by Boudour Mefteh (Policy Intern at CELI)
Outer space has been framed as humanity’s new frontier, one that was meant to be kept for peaceful exploration. In the 1950s, as superpower rivalries heated up on Earth, states recognized that space could not simply be treated like another territory subject to conquest. Even before Sputnik flew (October 1957), the UN called for space to be used for the “betterment of mankind” and to avoid extending terrestrial conflicts into orbit.[1] Early UN resolutions stressed “the common interest of mankind as a whole in furthering the peaceful use of outer space” and the “urgent need to strengthen international co-operation” in this realm.[2] These sentiments paved the way for formal space law: by 1967 the Outer Space Treaty (OST) had codified that all space activities be carried out “for peaceful purposes” and in accordance with international law.[3]
Yet even from the start, space was viewed through a Cold War lens. Both the United States and the USSR sought to ensure that no one side could dominate this new domain. The 1967 OST, negotiated at the height of the nuclear arms race, declared that no nation could claim sovereignty over space or the Moon,[4] and it explicitly bans placing nuclear or other weapons of mass destruction in orbit or on celestial bodies.[5] The Treaty reaffirms that “the exploration and use of outer space, including the Moon and other celestial bodies, shall be carried out for the benefit and in the interests of all countries”.[6] In practice, OST Article IV forbids Weapons of Mass Destruction (WMDs) in space and requires that the Moon and other planets be used “exclusively for peaceful purposes”.[7] It even bans military bases or weapons tests on those celestial bodies. As President Lyndon Johnson remarked at the time, the OST was “the most important arms control development since the limited test ban treaty of 1963.”
Crucially, however, the Outer Space Treaty does not forbid all military uses of space. It prohibits only nuclear and mass-destructive weapons, and only “on the Moon and other celestial bodies,” not in free orbit.[8] Nothing in the OST explicitly bans conventional weapons or routine military activity in the void between planets. Indeed, the United States has long interpreted “peaceful purposes” to mean “non-aggressive” use, rather than “non-military” use. In other words, pure reconnaissance (known as spaying), communications, navigation and other military support activities in space are generally viewed as allowed, so long as no combat is directly waged among satellites. This interpretation has become widely accepted: Bin Cheng for example stating that: “there is no provision, contrary to a very prevalent misconception, anywhere in the Treaty which reserves the whole of outer space exclusively for peaceful use”.[9] Only the Moon and other planets were “demilitarized” by Article IV. Thus, in practice, the OST leaves a large gap: it prevents nuclear arms races in orbit but does not expressly ban all military activities in space, nor the establishment of military space forces or the placement of conventional weapons.[10]
1. International law applies in space as elsewhere
From the outset, the U.N. affirmed that the same legal principles governing Earthly states would apply above. In 1961 the U.N. General Assembly resolved that “international law, including the Charter of the United Nations, applies to outer space and celestial bodies”.[11] The Outer Space Treaty itself echoes this: it requires that all space activities be conducted “in accordance with international law, including the Charter of the United Nations”.[12] Article I of the OST guarantees that outer space is “free for exploration and use by all States … in accordance with international law”,[13] and Article III reiterates that every space actor must respect the U.N. Charter.[14] The Treaty goes further: Article VI makes each state “internationally responsible” for any space activities carried out by its government or evenby private entities under its jurisdiction. In short, there is no “lawless” void: the moment humanity “entered outer space, the overarching regime of international law which governs the rights and responsibilities of States became automatically applicable there”.[15]
By extension, the laws of armed conflict (jus in bello), and the U.N. rules on the use of force (jus ad bellum), are assumed to apply to space warfare as well, just as they govern land, sea and air conflict. The International Court of Justice itself has noted that the laws of war “apply to all forms of warfare and to all kinds of weapons … of the future”.[16] In practice, this means that the U.N. Charter’s ban on aggression, the Geneva Conventions and Hague laws on conduct in war, and even arms-control treaties (like the NPT or biological weapons bans) would all apply in a conflict involving space assets.
Nevertheless, the legal framework is incomplete and fragmented. Unlike the centuries of naval law or decades of air warfare law, space warfare has only a few binding rules.[17] The Outer Space Treaty and its contemporaries (such as the 1963 Partial Test Ban Treaty, which banned nuclear tests in space) were designed in an era when neither side envisioned large-scale space combat. Since then, technology has overtaken lawmaking, and satellites have become indispensable for modern militaries; they provide precision navigation and timing, global communications, missile warning, weather forecasting, reconnaissance and intelligence.[18] In the 1991 Gulf War, for example, U.S. forces relied heavily on GPS and satellite imagery (which led some observers to dub it the “first space war”). Today, those same satellites keep national economies and civilian infrastructure running.
2. Space as a Multi-Domain Warfare
Reflecting this strategic importance, the past few years have seen a military build-up in space. NATO formally declared space its newest domain in 2019,[19] and major powers have created dedicated space forces (the U.S. Space Force in 2019-2020 was the first new U.S. service branch in decades). Russia and China have tested a range of anti-satellite (ASAT) weapons, from direct ascent missiles to so-called “killer satellites” that can rendezvous with and threaten other satellites. These tests show that in a future war, destroying an enemy’s satellites by kinetic means is technically feasible. Indeed, in the 2022 Russian invasion of Ukraine, Russia is alleged to have cyber-attacked the American firm ViaSat’s satellite network just before the ground assault; in effect, jamming Ukrainian comms via space.[20] This incident has led analysts to call the Ukraine conflict the “first space-cyber war,” since it was the first major combat where a space-enabled service was targeted (via cyber means) as part of the campaign.[21] Notably, no one fired a missile into orbit; the attack came through network hacking. That suggests that in an actual space war, cyber-operations against satellites (and ground stations) may well be more common than outright rocket or kinetic strikes on orbiting hardware.
The multi-domain character of space conflict complicates legal analysis. A satellite kill by a missile involves actions in five domains at once: it is launched from land or sea, it flies through airspace, it strikes in outer space, and it has terrestrial economic and possibly collateral effects; even cyberspace effects if the satellite is part of the internet. Each of those domains has its own rules on sovereignty and the use of force (for example, national airspace is sovereign, outer space is not). There is no single “space warfare law.” Instead, the applicable law is drawn from existing sources: the U.N. Charter, the law of armed conflict, the treaty regime on space, and even telecommunications law (since satellites use frequencies). All these rules must be interpreted in concert, and often they leave gray areas.
Examples: If State A launches an ASAT missile from its territory to destroy State B’s satellite, A is using force across airspace and space. The U.N. Charter would require A to justify that as self-defense or Security Council authorization. The Hague and Geneva laws would apply to the conduct (e.g. distinguishing civilian vs military satellites, limiting collateral damage). Simultaneously, the act of firing the missile implicates missile-control regimes: for instance, the Missile Technology Control Regime (MTCR), though nonbinding, restricts the sale of rockets capable of carrying nuclear warheads (and by extension covers many ASAT launch vehicles). If the missile is air-launched, even more rules (air warfare law) could apply. Thus, a single act of space warfare can trigger land, air, sea, space and cyberspace law at once, creating a “regime complex” with overlapping authorities.[22]
3. The role of non-binding instruments
With so few binding rules specific to space, states and scholars have turned to non-binding instruments and dialogue to fill gaps. The U.N. Committee on the Peaceful Uses of Outer Space (COPUOS) and the Conference on Disarmament have long discussed preventing an arms race in space (PAROS), but have only produced resolutions and draft treaties that never entered force. For example, Russia and China in 2008/2014 proposed a legally binding treaty to ban all weapons in space (the PPWT), but it failed to gain consensus. The EU’s 2008 proposal for an International Code of Conduct on Outer Space (covering both civilian and military activities) also did not advance beyond negotiations. In practice, the U.N. approach has been to craft voluntary transparency and confidence-building measures (TCBMs) and norms. A 2013 Group of Governmental Experts (GGE) produced non-binding recommendations on information-sharing and “no first placement” of weapons. More recently, the U.N. General Assembly has urged states to develop “norms, rules and principles of responsible behaviours” in spacedisarmament.unoda.org. In December 2020, the U.N. endorsed the idea of negotiating such norms, calling for states and NGOs to submit ideas. By early 2021, multiple spacefaring nations (including the U.S, U.K., France, Germany and Australia) issued a joint vision, stressing that “space is integral to modern multi-domain military operations and provides [a] strategic advantage” [23], language mirroring one of the principles in the U.S.-led 2031 Space Operations vision. Those principles emphasize responsible military behavior in space, mutual assistance, and preventing conflict from extending into orbit.
But none of these pledges is legally binding; They depend on political will. The jurisprudence of space war is almost nonexistent. In contrast, on land and sea, hundreds of years of practice, treaties and even case law (ICJ rulings, etc.) have created widely accepted wartime norms. If a future great-power conflict were to spread into space, it is unclear what rules states would actually follow. Will they pretend the silent norms of the 1967 Treaty still hold sway? Will they at least attempt to honor the new confidence-building measures and norms of behavior? Or might they fight “lawlessly,” exploiting every technical capability, kinetic ASAT, co-orbital weapons, cyberattack on satellites, without restraint?
Conclusion
Today, the legal regime for space conflict is best viewed as polycentric. Core international law (U.N. Charter, law of armed conflict, OST Article III) applies generally, but specialized space law remains sparse. Key treaties (OST, Partial Test Ban, environmental modification conventions) prohibit only certain weapons or environmental warfare. Beyond these, a web of UN forums (General Assembly, Security Council, ICJ) and specialized bodies (COPUOS, Conference on Disarmament, Open-ended Working Groups) provide venues to debate and issue statements. Independent initiatives – such as the McGill “MILAMOS” manual project and similar expert efforts – try to clarify how existing law (from other domains) should apply in space.
In sum, the idea of space as a “warfighting domain” has gone from science fiction to policy fact. The hope that space remains forever “the province of all mankind” for peaceful use still underpins our laws and treaties,[24] but reality is forcing hard questions. Can a sustainable order in space be built without new treaties, or will future wars force creative interpretations of old rules? Will the promise of peaceful space prevail, or will Earth’s conflicts be fully transposed into the final frontier?
[1] U.S. Department of State, Foreign Relations of the United States, 1958–1960, United Nations and General International Matters, Volume II, Document 460, “Position Paper Prepared for the Fourteenth Regular Session of the United Nations General Assembly (Program for International Cooperation in the Field of Outer Space),” Washington, September 9, 1959, SD/A C.1/491, Office of the Historian, History.State.Gov, https://history.state.gov/historicaldocuments/frus1958-60v02/d460
[2] United Nations General Assembly, Resolution 1721 (XVI), International Co-operation in the Peaceful Uses of Outer Space, adopted 20 December 1961, UN Doc. A/RES/1721(XVI), United Nations Office for Outer Space Affairs, https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/resolutions/res_16_1721.html
[3] Articles III, IV. United Nations, Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (Outer Space Treaty), adopted by UNGA Res. 2222 (XXI) 19 December 1966, opened for signature 27 January 1967, entered into force 10 October 1967, United Nations Office for Outer Space Affairs, https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/outerspacetreaty.html
[4] Article II, Ibid.
[5] Articles III, IV, Ibid.
[6] Article I, Ibid.
[7] Article IV, Ibid.
[8] Ibid.
[9] Bin Cheng, “Properly Speaking, Only Celestial Bodies Have Been Reserved for Use Exclusively for Peaceful (Non-Military) Purposes, but Not Outer Void Space”, Int’l L. Stud. Vol. 75 (U.S. Nav. War Coll.), https://digital-commons.usnwc.edu/cgi/viewcontent.cgi?article=1434&context=ils&utm
[10] Babak Shakouri Hassanabadi, “Space Force and International Space Law,” The Space Review, July 30, 2018, https://www.thespacereview.com/article/3543/1
[11] United Nations General Assembly, Resolution 1721 (XVI), International Co‑operation in the Peaceful Uses of Outer Space, 1085th plenary meeting, 20 December 1961, UN Doc. A/RES/1721(XVI), United Nations Office for Outer Space Affairs, https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/resolutions/res_16_1721.html
[12] OST Article III, Ibid.
[13] Ibid.
[14] Ibid.
[15] Ram S. Jakhu, Cassandra Steer and Chen Kuan-Wei, ‘Conflicts in Space and the Rule of Law’ (2017) 66 ZLW (German Journal of Air and Space Law) 657, 663.
[16] International Court of Justice, Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, ICJ Reports 1996, 226, July 8, 1996, I.C.J. Reports 1996, pp. 226 et seq. In paragraph 86 https://law.justia.com/cases/foreign/international/1996-icj-rep-66.html
[17] NATO, “NATO’s Approach to Space,” updated July 30, 2025, NATO, https://www.nato.int/en/what-we-do/deterrence-and-defence/natos-approach-to-space
[18] U.S. Department of Defense et al., Combined Space Operations Vision 2031, February 22, 2022, https://media.defense.gov/2022/Feb/22/2002942592/-1/-1/1/CSPO%20VISION%202031_220222.PDF
[19] NATO, “NATO’s Approach to Space,” Ibid.
[20] Eytan Tepper, The First Space‑Cyber War and the Need for New Regimes and Policies, Policy Brief No. 173, Centre for International Governance Innovation (CIGI), May 2022, https://www.cigionline.org/static/documents/PB_no.173_uPqYILM.pdf
[21] Ibid.
[22] NATO, Ibid.
[23] U.S. Department of Defense et al., Ibid.
[24] OST Ibid.
