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  • Noam Neuman

Heavy Gravity: An Expanding Arms Race in Space Challenges Int'l Law

The steady advance in states’ outer space military capabilities raises concerns about extraterrestrial conflicts in the near future. Despite this danger, states cannot seem to agree on new rules of international law to govern military operations in space. Two legal manuals on the matter are expected to be published this year, but international law on military operations in space is likely to be determined by the evolving practice and legal positions of the states operating in this domain

Image created with the assistance of DALL·E 2

More than five decades after the Outer Space Treaty[1] (OST) came into force and roughly thirty years after the First Persian Gulf War, which many experts have dubbed "the first space war," there is a growing likelihood that armed conflict will escape Earth’s gravity in the near future and make it to outer space.[2] This prediction is reinforced by several occurrences over the last few years: (1) the establishment of "space commands" by several states, whose aim is to manage military operations in outer space; (2) states' publication of strategies and policy resolutions relating to military operations in space; and (3) the growing number of experiments of a military nature conducted beyond the atmosphere.

Having war reach outer space raises many concerns. While the OST includes specific restrictions on certain military activity in space, it does not explicitly ban or regulate most aspects of military operations in that domain. As a result, a great deal of effort has gone into negotiating multi-national, legally binding pacts restricting military operations in space beyond the accords reached in the 1960s within the framework of the OST. However, these efforts have yet to yield concrete results.

The challenge in formulating rules of international law that would apply to military operations in space is all the greater given the unique features of war in space, when compared to traditional spheres of war on land, at sea, and in the air. These include the absence of elements such as water and oxygen and an atmosphere influencing air pressure or temperature regulation; the lack of defined geographical routes, which would enable, among other things, borders to be determined; the absence of friction, enabling objects to move quickly with minimal hindrance; and varying gravitational forces, which affect the amount of energy and resources required to move in an area.

Furthermore, outer space is a hostile environment where human control is limited, as is the ability to assess the risks involved. Consequently, the cost of research, development, and of launching forces and materiel into space is significantly higher, rendering routine maintenance especially challenging.[3]


Other than these restrictions agreed upon roughly half a century ago, there exist no other prohibitions on military activity in outer space


Given these circumstances, two groups of experts have been working in recent years on manuals whose aim is to survey the codex of international law applicable to military operations in space. This author is a member of one of these groups, developing the Woomera Manual on the international law of military space operations.[4] A second group is working in parallel on an additional manual on this topic.[5] Both manuals are expected to be published later this year.

In this review, I will briefly outline the main treaties regulating what states may and may not do in space (commonly referred to as "space law"), as well as the development of space as an arena of war and the steps taken (unsuccessfully, so far) to prohibit or restrict the militarization of space. In this context, I will address some of the efforts currently being taken by states to reach a consensus regarding possible norms, rules, and principles of responsible behaviors with respect to outer space military activity.

As mentioned above, alongside the efforts made by states in international forums, other significant initiatives aim to compile academic manuals intended to provide an objective restatement of international law as applied to military operations in space. I will also touch upon these initiatives while explaining how certain factors – such as the unique features of outer space and the need to bridge, in some areas, the gaps between space law and international law regarding military activity – make these efforts particularly complex. To illustrate these complexities, I will briefly analyze four dilemmas in applying international law to outer space military activities. Finally, I will discuss how these manuals are expected to be received by states as they formulate their positions concerning these issues.

Space law – main principles

In the 1960s and 1970s, several treaties regulating state operations in space were concluded, acknowledging the "common interest of all mankind in the progress of the exploration and use of outer space for peaceful purposes."[6] The 1967 Outer Space Treaty is the most important of these texts, as it sets forth the main principles of space law. It has been augmented over the years by additional treaties relating to specific issues: the 1968 Agreement on the Rescue of Astronauts, the Return of Astronauts and the Return of Objects Launched into Outer Space (the Rescue and Return Agreement);[7] the 1972 Convention on the International Liability for Damage Caused by Space Objects (the Liability Convention);[8] and the 1975 Convention on Registration of Objects Launched into Outer Space (the Registration Convention).[9]

According to the OST, outer space, including the moon and other celestial bodies in it, shall be "the province of all mankind" and "is not subject to national appropriation by claim of sovereignty, by means of use or occupation or by any other means."[10] Therefore, no state may declare any area in space as being under its control, and cannot wield its laws and sovereign powers there.[11] Moreover, astronauts in space are considered envoys of all mankind, and every state is required to protect them and render to them all possible assistance in the event of accident, distress, or emergency landing on the territory of another State Party or on the high seas.[12]

The OST also provides that the use of space must comply with international law, including the Charter of the United Nations, "in the interest of maintaining international peace and security and promoting international cooperation and understanding."[13] However, the treaty does not clearly define the term "peace," and various states and commentators disagree on the extent of the restriction. The prevailing view is that the constraint is confined to "aggressive use" of space, i.e., use that does not comply with the UN charter,[14] though some contend that the extent of the prohibition is broader.[15]

In addition, the OST provides that operations in space shall be guided by principles of cooperation and mutual assistance, and they must be conducted with “due regard” to the interests of other states. Accordingly, states are required to avoid "harmful contamination" of space, to allow other states to monitor the launch of an object that a certain state plans to send into space, and to consult with one another where planned activity in space is likely to cause potentially harmful interference with the activities of other states party to the treaty. [16]


Though the militarization of space has dramatically intensified since the 1990s, efforts to regulate these activities have so far failed


Furthermore, the OST states that the parties "shall bear international responsibility for national activities in outer space... whether such activities are carried on by governmental agencies or by non-governmental entities." For this purpose, states are required to authorize and continually supervise the activity of private entities operating in space. [17]

The OST also addresses several aspects of military activity. It prohibits, inter alia, placing any objects bearing weapons of mass destruction in space and stationing bases, holding military experiments, and carrying out military maneuvers on, and in, celestial bodies. Nevertheless, the treaty clarifies that the use of military personnel for scientific research or for any other peaceful purposes may not be prohibited.[18]

Other than these restrictions on military activity in space, stemming mainly from the agreements that states (with emphasis on the United States and the Soviet Union) reached roughly half a century ago, there exist no other prohibitions in the OST or any other specific regulation on the possibility of military activity in outer space.

The militarization of space has dramatically intensified since the 1990s. Under these circumstances, attempts were made to formulate internationally agreed upon binding treaties, or non-legally binding norms and/or rules in support of the existing legal framework. The next section discusses these initiatives.

Diplomatic attempts at regulation

The militarization of space is a decades-old phenomenon. During the First Gulf War in 1991, the U.S. army made extensive use of satellites for espionage, communications, and location (GPS), all of which contributed significantly to the defeat of Saddam Hussein’s Iraq.[19] Since then, numerous states have continued to rapidly develop their abilities in space, including relying on private space enterprises (dubbed “NewSpace”),[20] with the aim of achieving superiority over their rivals.[21] The importance of satellites for military activity, and the military’s reliance on them was recently illustrated during the Russia-Ukraine war.[22] Therefore, it is likely that in the future we will continue to witness a heavy reliance by parties to conflicts on space objects, as well as attempts to disrupt opponents' access to satellites.

At the same time, we are witnessing a process termed the “weaponization of space,”[23] in which states pursue technological developments and conduct experiments not only to exploit the military advantages arising from fielding satellites in support of ground, sea, and air-based military operations (a process termed "militarization of space"), but also to place space-based devices with destructive capacities in orbit or sub-orbit. This is exemplified in recent years by two significant trends: the rise in the number of military experiments conducted in space, and the establishment of special army units whose entire purpose is to execute military activity in space.

The growing extent of military experiments is evident in the number of states conducting them, and the expansion of the scope of these experiments. For example, in March 2019, India carried out a test launch of anti-satellite missiles (ASAT), thereby joining China, Russia, and the U.S., which had previously conducted such tests. In October 2021, China reportedly carried out a test launch of a hypersonic missile capable of leaving the atmosphere, orbiting the planet, and upon command, returning to attack Earth. The last ASAT missile test was conducted in November 2021 by Russia, against one of their own retired satellite (the Cosmos 1408, which became obsolete in the 1980s). Russia has also carried out several robotic rendezvous and proximity operations (RPOs),[24] in both low earth orbit (LEO) and Geostationary earth orbit (GEO), most of which are related to military operations. Finally, the U.S. has been carrying out tests using the X-37B orbital test vehicle for years.

In addition, some states have begun to set up special units responsible for military activity in space and to consolidate doctrines for their national interests in space. For example, in December 2019, the U.S. set up its Space Force and, in June 2020, it compiled a strategy paper that explicitly stated that Russia and China pose significant threats to its activity in this realm.[25] In 2019, France established a Space Forces Command and in October 2021 it carried out its first military exercise, which included a scenario in which a foreign space object threatened one of its satellites.

In September 2021, Britain published an updated national strategy paper regarding its activity in space. The document set a goal of defending and preserving Britain's national interests in space and clarifies that London views it as a possible domain for military activity. During the NATO summit in June 2021, the leaders of the member states declared (paragraph 33) that "attacks to, from, or within space present a clear challenge" to the security and stability of the Alliance in a manner that may justify the invocation of Article 5, the organization's collective defense mechanism.

A Rand Corporation guide to hypersonic missile nonproliferation | Source: Youtube

Given the concern about an arms race in space, several attempts have been made over the years to formulate consensual rules on the matter – either through a new legally binding treaty or, more feasibly, through a set of non-legally binding norms, rules, and principles. Since 2008, China and Russia, the main proponents of negotiating a new legally binding treaty, have been pursuing an international treaty prohibiting arms from being placed in space and the threat or use of force against objects in space.[26] Additionally, in 2017, the UN General Assembly appointed a Group of Governmental Experts (GGE) to "consider and make recommendations," based on consensus, "on substantial elements of an international legally binding instrument on the prevention of an arms race in outer space, including, inter alia, on the prevention of the placement of weapons in outer space.” [27] However, given the mistrust between the blocs (especially between the United States versus Russia and China), these efforts did not bear fruit.

In addition, several attempts have been made to reach a consensual agreement regarding non-legally binding principles, norms, and rules. For instance, in 2010, the UN General assembly adopted a resolution in which it decided to establish a Group of Governmental Experts (GGE) tasked with conducting a study on outer space transparency and confidence-building measures (TCBMs).[28] In 2013, the GGE submitted a report[29] – agreed upon by consensus – which presented a set of transparency and confidence-building measures for outer space activities for states to implement on a voluntary basis.

In recent years Britain and other Western states promoted an initiative to formulate norms, rules, and principles for responsible behavior in space. This lead to the adoption on UNGA resolution 75/36, which called on states to submit views to the Secretary General on what activities "could be considered responsible, irresponsible or threatening."[30] In accordance with that resolution, in July 2021 the UN Secretary General published a report reviewing the positions of twenty-five states and the European Union.[31] Subsequently, and pursuant to General Assembly resolution 76/231,[32] an open-ended working group (OEWG) on reducing space threats through norms, rules and principles of responsible behaviors was established. The OEWG’s work is currently underway.[33]

Finally, in December 2022 the UN General Assembly adopted three more resolutions on this subject. The first resolution calls upon all states to commit not to conduct destructive direct-ascent anti-satellite tests, i.e., launching missiles from the surface of the Earth intended to destroy a specific satellite.[34] The second resolution, adopted the same day as the first, invites the Conference on Disarmament "to establish a working group under its agenda item entitled 'Prevention of an arms race in outer space' as early as possible."[35] Lastly, the third resolution requested the establishment of another UN Group of Government Experts (GGE) to "consider and make recommendations on substantial elements of an international legally binding instrument on the prevention of an arms race in outer space."[36]

The mounting fear that warfare will seep into space, and the inability of the international community to formulate consensual norms, rules, or legally binding instruments on the matter, have in recent years led groups of independent experts to promote two initiatives to compile law manuals. In the next section, I will discuss these manuals.

Military activity in space: Designing legal manuals

The purpose of the legal manuals for military activity in space, which the two separate groups of independent experts have been working on in recent years, is to articulate and objectively clarify the existing rules of customary international law applicable to space activities.[37]

Manuals of this type are interpretive "soft" documents that, while not legally binding, can have a great deal of influence over international discourse, since they often serve as a starting point for statements and treatment by states. A few prominent examples are the San-Remo Manual on International Law Applicable to Armed Conflict at Sea (1995), the HPCR Manual on International Law Applicable to Air and Missile Warfare (2009), and the Tallinn Manuals on the International Law Applicable to Cyber Warfare (2013 and 2017).[38]

The two upcoming manuals do not purport to deal with space law exhaustively but rather focus on its military aspects. The McGill Manual on International Law Applicable to Military Uses of Outer Space (MILAMOS) focuses on aspects of international law relating to the military use of space during peacetime, while the Woomera Manual Project articulates and clarifies existing international laws applicable to military space operations, both during peacetime and during armed conflict. These manuals are expected to tackle complicated questions, including how to correctly interpret and apply space treaties to military activity in space.

To illustrate the difficulties in applying existing legal rules to military activity in space, I will now delve into four scenarios highlighting dilemmas that typically arise regarding the application of international law to military operations in outer space.

(1) Applying the right to self-defense in reaction to an attack on a satellite

A relatively simple scenario generating debate in the international arena is a situation in which State A launches an anti-satellite missile (ASAT) that hits a military satellite owned by State B outside of an ongoing conflict.

State operations in space are subject to the provisions of international law, including the UN Charter.[39] Among other things, Article 2 of the Charter calls on nations to resolve their conflicts peacefully and avoid the "threat or use of force." Article 51 of the Charter provides an exception, which enables nations to defend themselves against an "armed attack." Accordingly, launching an ASAT missile would appear to constitute forbidden use of force against State B, probably amounting to an armed attack, and thus enabling the afflicted country to react in self-defense against State A.[40]

While the answer in this scenario is quite straightforward, it becomes inherently more complex if State A takes offensive action that causes State B’s satellite to stop operating but does not physically damage or destroy it. In such a case, there is a dispute over whether the action can be considered a use of force or even an armed attack.[41]

Does incapacitating a satellite - without physically damaging it - constitute an armed attack? | Illustration: PIRO4D on Pixabay (Pixabay licsense)

When this conundrum was debated in the context of offensive cyber-ops, some states (including Israel) and experts opined that the accepted interpretation of the terms "use of force" and "armed attack" must involve physical damage.[42] Under this interpretation, a computer network attack (CNA) that shuts down a computer system but does not physically harm any of its components will not be considered a use of force or an armed attack. Other states and experts, however, thought that in some circumstances, a cyber-attack that causes a computer or network to stop working permanently, or damages essential national infrastructure, can also constitute a use of force and, sometimes, even an armed attack.[43]

This raises the question of how states will address this issue in the context of action taken in outer space, taking into account that satellites are much more vulnerable to external interference (for example, an object that maneuvers toward a satellite and blocks its solar panels could cause the latter to stop functioning), and that repairing them would require the allocation of a great deal of funding and resources.

Another complex conundrum is the question of which state has the right to defend itself against an armed attack on a satellite. In other arenas of war, the answer is more clear-cut. For example, under customary international law, when an armed attack is mounted from within a vessel in the high seas, the right of self-defense belongs to the state whose flag the attacked vessel is flying.[44]

If that rule is applied to space, then the right to self-defense would belong solely to the state that registered the satellite upon its launch. However, the Convention on the Law of the Sea rule applies only to the maritime domain. The OST never regulated this aspect, and there could be different approaches to the question. Thus, for instance, one could claim that given the special arrangements determined in the OST regarding the "launching state," the right of self-defense could belong both to the state which the attacked satellite is registered under and to the one which launched it into space. One could further argue that even a state not considered the "launching state" could nevertheless have the right to self-defense if the attack targeted a satellite supplying it with military services.[45] In any case, at present, this question seems to have no clear answer.

(2) The regime of State responsibility in space and its application in the context of military action

In another scenario, a private enterprise located in the territory of State A owns a satellite that supplies military services to the armed forces of State B, which is engaged in an armed conflict with State C. These services grant the armed forces of State B a significant military advantage in the fight.

The law of neutrality regulates the relations between nations that are parties to an international armed conflict (States B and C, in this case) and neutral states not involved in the conflict (State A). Pursuant to the law of neutrality, a neutral state may not supply a belligerent state with ammunition or "war material of any kind." Does this signify that State A must prevent the private enterprise from supplying military satellite services to State B?

Based on the law of neutrality, the answer would seem to be negative. The reason is that the prohibition on supplying war material does not require neutral states to prevent the "export or transit" of arms or "anything which can be of use to an army" by private entities.[46] As a result, in our scenario, State A – in which the enterprise operates – could claim that this also applies to military services provided by a private enterprise via satellites it launches into space.

However, these are not the only laws that could apply to the circumstances. In response, State C could invoke the special rules in the OST, under which member states are responsible for the "national" activity carried out in space by commercial companies operating within their territory.[47] Accordingly, State C could argue that the military services provided by that private enterprise could be seen as being provided by State A itself, in contravention of the law of neutrality.[48]

In a similar scenario, a private enterprise operating a satellite registered under State D could use it for an action tantamount to the prohibited use of force against State E, without State D's knowledge. In that instance, it could be argued that the special rules under the OST should apply and that consequently, State D should be viewed as responsible for that action, with all that this implies.

As a counterargument, one could claim that under "The law of State responsibility" in international law,[49] the registered state would be responsible for the private enterprise's action only in cases where the enterprise is operating at the state's instruction or under its control.[50] Here, too, opinions may differ regarding the interpretation of the responsibility rule in the OST and its relationship with the general rules of state responsibility in international law.

(3) Application of the law on armed conflict in space, given its unique environmental conditions

In another scenario, States A and B are engaged in armed conflict. At some point, State A decides to attack one of State B's military satellites using an anti-satellite (ASAT) missile. In contrast with scenario (1), which dealt with the legality of the use of force in peacetime (jus ad bellum), the present scenario involves the legality of attacks in the context of an armed conflict (Jus in bello, also known as "the laws of armed conflict" or "international humanitarian law".)

The laws of armed conflict were formulated in respect to the traditional domains of war – land, sea, and air. However, the prevailing opinion is that they can be applied to space as well. This approach relies, among other things, on the 1996 advisory opinion of the International Court of Justice (ICJ) on the legality of the threat or use of nuclear weapons, under which the law of armed conflict applies to "all forms of warfare and to all kinds of weapons."[51] This opinion is shared by various states, international organizations such as the International Committee of the Red Cross (ICRC), and academics.

In any case, even if the laws of armed conflict need to be applied also to space warfare, how they ought to apply is not always clear, given the unique characteristics of this domain.

An ASM-135 anti-satellite missile. Does its use comply with the principle of proportionality? | US Air Force Photo by Ken LaRock

For example, as the ASAT attack described in this scenario will probably be considered as an “attack” under the law of armed conflict, it would be subject to its relevant principles, including the principle of distinction, the rules regarding precautions in attack, and the principle of proportionality.[52] Applying these criteria to space warfare raises interesting questions, such as how the "space debris"[53] resulting from such ASAT attack needs to be treated under the law of armed conflict.

On the one hand, space debris is likely to spread over vast areas, thus reducing the probability that it will damage a functioning satellite or an active space station.[54] As a result, one might argue that the space debris created by the attack should not be considered "collateral damage."

On the other hand, given the growing amount of space debris, many fear that at some stage, new debris will cause a collisional cascading of objects in space (which is known as the Kessler syndrome), potentially damaging active satellites and endangering human ability to operate in that area of space.[55] Some, therefore, might argue that when considering the collateral damage resulting from such an attack, the attacking entity must also consider the cascading threats that the space debris likely to be created would pose to civilian space objects.

If that claim is accepted, then State A would have a duty to consider alternative means that would allow it to disable the enemy satellite without producing so much debris,[56] or even to refrain from the attack entirely if the expected collateral damage from these cascading threats will be considered as excessive (i.e. not in accordance with the principle of proportionality)[57] when weighed against the direct anticipated military advantage gained by it.

Another related question is whether space should be seen as a "natural environment." Several experts contend that the law of armed conflict prohibits states from employing means and methods of war that are intended, or likely, to cause widespread, long-term, and severe damage to the environment.[58] Some commentators and states argue that space should also be protected by this rule.

(4) Interfaces between space law and the law of armed conflict regarding military activity in space

Complex issues are also likely to emerge when the potential application of two bodies of law – in this case, space law and the law of armed conflict – leads to different outcomes. In this context, one of the questions likely to arise is which of these systems of law constitutes specific subject matter (lex specialis) that prevails over the more general law (lex generalis).[59]

Take for example a scenario in which States A and B are engaged in an armed conflict. State A decides to attack State B's space station, which houses astronauts who belong to its armed forces. On the one hand, space law views the astronauts as "envoys of humankind" who should be treated with caution and assisted in the course of their routine activity in space, and even – when in distress – returned to their state healthy and unharmed.[60] These laws also explicitly enable states to employ military personnel for research purposes or any other peaceful activity.


The problem presents itself when applying the law of armed conflict to military activity in space leads to different results than by applying space law


On the other hand, under the law of armed conflict, members of a state's armed forces are considered combatants who may be lawfully attacked and, if captured, held as prisoners of war. It is therefore unclear whether State A is permitted to attack the astronauts of State B in the abovementioned space station, or whether they should be protected.

Another related question is whether State B can sue State A for damages to its space station in the context of an armed conflict. At first glance, the question may sound far-fetched: under the law of armed conflict, if an attack was carried out against a military target during an armed conflict, the attacking state does not have to pay compensation for the damage caused to the target.

However, according to the liability rules in space law, a state may be required to compensate another state, international organization, or even private enterprise for the deliberate damage it caused to their property in outer space "if the damage is due to its fault or the fault of persons for whom it is responsible."[61] Though the law of armed conflict would seem to prevail in this case, claims could be raised that would limit its scope.

These examples illustrate that applying the law of armed conflict to military activity in space may sometimes lead to different results than would be reached by applying space law. Accordingly, it bears considering further deliberation on which laws would prevail under such circumstances.

Summary and conclusions

Discussions surrounding military operations in space have been gaining momentum in recent years. Understandably, there is genuine concern that military conflicts will spill over to space in the foreseeable future. Nations understand this danger, yet despite the general sense that most would prefer things to be different, they continue to build their military capabilities in this domain.

Under these circumstances, a debate on international norms and on the rules applying to military activity in space is crucial, inter alia, within the framework of the forthcoming Woomera and McGill Manuals. Even though these manuals will have no official legal standing, they could serve as a starting point for developing international discourse. Consequently, they are likely to influence the legal rules on such military activity, especially if states develop their practices and issue statements based upon, or in reference to, these manuals.

For this purpose, one can learn from the way discourse on the application of international law to cyber warfare has evolved in the last few decades. In its early stages, the discourse was conducted mainly between experts focusing on the positions set forth in the Tallinn manuals. However, in recent years, more and more states – Israel among them – have expressed official legal opinions on the matter, including within the framework of conferences of state experts and in UN forums. The positions taken by states have advanced the discourse and are likely to influence the development of international customary law regarding military activity in cyberspace.

We can expect a similar process regarding military activity in space in the coming years. States are likely to consider and review their positions on the legal questions regarding the space domain. They might also consider establishing agreed-upon norms, whether independently or via UN initiatives. At a later stage, some states may also consider whether the time has come for them to express their opinio juris on the matter. This might also be the case with Israel, which has a growing presence in outer space, and which engages in broad legal and diplomatic activities in this field.[62]


Noam Neuman is the head of the Law of Armed Conflict Division at the Israeli Ministry of Justice. He is a member of the international team of experts compiling the Woomera Manual on the International Law of Military Space Operations. The views expressed in this article are his own and do not necessarily reflect the position of the Ministry of Justice or the State of Israel. The author wishes to thank Adv. Mattan Gilboa for his assistance in writing this article.

(Photo: Israel Ministry of Justice, courtesy of the author)

Notes: [1] Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, 610 U.N.T.S. 205 (opened for signature 27 January 1967, entered into force 10 October 1967) – hereinafter "the Outer Space Treaty" or the OST.

[2] See for instance: Tory Shepherd, "Life no longer as we know it’: war in space would have devastating effects, military experts say", The Guardian, 28 November 2022, at; Henry Sokolski, "A China-US war in space: The after-action report", Bulletin of the Atomic Scientists, 17 January 2022, at: [3] See for instance: United States Space Force, Spacepower: Doctrine for Space Forces, Washington DC: United States Space Force, June 2020, at:

[4] A draft manuscript of the Woomera Manual was presented for state consideration during a State Engagement process, facilitated in the Hague by the Government of the Netherlands, during the period of 1-3 June 2022. Following this process and the comments received, the editorial board is working on the final manuscript of the manual, which is planned to be published later this year. See:

[5] Volume I of the McGill Manual on International Law Applicable to Military Uses of Outer Space (MILAMOS) was published on 12 July 2022. Volume II, which is set to include commentaries on the manual, is planned to be published later in 2023.

[6] In the introduction to the Outer Space Treaty.

[7] Agreement on the Rescue of Astronauts, the Return of Astronauts, and the Return of Objects Launched into Outer Space, (1968) 672 U.N.T.S. 119.

[8] Convention on the International Liability for Damage Caused by Space Objects (1972) 961 U.N.T.S. 187.

[9] Convention on Registration of Objects Launched into Outer Space (1975), 1023 U.N.T.S. 15. Note that there is an additional treaty regulating operations on the moon, but only eighteen states are parties to it, none of which are considered "space superpowers."

[10] Articles 1-2 of the Outer Space Treaty.

[11] An identical principle was laid forth in Section 4(2) article 71 of the Antarctic Treaty, 12 U.S.T. 794, 402 U.N.T.S. (1959).

[12] Article 5 of the Outer Space Treaty.

[13] Article 3 of the Outer Space Treaty.

[14] Most commentators and states, including the U.S. and USSR, interpreted the terms "peace" as "non-aggressive use," i.e., use that complies with the UN charter. See for instance Michael N. Schmitt, “International law and military operations in space,” in: A. von Bogdandy and R. Wolfrum (eds.), Max Planck Yearbook of United Nations Law Online, 10(1), 2006, pp. 89, 101-102.

[15] Some commentators and states, such as Argentina, India, and Iran, view the prohibition as applying to any military use.

[16] Articles 9-10 of the Outer Space Treaty.

[17] Article 6 of the Outer Space Treaty.

[18] Article 4 of the Outer Space Treaty.

[19] See for example Larry Greenemeier, “GPS and the World's First ‘Space War’,”Scientific American, 8 February 2016, at:

[20] This industry is led by multinationals, the most prominent of which is SpaceX, and reflects another aspect of the growing commercialization of outer space, especially as of 2017. Experts foresee that in the years to come, there will be a significant growth in the number of satellites launched into orbit around Earth, and that their output and the capabilities they are planned to supply will also serve for military purposes. This forecast came true in the Russia-Ukraine conflict, in which SpaceX provided Ukraine and its forces with a reliable source of satellite internet. See: “How Elon Musk has changed warfare,” The Economist, 11 January 2023, at:

[21] See for example: US Air Force Doctrine Publication 3-14, Counterspace Operations, 27 August 2018, p. 4, at:

[22] For example, in a recent panel session, the U.S. Space Force Chief of Operations emphasized the prominence of the use of space technology in the Russia-Ukraine war context. See:

[23] For a review of the development of the arms war in space, see, for example, Zeev Shapira and Gil Baram, "Arms Race in Space: Global trends and state interests", Cyber intelligence and Security, 3(2), October 2019, at:

[24] “Rendezvous and Proximity Operations” are a euphemism for actions in space using a body in proximity to another body that could disrupt the operations of the latter in the short or long term. For an explanation of RPOs and their implications for security in space, see for example Brian Weeden, “The Evolution of Space Rendezvous and Proximity Operations and Implications for Space Security,” presentation given at the United Nations Disarmament Conference, 12 April 2019, at:

[25] US Department of Defense, Defense Space Strategy Summary, June 2020, p .1.

[26] See, for example, the joint drafts from 2008 and 2014 on a "Treaty on the Prevention of the Placement of Weapons in Outer Space. The Threat or Use of Force Against Outer Space Objects (PPWT)."

[27] See UN General Assembly resolution 72/250.

[28] See UN General Assembly resolution65/68.

[30] Britain's proposal was advanced in the framework of the UN disarmament committee (the first committee) and passed in December 2020 as UN General Assembly Resolution 75/36 on contending with threats in outer space by setting norms, rules and principles for responsible behaviors (Reducing Space Threats through Norms, Rules and Principles of Responsible Behaviours). See:

[31] Aside from states, the initiative was addressed by nine non-state actors, including the International Committee of the Red Cross (ICRC), which among other things addressed the possible risks of armament in space and clarified that in its view, activity in this domain should be pursued in compliance with the principles of international law on the use of force and armed conflicts. See:

[32] See UN General Assembly resolution 76/231.

[33] The working group will convene in four sessions between May 2022 and August 2023. It is worth noting that there are also regional initiatives, such as the EU’s draft International Code of Conduct for outer space activities, but they have only limited effect.

[34] See UN General Assembly resolution 77/41.

[35] See UN General Assembly resolution 77/40. In this resolution, the General Assembly also recognized “the growing convergence of views on the elaboration of measures designed to strengthen transparency, confidence and security in the peaceful uses of outer space, without prejudice to efforts towards the conclusion of an effective and verifiable multilateral agreement or agreements on the prevention of an arms race in outer space.”

[36] See UN General Assembly resolution 77/250.

[37] For a rule in international law to be considered to have customary status, two components must exist: general practice by states, and statements by those states that view such practice as opinio juris. On this, see the UN ILC 2018 draft conclusions on identification of customary international law:

[38] Michael N. Schmitt (ed.), Tallinn Manual On International Law Applicable To Cyber Warfare, 2013; Michael N. Schmitt (ed.), Tallinn Manual 2.0 On The International Law Applicable To Cyber Operations, 2nd edition, 2017.

[39] Article 3 of the Outer Space Treaty

[40] In this respect, the United States has expressed on more than one occasion the importance in ceasing ASAT systems. For example, in April 2022, U.S. Vice President Kamala Harris announced that the United States “commits not to conduct destructive, direct-ascent anti-satellite missile testing”. See: A statement addressing the need to cease ASAT systems was also given by the U.S. to the open-ended working group on reducing space threats. See:

[41] The common approach recognizes a gap between the two terms and sets an armed attack at a higher bar than the use of force. However, the extent of this gap is disputed.

[42] See for instance the Israeli position published in December 2020 at the US Naval War College conference: Roy Schondorf, “Israel’s perspective on Key Legal and Practical Issues Concerning the Application of International Law to Cyber Operations,” EJIL Talk!, 9 December 2020, at:

[43] See for instance the French position published in September 2019, paragraph 1.2.1; see also the Tallinn Manual 2.0, p. 343.

[44] Article 91 of the UN Convention on the Law of the Sea. Note that Israel is not a party to that treaty, but many of its provisions, including this one, are considered to represent customary law. See, for example, "Oil Platforms (Islamic Republic of Iran v United States of America)," Judgment, ICJ Reports 2003, p. 161, para. 64.

[45] The term "launching state" is defined in Article 1 of the Registration Convention and relates to both possibilities.

[46] The main condition is that the sale be done by that enterprise equitably, without the country in whose territory it operates forbidding said enterprise from selling the means to specific countries. For elaboration on the neutrality law in the context of cyberspace, see: Noam Neuman, “Neutrality and Cyberspace: Bridging the Gap between Theory and Reality,” International Law Studies, Vol. 97, 2021, pp. 765-802, at:

[47] Article 6 of the Outer Space Treaty. Note that this responsibility regime is also mentioned in later resolutions in the context of space. See for example Articles 8 and 9 of UNGA Resolution 37/92 on the principles for television broadcasting from satellites.

[48] Iran, for example, on 25 November 2022 sent a letter to the UN Office for Outer Space Affairs, in which it criticized the "illegal internet operation of Starlink within the territory of the Islamic Republic of Iran by the Space Exploration Technologies Corporation of the United States of America (SpaceX), with United State Government support." For further reading, see: Mike Wall, “SpaceX reveals ‘Starshield’ satellite project for national security use,”, 7 December 2022, at:

[49] Article 2 of the Responsibility of States for Internationally Wrongful Acts, with commentaries, 2001, which many see as reflecting customary international law.

[50] Ibid, Articles 2 and 8. Regarding the possibility of casting responsibility because of existing "control," opinions differ – in court rulings and among commentators – regarding the extent of control required to establish such responsibility.

[51] See especially paragraphs 86 and 89 of the council's opinion.

[52] See, for example, Emanuela-Chiara Gillard, “Proportionality in the Conduct of Hostilities: The Incidental Harm Side of the Assessment,” Research Paper, Chatham House, 10 December 2018, para. 22; Michael N. Schmitt, “’Attack’ as a Term of Art in International Law: The Cyber Operations Context,” in: Christian Czosseck, Rain Ottis & Katharina Ziolkowski (eds.), Proceedings Of The 4th International Conference On Cyber Conflict, 7 September 2012, pp. 283, 285-286, at SSRN:

[53] "Space debris" are objects manufactured by humans that serve no purpose anymore, including parts and components locked in Earth's gravitational orbit. An ASAT missile attack on a satellite could result in thousands of pieces of space debris orbiting Earth for a long period.

[54] In this context, it bears keeping in mind that many operational satellites are maneuverable in order to enable them to evade exactly such damage.

[55] "Report of the Secretary General on Reducing Space Threats through Norms, Rules and Principles of Responsible Behaviors," UNSGOR, UN Doc A/76/77 (2021), para. 13.See in this context the position of the RAND corporation:

[56] See, for example, ICRC report on IHL and the Challenges of Contemporary Armed Conflicts: Recommitting to Protection in Armed Conflict on the 70th Anniversary of the Geneva Conventions, 22 November 2019, p. 34, at:

[57] Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), 8 June 1977, Art. 51(5)(b).

[58] The protections are listed, inter alia, in Articles 35 and 55 of the 1977 First Additional Protocol to the Geneva Conventions and all the countries party to the protocol are bound by them. Israel, which is not party to the first protocol, believes that these protections do not have customary status – and therefore do not obligate states that are not party to the protocol.

[59] The institution of lex specialis is a rule in international law to prioritize among laws, under which the specific law overrides more general laws when they conflict. On this matter, see Article 55 of the draft rules of state responsibility. However, regarding military activity in space, a unique situation arises in which two distinct systems of law – the one regulating military activity during armed conflicts, and another regulating human activity in outer space– may be considered "special," each in its area. Accordingly, it is not clear which would be the lex specialis that overrides the other.

[60] Article 5 of the Outer Space Treaty and Article 4 of the Rescue and Return Agreement.

[61] Article III of the Liability Convention.

[62] For example, in 2022 Israel signed the Artemis Accords, which includes sections relating to joint research for the exploration of space and for peaceful civilian activity on the moon and Mars, and in regard to comets and asteroids.


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