Professor Emeritus of Public International Law Pieter Hendrik (Peter) Kooijmans passed away on 13 February 2013. He leaves a lasting void within the international-law community both inside and outside the Netherlands.

Throughout his life, Peter Kooijmans served with great authority and unwavering commitment the development of the ‘law of nations’ – to use his preferred term – through his scholarship, his teaching, and his responsibilities within the practice of international law. Peter wrote his doctoral dissertation with Professor Gesina van der Molen at the Free University in Amsterdam. It was published in 1964 with the title ‘The Doctrine of the Legal Equality of States: An Inquiry into the Foundations of International Law’ and it remains a standard work on the topic to this day.Footnote ¹ At this same university, Kooijmans was a Professor of European and Public International law from 1965 until 1973. In the latter year, he started a four-year term as State Secretary (Staatssecretaris) for Foreign Affairs of the Netherlands.

In 1978, Professor Kooijmans returned to academia and joined the Leiden University Faculty of Law. The subjects of his respective inaugural lectures – ‘The Law of Nations and Social Justice’ (1965) and ‘Law of Nations Studies and the Crisis of the Law of Nations’ (1978)Footnote ² – reflect how his view on the advancement of the international legal order was on the one hand rooted in a solid analysis of the existing law and on the other hand guided by a firm conviction about the law's dual function: that is, to secure order and stability within international society and to promote justice and human dignity worldwide. Throughout his career, Kooijmans was a dedicated protagonist of human rights.Footnote ³ Between 1985 and 1992 he was the first UN Special Rapporteur on Questions Relevant to Torture. He drew from this experience in dealing with international law within the United Nations and the political context at large, when teaching generations of Leiden students. Peter Kooijmans taught with such authority, clarity, and inspiration that many consider his lectures to be among the highlights of their legal studies. Peter was an active and much-loved professor.Footnote ⁴ He was one of the founding editors of the Leiden Journal of International Law, an enthusiastic supporter of the Telders International Law Moot Court Competition, and – for his wit and amiability – a welcome guest at academic events in general. Those who had the privilege of working with Peter Kooijmans as their Doktorvater experienced his sharp legal analyses typically coupled with concern for questions of justice and legitimacy in that context. Wise and well-considered, in line with the true ideals of academia, Peter supervised doctoral research by way of questioning, leaving one free to discover one's own questions, method, and arguments, in order to seek to become the independent and mature scholar one wanted to be. Peter was there and enjoyed the process.

After he left Leiden, first for a year and a half to serve the Dutch government as Minister for Foreign Affairs (1993–94)Footnote ⁵ and then for good in 1997, he was called to the bench of the World Court; he was thus accorded emeritus status and the Leiden academic community lost one of its eminent leaders. The international community, however, was enriched with a wise and active judge.Footnote ⁶ In his nine years at the ICJ, Judge Kooijmans wrote one Dissenting Opinion, two (joint) Declarations, and 12 (joint) Separate Opinions, of which the joint Separate Opinion with Judges Higgins and Buergenthal in the Arrest Warrant case seems to be most noted; one may suspect, moreover, an active role in the drafting of many decisions.

Until the very end, whether in private conversations or in a newspaper op-ed, Peter Kooijmans remained faithful to his vision of international law. It is genuine law, which exists independently of politics. It is the legal framework within which interests are to be weighed and judged. When things get difficult, that legal framework should not be discarded but developed further with intellectual and political courage. That same courage Peter himself demonstrated throughout his life, whether in his work as a scholar, human rights rapporteur, minister for foreign affairs, or ICJ judge, always working from the conviction that the international community is ultimately a community of ‘the entire human race’,Footnote ⁷ a societas humana, served best by a strengthening of respect for the international rule of law. In this vision, Peter had been influenced by his doctoral supervisor, Gesina van der Molen, and inspired by Leiden giants who had preceded him, Cornélis van Vollenhoven and Hugo de Groot. He kept returning to the latter throughout his life. Not so much because Grotius would provide answers to contemporary challenges, but because Peter admired Grotius's professional attitude and his persistence in striving to bring sovereign states under the rule of law. Peter Kooijmans himself maintained this attitude when he was faced with the tension between the law-as-it-is and the law-as-it-should-be, and would give full weight to arguments and values such as human rights while upholding the law's function to secure order and peace.

In 2007, upon recommendation of the government, Her Majesty the Queen bestowed Kooijmans with the exceptional, honorary title of Minister of State.

In Peter Kooijmans we lose an outstanding and internationally recognized international-law expert, a highly esteemed colleague, a truly pro-Europe statesman, an inspiring mentor, an exceptional teacher, and a great and loving friend. We shall miss Peter; he will not be forgotten.