A little-known Cold War treaty on outer space operations could draw the United States into direct conflict with Russia. Under Article VI of the Outer Space Treaty of 1967 (OST), states “bear international responsibility for national activities in outer space,” even when those activities are carried out by “non-governmental entities,” like commercial companies. States must first grant “authorization” for activities of non-governmental entities in outer space. The liability that follows is absolute, and attaches to any potential consequences of national activities conducted in outer space, including the actions of non-government (i.e. commercial) actors.

The United States, Russia, and over 100 other states are party to the OST, which remains in force and can be understood as a de facto constitution for space operations. That means the United States may be legally liable for the activities of services such as Starlink, a U.S. commercial satellite operated by SpaceX.

Well over a year into Russia’s full-scale conflict in Ukraine, Western countries continue providing critical, near-real-time information to Ukraine, including imaging data from satellites depicting troop movement, for example. Some of this information may be used by Ukraine to frustrate Russian attacks. Russia, in seeking ways to cripple aid and support to Ukraine, ironically refers to international law, which they blatantly violated by initiating the war and in so many instances during its conduct. Still, as the West grapples with justified and legitimate support to war-stricken Ukraine, NATO States tread a fine line. The success of humanitarian aid and defensive operations owes a lot to companies such as Starlink. But uses for military purposes, like direction of fires or target selection, complicate the calculus.

Not only does the OST require that States provide authorization to non-government actors for their outer space activities, but it also requires “continuing supervision” by the overseeing State (Article VI). Whether the U.S. government issued any guidance to Starlink is unclear. Starlink certainly is well aware of the issue, in spite of the Pentagons alleged concerns about the risk of SpaceX refusing to offer its services in support of Ukraine, recognizing the role of such commercial space operators in war efforts. However, since the liability for their actions may fall on the United States, the risk of becoming a party to an armed conflict with Russia is more than theoretical. For example, if Starlink is used to communicate with drones on the battlefield, its infrastructure may technically function as an element of a weapons system. If that is so, then Starlink satellites could potentially face the risk of becoming valid military objectives, as any weapons systems used in a conflict may become, if it provides an “effective contribution to military action” (Article 52(2) of AP-I, which is considered customary law). This is perhaps why Starlink has decided to curb such uses, although it is unclear how they did so technically.

The United States naturally desires to avoid becoming party to Russia’s conflict with Ukraine, At the same time, the United States clearly supports Ukraine in the conflict, which is evident in light of its information sharing initiatives and extensive arms supplies, including via the critical Polish hub. Likewise, Starlink officials worry about the consequences of their contributions and have considered or even limited the provision of internet connectivity to drones on the battlefield. It might mean an unfortunate limitation of Ukraine’s capability to defend its country. SpaceX CEO Elon Musk has stated that he prefers to avoid “World War 3”. While such rhetoric may be extreme, there are real grounds for concern.

As noted above, this is due to the Cold War-era Outer Space Treaty, concluded at the climax of nuclear weapons confrontation fears. It is understandable that in 1967 nobody imagined the thriving commercial space sector we have in 2023. It was perhaps uncontroversial to directly make States legally liable for the outer space activities of commercial and other non-governmental entities. Today, we live with the consequences of these decisions. Although modern uses of outer space are continuously challenging the original prescriptions of the OST, the treaty itself introduces stability in operations in orbit and sets out important bare minimum obligations for regulating the conduct of States in outer space. The question remains whether the OST’s existing provisions may be exploited in Russia’s conflict in Ukraine.

Russia already signaled that it may perceive uses of commercial space infrastructure as involvement in an armed conflict. The warning signs are in the form of legal, formal, and diplomatic notes. Russia issued a formal statement in September 2022 in the United Nations forum of the Open-Ended Working Group on Space Threats (OEWG), indicating an alleged perception of the “involvement of the U.S. and their allies’ civil infrastructure components in space, including commercial, for military purposes.” In the view of Russia, “such activities constitute indirect participation in armed conflicts.” Strikingly, the statement continued that such a “quasi-civil infrastructure may be a ‘legitimate target’ for retaliation.” This constitutes a rather overt, formal warning issued to the United States. While phrased in diplomatic-legal communication, it is nevertheless concerning.

In 2023 Russia argued that the body of law governing armed conflicts, International Humanitarian Law, or IHL, is inapplicable to military operations in outer space. Curiously, China – while not directly ruling out the application of IHL – expressed a similarly reserved opinion about these principles in space warfighting. At the same time, all Western countries agree that IHL does apply. These laws include important protections for civilians and civilian objects. The important IHL principles of distinction, proportionality, and precaution may well be applicable in outer space operations (at least in the opinion of the ICRC and the United States). Yet, given the inherent dual-use nature of some space infrastructure (like satellites), it may indeed be challenging to draw the lines. The ICRC is calling for doing the simple thing: registering objects with unambiguous purposes of use (to avoid the “dual-use” puzzle, where possible), in line with the Registration Convention, as per requirements in Article IV(1)(e) (i.e. the need to specify the “general function of the space object”). In any case, any military operations must remain proportional to the military goals sought and avoid excessive harm to civilian persons or objects. Denying the applicability of such rules of the road makes it unclear what would guide Russia in “retaliation.”

While the UN Charter’s article 2(4) prohibits using force without UN Security Council authorization, article 51 allows for national and collective self-defense. Thus, any resort to use of force by Russia against a country participating in the aid of Ukraine would be unlawful as a jus ad bellum matter. But given Russia of course denies that it is the clear aggressor in the conflict, it may “retaliate” through armed force despite its illegality, instrumentally using international law clauses to “justify” its actions.

In policy terms, what may happen is a matter of resolve and capabilities. Assuming a retaliation directed at space infrastructure, downing a Starlink satellite is imaginable. Russia has kinetic, anti-satellite missile weapons, and demonstrated their capability a few months before the start of the war. The effects would be dire for the whole world. Space debris from the destruction would complicate the use of outer space for all States, including Russia. Such a move would therefore be a powerful signal of irresponsibility: a deterrence move. (Legally, creating additional space debris may render such an attack disproportionate.) It is not clear whether, or how, the United States would respond to such actions. While U.S. Space Force may position itself as a capable force, a response-in-kind –the downing of a Russian satellite — would carry obvious results in the additional buildup of space debris, which would be highly unfortunate and likely escalate the conflict. That would suggest that the responses, if any, may be in a different domain.

Aside from targeting a Starlink satellite, Russia could also consider so-called RPO, rendezvous, and proximity operations, where Russian offensive satellites in space cause interference to U.S. satellites. Russia likely tested an RPO capability. It is still unclear whether it is available on demand. Objects in orbit remain defenseless. France is the only State so far that announced a plan to equip its satellites with offensive guns. But whether U.S. satellites already have such capabilities is unclear.

Another feasible option is retaliation with powerful cyberattacks. On the eve of its land invasion in 2022, Russian military cyber operators crippled the KA-SAT satellite internet system. Cyberattack responses need not be confined to space targets.

Considering effective deterrence, the most likely, if globally unfortunate, retaliation would be the downing of a single Starlink satellite. It is clear that effectively downing a whole Starlink constellation is not possible, as it is sufficiently big to avoid any realistic risk of destruction, and as such the military operation would unlikely yield military gains, rendering it unlawful as an IHL matter. Furthermore, replacing a satellite is easy. Would the ineffective action be symbolic, then? Any potential action might be meant to send a political message, and possibly function as a signal that more sensitive satellites may be next.

The U.S. reaction to a demonstration of force in space is another point of concern potentially putting the world on a dangerous trajectory. With the unilateral U.S. vow not to perform ASAT tests, U.S. hands seem to be tied in that respect. Especially due to the fact that a tit-for-tat response would simply contribute to the creation of even more space debris, such a move would demonstrate resolve, but it would be equally irresponsible.

With Russia sending overt threats, U.S. policymakers must be wary that the activities of commercial U.S. satellites are directly attributable to the United States. Contingency plans on the eventuality of the downing of satellites must be made. Meanwhile, States should continue to work on confidence building measures: States should unambiguously register their satellites to avoid erroneously falling in the dual-use trap. It is less clear how to restrain electronic warfare or cyberattacks in space. The idea put forward by some States to restrain proximity operations is also tricky to implement, given future needs of on-orbit servicing, such as refueling or repair, technically require conducting proximity activities. But nothing (legally, technically) constrains kinetic destruction, which carries unambiguously negative effects. Whether through a UN Security Council mandate or a new treaty, States should ban anti-satellite tests, which are harmful to humankind. We may be witnessing the emergence of a space norm that would prohibit ASATs, with States such as the United States, France, Japan, Brazil (very elaborately) and many others endorsing it. All States must accept the restraining guarantees of international humanitarian law as applicable in outer space. Lastly, waging a kinetic war in outer space would contribute to making it much more difficult for humankind to benefit from outer space in the future, not least because of the accumulation of space debris in Earth’s orbit. Any kinetic destruction of a space object creates additional pieces of space debris. In the extreme, the buildup of debris could make outer space unusable. Hopefully, these consequences would be a restraining motivation for every potential belligerent.

IMAGE: Spacecraft Launch Into Space. Elements of this image furnished by NASA.