Orbital Denial and the Limits of the Outer Space Treaty: The Contested Legal Status of Kinetic and Conventional Space Systems

The Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space (1967) is the constitutional instrument of the space domain, but its central security provision, Article IV, is an artefact of a particular Cold-War bargain. It prohibits the placement of nuclear weapons and other weapons of mass destruction in orbit and reserves the Moon and other celestial bodies for "exclusively peaceful purposes," while saying nothing whatever about conventional, kinetic, or dual-use systems in Earth orbit. That silence is not a gap the Treaty forgot to fill; it is the space the negotiators deliberately left open, and it has since widened into a large and consequential grey zone. This paper argues that "orbital denial" — the capacity to deny an adversary the use of an orbital region or of a specific space capability — is for that reason legally contested rather than clearly prohibited, and that the contest cannot be resolved by the instrument scholars instinctively reach for, a new multilateral treaty. It proceeds in five movements: an interpretive analysis of Article IV's text, structure, and travaux, and of the enduring "non-aggressive versus non-military" dispute over "peaceful purposes"; a mapping of where kinetic, conventional, and anti-satellite (ASAT) systems fall as a matter of law, and of why the residual-freedom baseline inherited from Lotus makes their status contested; an account of the ancillary regime — the Liability Convention, the Registration Convention, and the debris/Kessler-syndrome and environmental-law dimension of Article IX — and its inadequacy to the problem; a survey of the contemporary policy landscape, from the deadlocked PAROS process and the Russia–China PPWT to the 2022–2026 turn toward "responsible behaviours" in the UN Open-Ended Working Groups and the Group of Governmental Experts, the 2022 United States moratorium on destructive direct-ascent ASAT testing and the state practice that followed it, and the militarisation-versus-weaponisation distinction that organises the whole field. It closes with a normative proposal in the author's own voice, extending his prior work on the "Magnitsky model": that the Treaty's conventional-systems gap is best filled not by a convention that will not be concluded, but by targeted, nationally-anchored measures — built on, rather than circumventing, the authorisation-and-supervision duty that Article VI already imposes, with each market-access consequence resting on its own domestic legal basis — which harden the emergent responsible-behaviour norms by attaching domestic consequences to irresponsible orbital-denial conduct and letting those consequences cascade through the commercial space economy. The proposal is offered as the author's original contribution and as a model for legislative adaptation, not as a statement of existing law. Preprint; not yet peer reviewed.