Discussions of international law often focus on questions of constraint and prohibition. This year's Annual Meeting considered the role of international law as an instrument. Actors on the international stage use a variety of tools to address their concerns, from climate change to economic development; from humanitarian crises to cross-border disputes; from commercial regulation to global trade. Governments and international organizations employ diplomacy and coercion, corporations use negotiation and persuasion, and non-governmental organizations engage in fact-finding and advocacy. And all of these actors affect and are affected by international law and use the international legal system to effectuate change and solve problems.

The 2019 Annual Meeting of the American Society of International Law (ASIL)—attended by more than 1,250 persons—focused on the distinctive ways international law serves as an instrument that national and international actors invoke and deploy, and by which they are constrained. It opened with Martti Koskenniemi, Academy Professor and Director of the Erik Castrén Institute of International Law and Human Rights at the University of Helsinki, delivering the twenty-first annual Grotius Lecture on the topic, Enchanted by the Tools? International Law and Enlightenment. Anne Orford of the University of Melbourne School of Law provided the response. At the Society's Fourth Annual Assembly, memorial tributes were made to Ambassador Richard N. Gardner by Past President Lori Damrosch, to Prosper Weil by Honorary President Michael Reisman, and to Judge Patricia M. Wald by Jenny Martinez, Professor of Law and Dean of Stanford Law School. The Assembly address was delivered by Mónica Pinto of the University of Buenos Aires Faculty of Law, on the theme International Law as an Instrument: Dialogues, Tensions, Accomplishments. Also at the Annual Meeting, the Society presented the Manley O. Hudson Medal to Associate Justice Stephen Breyer of the U.S. Supreme Court and the Goler T. Butcher Medal to Zeid Ra'ad Al Hussein, the former UN High Commissioner for Human Rights. Tracy Robinson of the University of West Indies Faculty of Law received the 2019 Prominent Woman in International Law Award. The Annual Assembly included a keynote address, A Tribute to Robert H. Jackson, by Judge Chile Eboe-Osuji, President of the International Criminal Court, and the Seventh Annual Charles N. Brower Lecture in International Dispute Resolution, delivered by Judge Peter Tomka of the International Court of Justice on A Century of Dispute Settlement through International Law, 1919–2019: The Role of Multilateralism. A closing plenary was held on International Law as an Instrument for Development.

The Meeting's more than forty substantive panels considered “International Law as an Instrument” across areas within international law—from space to the deep seabed—as well as late-breaking panels on Brexit and the crisis in Venezuela. The 218 speakers came from all over the world, from private practice, corporations, government, international institutions, and non-governmental organizations, and included the highest percentage of people of color (25 percent) at an Annual Meeting. We are particularly grateful to the members of the Annual Meeting Committee, themselves a reflection of the diversity and scope of the profession, who contributed their expertise and time to developing and perfecting these panels, and to ASIL's staff, who worked tirelessly to make what is an exceedingly complex operation such a success.

We hope that the Annual Meeting provided a greater understanding of the complex operation of international law, and the reality of its role as a tool for actors on the global stage, and not just as a constraint. We are grateful to the contributors to these Proceedings for creating a permanent record of the discussions that took place.