The use of outer space for military purposes continues to be a central use of outer space, not only because of the dual-use nature of most space technology, but especially considering the recent challenges arising from the war in Ukraine. For instance, in November 2022, Russia launched a rocket carrying a military satellite and, in July 2022, the Atlas 5 rocket launched two US military satellites to test a technology aimed at detecting and tracking enemy hypersonic missiles. Also in 2022, France conducted its second outer space military exercise, codenamed “AsterX”. Guidance for military uses of outer space has thus recently emerged as a legal priority, notably through two recent initiatives: the McGill Manual on International Law Applicable to Armed Conflict in Space (MILAMOS) and the Woomera Manual on the International Law of Military Space Activities and Operations.

Military uses of outer space are not prohibited. However, aggressive uses have been considered forbidden under international rules, not only to prevent threats to the physical and operational integrity of human-made objects in space, but also to protect Earth from threats originating in space, either kinetic, non-kinetic or hybrid.

In this respect, at the international level, the UN Open-ended Working Group (OEWG) on Reducing Space Threats was set up on 30 December 2021 to make recommendations on possible norms, rules and principles of responsible behaviours relating to threats by States to space systems, including, as appropriate, how they would contribute to the negotiation of legally binding instruments, such as on the prevention of an arms race in outer space. UNGA Resolution 75/36 encouraged Member States to study existing and potential threats and security risks to space systems. The OEWG is integrated in the UN mandate on the prevention of an arms race in outer space (PAROS), with the Conference on Disarmament (CD) being the multilateral disarmament negotiating forum focusing, among other topics, on PAROS.

Several Resolutions have been recently issued in this scope, including Resolution 76/22 on the prevention of an arms race in outer space, Resolution 76/230 on further practical measures for the prevention of an arms race in outer space, Resolution 76/23 on no first placement of weapons in outer space, and Resolution 76/55 on transparency and confidence-building measures (TCBMs) in outer space activities (with further draft Resolutions having been discussed in the last UNGA session). The need for an international legally binding instrument to establish reliable guarantees against an arms race in outer space has also been pointed out several times, including under COPUOS (UN Committee on the Peaceful Uses of Outer Space). In this respect, COPUOS Scientific and Technical subcommittee's final Report of its February session expressly notes that it is States’ responsibility to ensure that the use of nuclear power sources in outer space is strictly for peaceful purposes, avoiding at all costs the placement in Earth orbit, celestial bodies or outer space in general of any object carrying nuclear weapons or any other type of weapon of mass destruction.

Military uses of outer space / disarmament of outer space has also been addressed by States before the UN, such as by the US and EU. Note also that the BRICS countries issued a Joint Statement reasserting their pledge to “ensuring the long-term sustainability of outer space activities and prevention of an arms race in outer space (PAROS) and of its weaponization, including through negotiations to adopt a relevant legally binding multilateral instrument”.

Additionally, the highly complex challenges of international law in the context of outer space have been stressed, among others, by the International Committee of the Red Cross May 2022 Working Paper on constraints under international law on military operations in, or in relation to, outer space during armed conflicts.

Concerns relating to space threats and the disarmament of outer space were sparked by recent anti-satellite tests (ASAT), which led to fears about attempts to weaponize space. Indeed, in the last couple of years, there has been a resurgence of ASAT Tests. For instance, in November 2021, Russia conducted an anti-satellite test striking the satellite Cosmos 1408 and creating a cloud of more than 1,500 pieces of orbital debris. Since then, the International Space Station has had to perform two different evasive manoeuvres (in June 2022 and October 2022) in order to avoid collision with  the debris. As a result, several initiatives addressing anti-satellite tests have been put forward. Although there is no international legal instrument specifically aimed at regulating the threats and risks of ASAT, at the first session of the OEWG on Reducing Space Threats, which took place in May 2022, several countries supported a commitment not to conduct destructive anti-satellite tests, with the second session having already taken place in September 2022. The UN First Committee has also approved a Resolution to ban ASAT. In addition, the US had already adopted, in April 2022, a specific Moratorium on the destructive testing of direct-ascent anti-satellite (DA-ASAT) missile systems, in which it pledged to voluntarily refrain from and “not conduct destructive, direct-ascent anti-satellite (ASAT) missile testing”. Other countries have joined this ASAT testing ban. Moreover, following the signature of a Memorandum of Understanding concerning Enhanced Space Cooperation (April 2022), the UK and the US have been strengthening their partnership on space-related security matters, especially in light of concerns that satellites are becoming military targets and the need for a stronger defence posture in space security.

At the same time, several nations (especially the US, Russia and China) have been conducting demonstrations and tests of Rendezvous Proximity Operations (RPO) both in LEO and GEO. Although RPO can be used for purposes such as in-orbit servicing, debris removal and other civil or commercial peaceful uses, RPO can also be used for hostile and counter-space purposes, as highlighted, for instance, by the EU. Indeed, as conveyed by the Secure World Foundation’s 2022 Global Counterspace Capabilities Report, it is extremely difficult to determine intent in such operations. As an example of a RPO with commercial / peaceful purposes, Astroscale’s ELSA-d Mission successfully completed a RPO for end-of-life in-orbit services which avoided collision with other satellites and safeguarded the orbital environment, having been the first private commercial mission on RPO. 

Threats of disruptions of satellites is another hot topic at the moment, following Russia’s threats to commercial satellites – Starlink satellites – within the context of the Ukraine war. The risk of such an attack being considered legitimate or a use of force / armed attack under the Charter of the United Nations and international humanitarian law, even if performed through cyber means, raises not only the prospect of an escalation, but also of debris affecting the sustainable use of outer space. The legal issues arising therefrom are quite complex and have not yet been tested.

In addition, security on Earth from natural hazards originating in space (including NEOs and space weather) continues to be a relevant topic. For instance, NASA’s DART Mission hit an asteroid, in September 2022, in the first-ever probe to rendezvous with a binary asteroid system, thus demonstrating the current capabilities for asteroid deflection through kinetic means, as well as the role of RPO in planetary defence. ESA’s Hera Mission will, as a next step, return to the asteroid to investigate the consequences of the impact.