becomes irrelevant. In fact, it can be a great asset. It helps you think more critically, see the broader context, and contribute (within the boundaries of your role) to the progressive development of international law. But again, always with that balance between your intellectual background and the duties imposed by your judicial function.

Judge Brant, thank you very much for taking the time for this interview and for sharing what will be a very interesting read for many readers. I am confident that these insights and your advice for young lawyers and scholars will be greatly appreciated. It has been a pleasure to have you at the Völkerrechtsblog.

Thank you, it has been a pleasure!