Colloque - Alex Mills : Private International Law and the Possibility of Extraterrestrial Property: ''Finders, Keepers'' or ''the Province of All Mankind''?

Samantha Besson

Droit international des institutions

Collège de France

Année 2025-2026

The "Province of All Mankind"? Property in Outer Space under Public and Private International Law & Philosophy

Colloque - Alex Mills: Private International Law and the Possibility of Extraterrestrial Property: "Finders, Keepers" or "the Province of All Mankind"?

Private International Law and the Possibility of Extraterrestrial Property: "Finders, Keepers" or "the Province of All Mankind"?

Panel 1: Sovereignty, Jurisdiction and Property in Outer Space

Colloque organisé par la Pr Samantha Besson, chaire Droit international des institutions, les 25 et 26 septembre 2025

Présentation

As it is the case in other (marine or polar) "spaces" of international law usually defined negatively as areas beyond the (territorial) jurisdiction of States, a "non-appropriation" principle applies to the outer space (art. II 1967 Outer Space Treaty; art. 11(2-3) 1979 Moon Agreement). Despite later clarifications in the 1979 Moon Agreement, States still disagree, however, about both the material scope of the principle of non-appropriation (celestial bodies only, or both the bodies and their extracted resources) and its personal scope (public appropriation in the form of sovereign claims by States only, or both public and private appropriation). They also disagree about the implications of the second, more positive principle that was added in the Moon Agreement, i.e. that of "common heritage of mankind" (art. 11(1) Moon Agreement) and about the content of the further principle of "equitable access and sharing of benefits" (art. 11(7d) Moon Agreement) that applies to the common exploitation of celestial resources. In any case, due to the limited number of State ratifications (17 to date), the Moon Agreement is not considered as an expression of universally binding customary law. The same applies to the international regime for the common exploitation of the natural resources of celestial bodies foreseen by the agreement (art. 11(5-7) and 18 Moon Agreement).

This disagreement is sharpened by the tension between those more recent principles, including non-appropriation through use, and the original principles of the international law of "areas beyond national jurisdiction", i.e. the principle of "freedom of exploration and use" (art. I(1) Outer Space Treaty) and its twin principle, i.e. the "freedom of scientific investigation" (art. I(3) Outer Space Treaty; art. 6(1) Moon Agreement). Those original principles have been left untouched by the new ones, indeed, and seem to accommodate free appropriation of resources through use, even if those freedoms have to be "carried out for the benefit and in the interests of all countries" (art. I(1) Outer Space Treaty; art. 4(1) Moon Agreement). The same tensions between the original principles and the subsequent ones also apply within other spaces of international law such as the high seas and deep seabed and have not been resolved by the 2023 Agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas beyond National Jurisdiction.

This indeterminacy has led certain States and regional organizations to adopt domestic (public and private) legislation, develop soft law and/or conclude bilateral agreements to secure the property rights and investments of private companies authorized by those States to explore and exploit celestial bodies and their resources. Their hope thereby is to shape what is called, in international treaty law, a "subsequent practice in the application of treaties establishing an agreement". If those States were to succeed, that practice could influence the interpretation of the Outer Space Treaty. After all, this is exactly what some States did in 1982 after the adoption of the Convention of the Law on the Sea and following their disagreements about the organization of the international regime for the common exploitation of the deep seabed resources in the convention. So-doing, they steered that regime towards the 1994 compromise and the modification of the convention that ensued and, arguably, led to that regime's contemporary deadlock.

This situation raises numerous questions about the kind of international law of outer space the international community of peoples should aim at developing. This is especially the case if we are to prevent the "enclosure" through public and private appropriation of what art. I(1) Outer Space Treaty refers to as the "province of all mankind". It also raises difficult questions about the state of our legal imaginary at a turning point of life on Earth. Are our legal categories themselves at risk of being prematurely "enclosed" by the binary opposition between (State) territory and space, by the opposition between the "common" and the public or the private, and by a given articulation of property to sovereignty?

This two-day conference will bring public and private international lawyers together with political and legal philosophers to discuss the complex issues raised by property in outer space, including its relations to the notions of territory, jurisdiction and sovereignty, but also the international legal status of scientific research, data and samples. The discussions will be organized around three central issues: (i) the relations between property, jurisdiction and sovereignty, and their implications in outer space; (ii) the prospects of "commoning" in outer space, and of a distinct future international institution and regime to govern the common use of celestial resources as currently discussed by the United Nations' Committee on the Peaceful Use of Outer Space (COPUOS); and (iii) the public and common good of science, and its implications for a better distinction between scientific "exploration" and commercial "use", exploitation or appropriation of and by science in outer space.

Participants/Speakers: Philippe Achilleas (University of Paris-Saclay); Michael Byers (University of British Columbia, Vancouver); Isabel Feichtner (University of Würzburg); Stephan Hobe (University of Cologne); Maria Manoli (University of Aberdeen); Michela Massimi (University of Edinburgh); Alex Mills (University College, London); Margaret Moore (Queen's University, Ontario); Yannick Radi (Catholic University of Louvain); Lukas Rass-Masson (University of Toulouse Capitole); Anna Stilz (University of Berkeley); Fabio Tronchetti (University of Northumbria); Jonathan B. Wiener (Duke University); Katrina M. Wyman (New York University).