8.1.1 Kinetic ASAT Weapon Tests This Century

As soon as the first satellites were placed into orbit, states began exploring how to destroy them, with the first kinetic ASAT weapon test taking place as early as 1959. These efforts were led by the United States and the Soviet Union, with China and India following in the 2000s. A comprehensive list of ASAT weapon tests, made available by the Secure World Foundation, is worth taking time to review online.Footnote ²⁷

Several things can be learned from the Secure World Foundation list. First, most ASAT weapon tests have generated no Space debris, mainly because they were conducted without a physical target. Second, those that have involved strikes on physical targets have generated debris, and in doing so have had a lasting impact on the orbital environment. Third, single events, such as the 2007 Chinese ASAT weapon test, can create substantial changes to the debris population. Fourth, the cumulative effects of multiple events can also be serious and long-lasting. Indeed, there are about as many fragments from Soviet-era ASAT weapon tests still in orbit today as there are fragments added by the November 2021 Russian ASAT test. And when those two debris populations are added together, they are comparable in number to that produced by the 2007 Chinese test, the single worst debris-generating event of all time.

As states have become aware of the long-term Space debris created by ASAT weapon tests, and the associated hazards, opposition to those tests that involve physical strikes has also begun to grow.

8.1.2 Responses to the 2007 Chinese ASAT Weapon Test

The 2007 Chinese test was the first strike by a kinetic ASAT weapon in more than two decades.

It could be argued that the debris-creating test, as a prominent instance of ‘subsequent practice’, confirmed and thus bolstered an interpretation of the Article I, second paragraph, freedom of exploration and use that allows for such testing. But an examination of the international response to the test leads to a different conclusion.

Any assessment of subsequent practice associated with an ASAT weapon test must also include the responses from other treaty parties because, in accordance with Article 31(3)(b) of the Vienna Convention on the Law of Treaties, we are looking for ‘any subsequent practice in the application of the treaty which establishes the agreement of the parties regarding its interpretation’ (emphasis added). No single act, such as a missile strike, can establish an agreement of the parties. Taken collectively, the responses to the Chinese test reveal that (1) states are concerned about the creation of long-lasting Space debris; (2) some states consider the deliberate creation of long-lasting debris to be illegal; (3) no state, not even China, is willing to assert that the deliberate creation of long-lasting debris is legal.

The response of the United States unfolded over several stages, first in public and then behind closed doors. Immediately after the Chinese test, US National Security Council spokesperson Gordon Johndroe stated, ‘The United States believes China’s development and testing of such weapons is inconsistent with the spirit of cooperation that both countries aspire to in the civil space area. We and other countries have expressed our concern to the Chinese.’Footnote ²⁸

Later, once it became clear just how much debris had been created, the US embassy in Beijing was instructed to make a démarche to the Chinese government based on a set of ‘talking points’ to be left with the Chinese as a ‘non-paper’. For the purposes of this chapter, the relevant talking points listed in this deliberately unofficial document were:

• Debris from China’s ASAT test has increased hazards to other peaceful uses of space in low earth orbit by the United States and other space-faring nations.

• This is a very serious matter for the entire international community.

• Unfettered access to space and the capabilities provided by satellites in orbit are vital to United States national and economic security.

• The United States considers space systems to have the rights of unhindered passage through, and operations in, space without interference.Footnote ²⁹

The last of these talking points shows the United States expressing the view that kinetic ASAT weapon tests impede the freedom of exploration and use of Space when they create long-lasting debris.

Japan came to the same conclusion, with Prime Minister Shinzo Abe stating that the Chinese test violated the Outer Space Treaty, though he did not indicate which specific article had been contravened.Footnote ³⁰ Foreign Minister Taro Aso warned of the danger from debris, saying, ‘I doubt if we could call this a peaceful use.’Footnote ³¹ The European Union also cited the Outer Space Treaty when urging the Chinese to ‘abide by their commitment to exercise their Space activities in accordance with international law’.Footnote ³² Madhavan Nair, the chair of the Indian Space Research Organisation, similarly stated that China ‘should not have done this as it goes against international convention’.Footnote ³³

Other states expressed alarm at the Chinese ASAT weapon test without expressing any specific legal concerns, and these statements, while still relevant, therefore count for less in our legal analysis than the ones above. Australian foreign minister Alexander Downer said his country was ‘concerned about the militarisation of outer space on the one hand and secondly concerned about the impact that debris from destroyed satellites could have on other satellites, which are very expensive pieces of equipment’.Footnote ³⁴ Canada ‘expressed its strong concerns to the Chinese authorities over the reported anti-satellite test and the possible negative effects’.Footnote ³⁵ A spokesperson for the United Kingdom said, ‘We are concerned about the impact of debris in space and we expressed that concern.’Footnote ³⁶

For the purposes of a complete analysis, it should be noted that several states responded to the Chinese ASAT weapon test without addressing the legal or Space debris issues. Russian deputy prime minister Sergei Ivanov stated, ‘The use of outer space for security and defense purposes is one thing, and the placement of weapons there is quite another. The latter is absolutely unacceptable in our view, as it makes the global security situation unpredictable.’Footnote ³⁷ Since the Chinese test was conducted with a ground-based missile, Ivanov’s comment was somewhat off-point. It was, however, soon supplemented by a public acknowledgement of the risks posed by Space debris and knock-on collisions by scientists from the Russian Space Agency, who, in 2009, made a presentation which included the following verbatim text:

China eventually responded to the concerns expressed by other states and did so in a conciliatory manner. Foreign Ministry spokesperson Liu Jianchao said, ‘China consistently advocates peaceful utilization of the outer space, and opposes to weaponization of arms race in the outer space. Neither has China has participated, nor will it participate in arms race of the outer space in any form.’Footnote ³⁹ Some observers believe that the Chinese government had underestimated the negative responses the ASAT weapon test would generate, because of the lack of protests after previous debris-creating tests conducted by the United States and Soviet Union during the 1970s and 1980s.Footnote ⁴⁰ Others believe that the People’s Liberation Army conducted the test without first securing the agreement of the Chinese Foreign Ministry or fully informing the Chinese leadership about the likely creation of large amounts of Space debris.Footnote ⁴¹ Significantly, China did not respond to the concerns of other states by asserting that it had a legal right to test ASAT weapons in an unrestricted manner.

8.1.3 Changes in Practice after the 2007 Chinese ASAT Weapon Test

After the 2007 Chinese ASAT weapon test, which revealed that even a single kinetic weapon can create tens of thousands of pieces of Space debris, subsequent tests were conducted in ways that sought to avoid creating long-lasting debris. In 2008, when the United States employed a missile defence interceptor to destroy a malfunctioning satellite,Footnote ⁴² it did so at a very low altitude.Footnote ⁴³ It also justified its action on the basis that the satellite was about to re-enter the atmosphere with a large amount of highly toxic hydrazine thruster fuel on board.Footnote ⁴⁴ For these reasons, and despite some observers speculating that the US action was a response to the 2007 Chinese test,Footnote ⁴⁵ it did not attract protests from other states.

In 2013, China tested a missile by directing it to ‘nearly geosynchronous orbit’.Footnote ⁴⁶ However, no attempt was made to strike a satellite, in an apparently deliberate effort to avoid creating Space debris. Then, in 2014, China conducted a missile defence test that would have contributed to its ASAT capabilities.Footnote ⁴⁷ However, the missile-to-missile impact took place at a very low altitude.

Since 2007, in China and elsewhere, most ASAT development efforts have focused on highly manoeuvrable spacecraft designed to nudge or pull satellites off course, as well as non-kinetic technologies such as lasers, jammers and cyber actions.Footnote ⁴⁸ None of these methods or technologies contributes directly to the creation of Space debris. However, it is possible that a redirected satellite could incidentally collide with another satellite or with debris, while a satellite subject to a cyber action might be permanently disabled and thus transformed into a substantial piece of long-lived Space debris.

The Space debris crisis is motivating some spacefaring states and companies to include technologies in satellites that allow them to be de-orbited at the end of their operational lives or boosted to sparingly used ‘graveyard’ orbits. ‘Active debris removal’ is also the subject of considerable research. In October 2021, China launched the Shijian-21 spacecraft, which two months later docked with the defunct Beidou-2 G2 navigation satellite in geosynchronous Earth orbit (GEO), about 36,000 kilometres above the equator. In January 2022, Shijian-21 performed an engine burn which raised its altitude – and that of the defunct satellite – by about 3,000 kilometres.Footnote ⁴⁹ Shijian-21 then undocked and returned to GEO, leaving Beidou-2 G2 behind in a very high graveyard orbit. Although the Chinese spacecraft is clearly ‘dual-use’ technology, its employment to remove a defunct satellite from a crowed orbit demonstrates China’s concern about Space debris.Footnote ⁵⁰

The European Space Agency is also testing methods to de-orbit derelict satellites and other Space debris. In 2025, it will launch a spacecraft named ClearSpace-1 equipped with four robotic arms to experimentally capture a piece of debris—a 100-kilogram payload adapter left in an 800 × 660-kilometre orbit following the launch of an ESA remote-sensing satellite in 2013.Footnote ⁵¹ NASA too has similar research projects under way.Footnote ⁵² All of these measures indicate a fast-growing concern about collisions that lead to Space debris, and thus contribute to developing a prohibition on ASAT weapon testing that creates long-lasting debris, as a matter both of treaty reinterpretation and, as we will see later, of customary international law.

8.1.4 Debates and Decisions within Intergovernmental Organisations

Recent debates within intergovernmental organisations demonstrate widespread concern about kinetic ASAT weapon tests that create long-lasting debris as well as growing support for a ban. Some of these statements constitute subsequent practice in support of a reinterpretation of the second paragraph of Article I of the Outer Space Treaty, as well as state practice and evidence of opinio juris for the purposes of customary international law, as discussed below. Decisions taken by intergovernmental organisations can also constitute subsequent practice, as well as state practice and evidence of opinio juris, on the part of their member states, even if the decisions are not themselves legally binding – as with United Nations General Assembly resolutions.Footnote ⁵³ This is particularly the case in the Space context, where all spacefaring states are members of both the General Assembly and the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS). Nearly all of them are also parties to the Outer Space Treaty, which explicitly refers to its parties undertaking Space activities within the framework of international organisations.Footnote ⁵⁴ Finally, decisions taken by international organisations can prompt states to engage in legally relevant subsequent practice beyond the framework of those organisations, with this practice also constituting state practice as well as, perhaps, evidence of opinio juris. An example is a state taking the guidelines adopted by an intergovernmental organisation and making them part of its domestic law.

This is exactly what occurred after COPUOS adopted seven Space Debris Mitigation Guidelines in 2007, including this guideline (their fourth):

Since COPUOS operates on a consensus basis, the guidelines were supported by all of its then 67 member states, which included almost all the spacefaring states (except for Israel, which joined COPUOS in 2015).Footnote ⁵⁶ This support is subsequent practice for the purposes of treaty interpretation (and state practice for the purposes of customary international law). Then, when the UN General Assembly endorsed the Space Debris Mitigation Guidelines later in 2007, it stated that the guidelines themselves ‘reflect the existing practices as developed by a number of national and international organizations’.Footnote ⁵⁷

Now this is where things get interesting: China responded to the Space Debris Mitigation Guidelines by immediately adopting Space debris mitigation requirements for all Chinese entities engaged in Space activities.Footnote ⁵⁸ Then, in 2009, it released domestically binding Interim Measures on Space Debris Mitigation and Protective Management with the aim, according to Yun Zhao, ‘of guaranteeing the normal operation of spacecraft and protection of the Space environment’.Footnote ⁵⁹

Russia introduced its own General Requirements on Space Systems for the Mitigation of Human-Produced Near-Earth Space Pollution in 2008. These requirements, which are binding in Russian domestic law, are explicitly based on the UN Space Debris Mitigation Guidelines.Footnote ⁶⁰

Prior to this, in 1995, NASA was the first Space agency to issue a set of orbital debris mitigation guidelines. Then, in 2001, the binding Orbital Debris Mitigation Standard Practices (ODMSP) became the principal debris-related requirements applicable to all Space activities under the supervision and control of the US government.Footnote ⁶¹ The ODMSP influenced both the subsequent Space debris mitigation guidelines of COPUOS in 2007 and the Inter-Agency Space Debris Coordination Committee (IADC) in 2002.Footnote ⁶² They were updated by the US government in November 2019,Footnote ⁶³ a development that could potentially spur updates to these multilateral guidelines in the years ahead.

Australia’s 2018 Space (Launches and Returns) Act includes as a launch requirement a Space debris mitigation strategy, which must be based on internationally recognised standards or guidelines, such as those of COPUOS and the IADC.Footnote ⁶⁴ Similarly, the Space debris mitigation requirements of Canada’s 2007 Remote Sensing Space Systems Regulations are consistent with both the COPUOS and IADC Space debris mitigation guidelines, with the Canadian Space Agency adopting the latter in 2012 as directly applicable to all its operations.Footnote ⁶⁵

The IADC, noted above, was created even earlier, in 1993, to co-ordinate efforts to deal with orbital debris. It is currently made up of representatives from the European Space Agency and 12 national Space agencies, including those of the United States, Russia, China and India. In 2002, and again (with small revisions) in 2007, 2020 and 2021, the IADC adopted a set of its own Space Debris Mitigation Guidelines.Footnote ⁶⁶ Guideline 5.2.3 on the ‘Avoidance of intentional destruction and other harmful activities’ reads,

The International Organization for Standardization (known as the ISO) is an international non-governmental organisation with 165 members – all of them national standards bodies, some of which are closely connected to governments, others of which are not.Footnote ⁶⁷ In 2010 the ISO adopted a stringent set of Space Debris Mitigation Requirements which apply to all unmanned satellites and spacecraft ‘launched into, or passing through, near-Earth space’.Footnote ⁶⁸ These requirements were updated by the ISO the following year and are ‘intended to reduce the growth of space debris by ensuring that spacecraft and launch vehicle orbital stages are designed, operated and disposed of in a manner that prevents them from generating debris throughout their orbital lifetime’.Footnote ⁶⁹ Among other things, all new satellites must be able to de-orbit to Earth, or boost themselves into graveyard orbits at the end of their lifespan.

The ISO Space Debris Mitigation Requirements are not legally binding. However, in 2015 they were adopted by the European Cooperation for Space Standardization, an initiative, led by the 22 member-state European Space Agency (ESA), that seeks to develop a coherent, single set of user-friendly standards for use in all European Space activities.Footnote ⁷⁰ The standards adopted by the European Cooperation for Space Standardization are applied to all ESA projects,Footnote ⁷¹ a step which constitutes both state practice and perhaps also evidence of opinio juris – not on the banning of kinetic ASAT weapon tests specifically, but rather on the avoidance of debris-creating Space activities in general as legally appropriate behaviour at the global level. In 2019, the ISO released a third edition of its Space Debris Mitigation Requirements,Footnote ⁷² with a fourth edition currently in development.Footnote ⁷³

Making a set of international guidelines binding in domestic law, or within the 22 member-state ESA, is subsequent practice. It is also state practice and, most importantly, evidence of opinio juris, since it suggests that national governments feel an obligation to ensure that the guidelines are followed.

Other debates and decisions within international organisations provide less direct but still significant evidence of a shift in international opinion (although probably not evidence of opinio juris) concerning Space debris and kinetic ASAT weapon testing. For example, in 2012 the UN secretary general established a Group of Governmental Experts on Transparency and Confidence-Building Measures in Outer Space Activities. The group’s consensus report, released the following year, observed that ‘in the context of international peace and security, there is growing concern that threats to vital space capabilities may increase during the next decade as a result of both natural and man-made hazards and the possible development of disruptive and destructive counter-space capabilities’.Footnote ⁷⁴ It then stated, ‘Intentional destruction of any on-orbit spacecraft and launch vehicle orbital stages or other harmful activities that generate long-lived debris should be avoided.’Footnote ⁷⁵

In 2014, the European Union released a draft International Code of Conduct for Outer Space Activities.Footnote ⁷⁶ At its core, the draft code included a set of principles, including ‘the responsibility of states to refrain from the threat or use of force against the territorial integrity or political independence of any state’ and the ‘inherent right of states to individual or collective self-defence’.Footnote ⁷⁷ In this context, the draft code identified that states are required ‘to take all appropriate measures and cooperate in good faith to avoid harmful interference with outer space activities’ and ‘to take all appropriate measures to prevent outer space from becoming an arena of conflict’.Footnote ⁷⁸

In 2019, COPUOS adopted 21 guidelines for the long-term sustainability (LTS) of Space activities.Footnote ⁷⁹ Although the guidelines do not refer specifically to kinetic ASAT weapon testing, they express considerable concern about Space debris, the operational stability of the environment, and the need to ensure that defence and security measures are ‘compatible with preserving outer space for peaceful exploration and use’. They also refer to the 2013 report of the Group of Governmental Experts on Transparency and Confidence-Building Measures in Outer Space Activities, discussed above. For the purposes of our analysis, the LTS guidelines provide yet further evidence that states are changing their practice and views on this issue, thus contributing to the development of a ban on ASAT weapon testing that creates long-lasting debris. We will return to COPUOS shortly when we review the responses of state delegations to another significant 2019 development: the Indian ASAT weapon test.

8.1.5 The Indian ASAT Weapon Test: Conduct and Responses

As mentioned, in 2007 the chair of the Indian Space Research Organisation said that China should not have tested a kinetic ASAT weapon in a manner that created long-lasting debris ‘as it goes against international convention’.Footnote ⁸⁰ Then, in 2012, Vijay Kumar Saraswat, the  scientific adviser to the Indian defence minister, told India Today that the country possessed ASAT technology but ‘[w]e will not do a physical test (actual destruction of a satellite) because of the risk of space debris affecting other satellites.’Footnote ⁸¹ Yet seven years later, on 27 March 2019, India conducted exactly such a kinetic ASAT weapon test against one of its own satellites.Footnote ⁸² The test is relevant to our legal analysis in several respects, beginning with the way it was conducted.

The satellite was struck at an altitude of about 283 kilometres, which according to Indian officials was low enough that the resulting debris would quickly decay and fall back to Earth. In an interview with Reuters, the chair of India’s Defence Research and Development Organisation, G. Satheesh Reddy, asserted that the debris will ‘vanish in no time’ and ‘should be dying down within 45 days’.Footnote ⁸³ He repeated that assurance at a press conference on 6 April 2019, stating that the debris ‘will decay in [a] few weeks’ and ‘won’t cause problem to any existing space assets’.Footnote ⁸⁴ At that same press conference, Reddy explained that the interception was ‘specially designed’ to strike the satellite at an angle so as to ensure ‘minimal debris’.Footnote ⁸⁵ It is possible that these assertions were based, in part, on the perceived results of the 2008 US satellite strike – as discussed above.

As we explained in the previous chapter, the Indian military’s effort to minimise debris did not fully succeed. There are roughly 130 pieces of debris from the test in the USSPACECOM catalogue, meaning that they were in orbit long enough to be tracked and assigned an identifier. It is reasonable to assume that there was at least one order of magnitude more (i.e. 1,300) pieces between one and ten centimetres in size, a size range too small to track but still potentially lethal to satellites, Space stations and astronauts. Some of this long-lived debris, placed on highly eccentric orbits with apogees greater than 1,000 kilometres, remained in Space for over a year (see Figure 7.2 in Chapter 7) – crossing multiple orbital shells twice per orbit.

As with the 2007 Chinese ASAT weapon test, it could be argued that the 2019 Indian ASAT weapon test, as a prominent instance of subsequent practice, confirmed and thus bolstered an interpretation of the Article I, second paragraph, freedom of exploration and use that would allow such testing. But two factors lead to a different conclusion. First, India sought to avoid creating long-lasting debris. As a result, its conduct supports an interpretation of the second paragraph of Article I that prohibits tests that do this. The same conduct concurrently contributes to the development of a parallel rule of customary international law. Second, an examination of the responses to the Indian test confirms that the positions of states on this matter are changing.

8.1.6 Responses to the 2019 Indian ASAT Weapon Test

The Indian ASAT weapon test initially escaped criticism, presumably because of the assurances that no long-lasting debris would result. The United States’ response began with a State Department spokesperson affirming that ‘the issue of space debris is an important concern for the U.S. government. We took note of Indian government statements that the test was designed to address the debris issues’.Footnote ⁸⁶ Then, NASA Administrator James Bridenstine weighed in. He explained that there were 400 identified pieces of trackable debris and 24 of them were in elliptical orbits that extended above the International Space Station,Footnote ⁸⁷ increasing the risk of collisions with the ISS by an estimated 44 per cent.Footnote ⁸⁸ Bridenstine called this ‘a terrible, terrible thing’,Footnote ⁸⁹ and stated that this ‘kind of activity is not compatible with the future of human spaceflight that we need to see happen … It is not acceptable for us to allow people to create debris fields that put at risk our people’.Footnote ⁹⁰ US Defense Secretary Patrick Shanahan was also critical of India’s test: ‘we all live in space, let’s not make it a mess. Space should be a place where we can conduct business. Space is a place where people should have the freedom to operate’.Footnote ⁹¹

The Russian Foreign Ministry issued a press release the day after the test in which it acknowledged India’s peaceful intent but noted that the test was nonetheless the result of a larger deterioration in arms control.Footnote ⁹² It urged India to support the Chinese–Russian draft treaty on Space weapons.Footnote ⁹³ Pakistan, India’s regional rival, expressed ‘grave concern’ about the test and the threat posed by the resulting Space debris to orbital installations such as the ISS.Footnote ⁹⁴

As the Indian ASAT weapon test took place just before the annual session of the Legal Subcommittee of COPUOS in early April 2019, several states expressed concerns during the session about debris-generating ASAT weapon testing. Germany stated,

France said that it is ‘the obligation of states to abstain … [from] the intentional destruction of space objects’.Footnote ⁹⁶ Finland observed, ‘Any unnecessary or voluntary creation or increase of in-orbit space debris population can be viewed … to run counter to the norms and principles of responsible behaviour in outer space.’Footnote ⁹⁷ A delegate from the Netherlands stated,

Canada said, ‘Impacts and collisions involving space debris present a serious challenge to our continued exploration and use of outer space.’Footnote ⁹⁹ Austria commented, ‘The intentional destruction of spacecraft, in contradiction to the abovementioned Space Debris Mitigation Guidelines, may therefore be an indicator of fault when it comes to determining the liability of the launching state for damage caused by space debris created by the intentional destruction.’Footnote ¹⁰⁰ Last but not least, the European Space Agency, which holds observer status within COPUOS, stated, ‘Intentional destructions, which will generate long-lived debris, should not be planned or conducted.’Footnote ¹⁰¹

Collectively, these responses to India’s test constitute subsequent practice for the purposes of a reinterpretation of the second paragraph of Article I of the Outer Space Treaty against ASAT weapon testing that creates long-lasting debris. They also constitute state practice and evidence of opinio juris in support of a developing rule of customary international law, as will be discussed below.

8.1.7 The 2021 Russian ASAT Weapon Test

As we explained in the previous chapter, the Russian military used a ground-based missile to strike Kosmos 1408 on 15 November 2021. It had previously tested the PL-19 Nudol missile’s capabilities as an ASAT weapon through ‘flybys’, i.e. without attempting to strike an actual satellite, thereby demonstrating at least some concern about the creation of long-lasting Space debris.Footnote ¹⁰² No such concern was manifest this time.

The defunct Soviet-era satellite had a mass of about 1,750 kilograms and was orbiting at an altitude of about 480 kilometres. Due to the high impact energies involved in such a strike, debris ended up on highly eccentric orbits that cross the orbital altitudes of thousands of other satellites twice per revolution. Moreover, as the debris de-orbits with time, it will all pass through the altitudes of the International Space Station and China’s new Tiangong Space station. Indeed, shortly after test, the crew members of the ISS – four Americans, one German and two Russians – were woken up by their respective mission controls, told that there had been a ‘satellite break-up’, and asked to close the hatches to the radial modules on the station.Footnote ¹⁰³ The crew members were then directed into their hardened Crew Dragon and Soyuz capsules for two hours as the ISS passed through the debris cloud.

Remarkably, the Russian Defence Ministry denied that debris from the test threatened other satellites. ‘[E]merging fragments at the time of the test and in terms of the orbit’s parameters did not and will not pose any threat to orbital stations, satellites and space activity’, it said.Footnote ¹⁰⁴ It also noted, ‘Earlier, such tests in outer space were already conducted by the United States, China, and India.’

In response, US Secretary of State Anthony Blinken issued a statement that read, in part,Footnote ¹⁰⁵

NASA Administrator Bill Nelson said,

NATO secretary general Jens Stoltenberg said the test was reckless, posed a threat to the ISS and the Chinese Space station, and showed that Russia was developing new weapons systems.Footnote ¹⁰⁷ The North Atlantic Council, made up of representatives from all 30 NATO states, then released the following statement:Footnote ¹⁰⁸

Separate from this, France’s Defence and Foreign Ministries issued a joint statement in which they said the test was ‘destabilising, irresponsible and likely to have consequences for a very long time in the space environment and for all actors in space’.Footnote ¹⁰⁹ In an earlier tweet, French defence minister Florence Parly went so far as to call the Russian military ‘space vandals’ who ‘generate debris that pollutes and puts our astronauts and satellites in danger’.Footnote ¹¹⁰

Josep Borrell, the high representative of the European Union for Foreign Affairs and Security Policy, issued a statement on behalf of all 27 EU Member States that read, in part,Footnote ¹¹¹

Nine non-EU states – North Macedonia, Montenegro, Albania, Iceland, Liechtenstein, Norway, Ukraine, Moldova and Georgia – aligned themselves with this declaration.Footnote ¹¹²

The British defence minister also weighed in, saying that the test ‘shows a complete disregard for the security, safety and sustainability of space. The debris resulting from this test will remain in orbit putting satellites and human spaceflight at risk for years to come’.Footnote ¹¹³ A joint media release from the Australian defence and foreign ministers described the Russian test as ‘a provocative and dangerous act that demonstrated the threats to space systems are real, serious and growing’.Footnote ¹¹⁴ The German foreign minister was equally critical:

In Japan, the Ministry of Foreign Affairs issued a statement that read, in part,Footnote ¹¹⁶

In South Korea, the Foreign Ministry sent a text message to reporters that read, ‘We are concerned about the anti-satellite weapon test that took place Nov. 15 and in particular numerous pieces of debris created in space as a result of the test.’Footnote ¹¹⁷ In the same message, it urged ‘all nations to act responsibly in space to ensure peaceful and sustainable use of space, and work together to advance related international rules’.

Then, there was China. When asked about the Russian test during a press conference the following day, Foreign Ministry spokesperson Zhao Lijian said, ‘We noted relevant reports and that Russia has yet to respond. I think it is too early to make any comment.’Footnote ¹¹⁸ Two months later, a report from the Chinese state-controlled Global Times – widely regarded as a mouthpiece for the government – signalled that China was very concerned about Russia’s action, not least after a close conjunction between one of its scientific satellites and a piece of debris from the test. A long excerpt from that report is reproduced here, because of its considerable importance:Footnote ¹¹⁹

This report from Global Times and the responses summarised above demonstrate that Russia’s 2021 ASAT weapon test generated considerable concern among other states, including all the other major spacefaring states. Indeed, as Nivedita Raju observed, ‘India’s destructive ASAT test in March 2019 generated fewer and much softer responses than Russia’s.’Footnote ¹²⁰ Many of the responses to the Russian test will constitute subsequent practice for the purposes of interpreting the second paragraph of Article I of the Outer Space Treaty, as well as state practice and evidence of opinio juris for the purposes of customary international law. Just as importantly, not a single state responded to the Russian ASAT weapon test by saying that it was an appropriate or internationally legal action.

In terms of international law-making, it is especially significant that Russia denied that the ASAT weapon test created risks for operational satellites or Space stations. As we demonstrated in the previous chapter, the denial was scientifically implausible. Yet it also constitutes a clear, if implicit, acknowledgement, by the Russia government, that the deliberate creation of dangerous debris is unacceptable today. The denial was, in short, more legally relevant than the test itself as subsequent practice for the purpose of interpreting the second paragraph of Article I, and as state practice and evidence of opinio juris for customary international law.

As we explained in the previous chapter, the prohibition on torture (a rule found in numerous treaties as well as customary international law) provides a powerful example of how denials of actions can contribute to those actions being, or becoming, illegal. To quote Anthony D’Amato again:

D’Amato went on to explain that ‘hiding, cover-up, minimization, and non-justification … betoken a violation of law’ and therefore constitute legally relevant state practice in support of a rule prohibiting the actions in question.Footnote ¹²² Russia, by denying that it created dangerous debris in November 2021, was strengthening, not weakening, a possible new rule against testing ASAT weapons in ways that create long-lasting debris.

8.1.8 United Nations General Assembly Resolutions 75/36 and 76/231

In December 2020, the United Nations General Assembly adopted Resolution 75/36 on Reducing Space Threats through Norms, Rules and Principles of Responsible Behaviours.Footnote ¹²³ The resolution:

The resolution further requested that the UN secretary general ‘seek the views of Member States’. Those views, compiled in a report to the General Assembly at its 76th session in September 2021, show strong support for restrictions on kinetic ASAT weapon testing.Footnote ¹²⁴

Russia called for ‘a complete and comprehensive ban on space-based strike weapons as well as on any land-, air-, or sea-based systems designed to destroy objects in outer space’. China expressed a similar view. Australia, Canada, France, Germany, Italy, Japan, Luxembourg, the Netherlands, Norway, Slovenia, the United Kingdom and the European Union all expressed the view that kinetic ASAT weapon tests should be avoided. Ireland, New Zealand and the United States identified kinetic ASAT weapon tests as a category of behaviour ‘that could be considered during further development and implementation of norms, rules, and principles of responsible behaviours’. Brazil, Mexico, Sweden and Switzerland expressed support for multilateral negotiations leading to legally binding constraints on kinetic ASAT weapon testing.Footnote ¹²⁵ Most importantly, not a single state in its response submitted for this United Nations report considered the testing of kinetic ASAT weapons to be an appropriate or internationally legal action.

Then, in December 2021, the United Nations General Assembly adopted Resolution 76/231,Footnote ¹²⁶ which created an open-ended working group:

It is possible that the open-ended working group will negotiate a draft treaty banning kinetic ASAT weapon testing, as recommended in an international open letter co-ordinated by the Outer Space Institute in September of that year.Footnote ¹²⁷ That letter, signed by former prime ministers, Nobel laureates, retired astronauts and hundreds of other experts, was addressed to the president of the General Assembly.

The open-ended working group did not, however, experience a smooth launch. At their first organisational meeting, in early February 2022, the members of the group decided to postpone the first substantive session from mid-February to May. According to a report from Breaking Defense, ‘Russia raised a litany of procedural complaints’, arguing that national delegations needed more time to prepare and seeking ‘new limitations preventing representatives of non-governmental organizations (NGOs) from speaking or providing direct input’. The author of the report, the well-informed Theresa Hitchens, added some extra colour when she explained that the latter issue ‘was left unresolved when the formal meeting adjourned to a private venue, after the clock ran out on interpretation services at the Palais de[s] Nations and building management threatened to kill the lights on the diplomatic squabbling’.Footnote ¹²⁸

It is important to note that early February 2022 was a time of newly heightened tension between Russia and Western states, with missiles, tanks and nearly 200,000 Russian troops massed on Ukraine’s borders. Aidan Liddle, the British ambassador to the Conference on Disarmament in Geneva, took to Twitter to express a more optimistic view of the squabbling within the working group. ‘[T]hat’s the nature of multilateral diplomacy’, he wrote. ‘[A]nd when it works, it’s worth the wait’.Footnote ¹²⁹ Russia’s subsequent invasion of Ukraine on February 24 and the corresponding near breakdown in relations with Western states simultaneously make the new working group even more relevant, while creating major uncertainty for its future.Footnote ¹³⁰

8.1.9 The 2022 United States ‘Unilateral Declaration’

Something quite unusual happened on 18 April 2022 when, during a speech at Vandenberg Space Force Base in California, US Vice President Kamala Harris solemnly declared that ‘as of today, the United States commits not to conduct destructive direct ascent anti-satellite missile testing’.Footnote ¹³¹ In international law, statements such as these are called ‘unilateral declarations’ and are legally binding.

In the 1974 Nuclear Tests Cases, the International Court of Justice wrote,

The unilateral declaration at issue in the Nuclear Tests Cases was a commitment not to test nuclear weapons in the atmosphere, made publicly by both the French president and the French foreign minister. The parallel with Vice President Harris’s declaration, which also involves weapons testing in an ‘area beyond national jurisdiction’, is striking.

In 2006, the United Nations International Law Commission (ILC) completed a decade-long study on unilateral declarations and issued a set of ten Guiding Principles. These principles confirmed that a unilateral declaration, if made publicly, in clear and specific terms, and by an authority vested with the power to do so, constitutes a binding commitment vis-à-vis all other states.Footnote ¹³³ Those states ‘may then take them into consideration and rely on them; such States are entitled to require that such obligations be respected’.Footnote ¹³⁴ The ILC also confirmed that a unilateral declaration ‘cannot be revoked arbitrarily’, with arbitrariness being determined, in part, by ‘the extent to which those to whom the obligations are owed have relied on such obligations’.Footnote ¹³⁵

It is therefore clear that the United States is now bound, under international law, not to engage in direct-ascent ASAT missile tests. Importantly, other states may now rely on the US commitment, for instance, while deciding not to develop or test ground-based kinetic ASAT weapons themselves.

At the same time, it is important to note that the US unilateral declaration does not extend to, and therefore does not commit the United States to avoid, the testing of Space-based kinetic ASAT weapons or the testing of non-kinetic technologies such as lasers, jammers or cyber attacks, whether destructive or not. We also note that the United States already possesses the capability that it has committed not to test, as demonstrated by the use of a ship-based missile in 2008 to destroy a malfunctioning satellite. Nor does the unilateral declaration extend to the testing of missile defence interceptors, which are effectively dual-use ASAT weapons and, as demonstrated in the previous chapter, capable of generating long-lasting Space debris. But while the US unilateral declaration is tightly focused, this is not necessarily a bad thing, since it should make it easier for other states to follow suit, either by making their own declarations, or by refraining from testing such weapons themselves, or both.

The intent of the US government to create momentum and persuade others to make similar unilateral declarations is clear. As Vice President Harris said in the same speech,

Canada, New Zealand, Japan, Germany, South Korea, the UK, and Australia soon made similar declarations. Now, a series of unilateral declarations cannot in themselves make a ‘new international norm’ that binds all states, but they can contribute to generally applicable rules in two ways. First, they count as ‘subsequent practice’ for the purposes of interpretating the second paragraph of Article I of the Outer Space Treaty, and specifically the ‘freedom of exploration and use of space’, in a manner that precludes kinetic ASAT weapon tests that create long-lasting debris. Second, they can contribute to the development of customary international law as both state practice and expressions of opinio juris.

8.4.1 Armed Attack

A military vessel is treated as an extension of a state’s territory; as a result, the use of force against such a vessel generally constitutes an ‘armed attack’ giving rise to a right of self-defence.Footnote ¹⁶⁵ The use of force against a military satellite, therefore, should have the same consequence, subject to several contextual factors.Footnote ¹⁶⁶ Whether any particular use of force constitutes an armed attack will, for example, depend upon its gravity. As the International Court of Justice held in the Nicaragua Case, ‘It is necessary to distinguish the most grave forms of the use of force (those constituting an armed attack) from other less grave forms.’Footnote ¹⁶⁷

This threshold for an armed attack is needed to help prevent small incidents from escalating into large conflicts, since the state being attacked may (if it respects the criteria of necessity and proportionality, as discussed below) respond to an armed attack by using force against elements of the attacking state’s military that were not used in the initial attack. To illustrate the point, consider what happens when a missile system on a military vessel from one state ‘locks on’ to a military aircraft from another state. Although the act of locking on is considered to demonstrate hostile intent and could well constitute a violation of Article 2(4) as a threat to use force, it would not normally constitute an armed attack because the gravity threshold will not have been reached. As a result, the state subject to the locking on will not be entitled to use force in response, either against the military vessel or against additional elements of the other state’s armed forces. It may, however, be entitled to engage in non-forceful ‘countermeasures’ (i.e. measures that would otherwise be contrary to international law, but which are permitted if taken in response to an internationally wrongful act in order ‘to procure cessation and reparation’).Footnote ¹⁶⁸

Border incursions, where a small number of troops briefly cross into the territory of another state, are treated in a similar manner. In the Nicaragua Case, the Court explained that ‘scale and effects’ are what distinguish an armed attack from a ‘mere frontier incident’.Footnote ¹⁶⁹ The gravity requirement was reaffirmed in the subsequent Oil Platforms Case, where the Court held that Iran’s deployment of a mine without the specific intent to damage a US military vessel was insufficiently grave to constitute an armed attack.Footnote ¹⁷⁰

Now consider how the gravity requirement might apply to actions taken against a foreign military satellite in peacetime. What if the satellite were only temporarily disabled by dazzling or jamming? Or what if the satellite were destroyed by a missile but there was no direct loss of life or significant damage to assets or people on the ground? At first glance, neither situation would reach the gravity threshold for an ‘armed attack’ and thus trigger the right of self-defence. However, it is unlikely that any use of a kinetic ASAT weapon against a military satellite would be directed solely at the machinery of the satellite. It would, most likely, also be directed at degrading the situational awareness, communications and control of armed forces on the ground – in other words, core military capabilities made possible by the satellite. Since the use of kinetic ASAT weapons against military satellites would almost always be directed at these core capabilities, the scale and effects of their use would almost always reach the gravity threshold and constitute an armed attack.

The same logic – focusing on the scale and effects of the strike on military capabilities, rather than on the satellite itself – could lead to the conclusion that strikes against dual-use satellites might also constitute armed attacks, even if the satellites are owned by private companies. That said, some dual-use satellites might only provide occasional service to military customers. The fact that a satellite is dual-use will not determine whether a strike against it constitutes an armed attack. What matters is the scale and effects of the use of force in terms of its impact on the targeted satellite’s contributions to a state’s military activities.

The analysis becomes even more difficult with purely civilian satellites that form no part of a state’s military apparatus, but in many cases constitute key economic infrastructure or serve as tools for search and rescue and disaster relief. International law has addressed this issue in the past, albeit in the context of oceans rather than Space: a military action against a single civilian vessel will not usually constitute an armed attack, but a military action against an entire merchant fleet could.Footnote ¹⁷¹ Similarly, cyber actions against civilian computers can constitute an armed attack, but only if they cause significant economic damage or imperil essential state functions such as power grids, hospitals or air traffic control.Footnote ¹⁷² Applying the same logic to civilian satellites, an action that causes economic damage or imperils essential functions could be considered an armed attack, provided the scale and effects are serious enough.Footnote ¹⁷³

This conclusion raises further, highly context-dependent issues of redundancy and resilience, since some states are better able than others to withstand the loss of one satellite or a small number of them. Does a state with many civilian satellites have a higher threshold for suffering an armed attack, given that any satellites that are not targeted could continue providing economic and essential services? The answer would seem to be yes, though it is impossible to identify the exact number or percentage of satellites that would need to be lost before a right of self-defence would arise. Each situation will have to be assessed on its own terms, and again, a consideration of scale and effects will be determinative. It is clear, however, that militaries developing satellite constellations to provide redundancy for security purposes are reducing the chances of the threshold of ‘armed attack’ being achieved. Satellite constellations might thus help to prevent escalations for any single attack. Attacks designed to disable entire constellations, though, will need to be considered differently.

Even if a particular use of an ASAT weapon against a satellite constitutes an ‘armed attack’ and thus triggers a right of self-defence, this does not give the attacked state carte blanche in its response. The right of self-defence includes the criteria of necessity and proportionality, which limit the type and scale of any permissible reaction.

8.4.2 Necessity and Proportionality

As the International Court of Justice held in the Nicaragua Case, ‘whether the response to the [armed] attack is lawful depends on observance of the criteria of the necessity and the proportionality of the measures taken in self-defence’.Footnote ¹⁷⁴ Applying these criteria – essentially balancing the reasons for taking military action against its negative impacts on other states as well as civilians – is always a fact-specific exercise. For this reason, as Christine Gray explains, ‘There was until recently relatively little general academic discussion of these essential characteristics of self-defence, as opposed to discussion in application to particular incidents.’Footnote ¹⁷⁵ It is possible, however, to make two general observations about the application of necessity and proportionality to ASAT weapons that lead to specific conclusions.

First, when it comes to necessity and proportionality applied to ASAT weapons, the armed attack and the response might well occur in different domains. It is possible that both the armed attack and the response will occur in Space. For instance, a satellite operated by one state might be used to attack a satellite operated by another state, and in response the state that has been attacked destroys either the attacking satellite (if it was not initially destroyed) or another satellite operated by the aggressor state. Alternatively, it is also possible that the state that has been attacked in Space will engage in a ‘cross-domain’ response directed at targets on Earth, such as a satellite ground station belonging to the aggressor state. However, the most likely scenario is that the armed attack will occur on Earth and the responding state will engage in a cross-domain response in Space, targeting one or more satellites to interrupt the aggressor state’s situational awareness, communications and control. As we will see below, factors specific to one domain, such as Space debris, can influence the application of the criteria of necessity and proportionality in ways that do not occur in another domain.

Second, it is not easy to apply the criteria of necessity and proportionality in the context of ASAT weapons. One might, for example, see an analogy between military and dual-use satellites, on the one hand, and remotely-controlled communications towers and radar facilities, on the other, in that taking military action against a satellite could not only disable a potential adversary’s situational awareness, communications and control, but also do so without causing direct casualties. However, the analogy does not hold, because military and dual-use satellites have distinctive attributes.

8.5.1 Military Necessity

The principle of military necessity is central to the jus in bello. In the words of Article 52(2) of Additional Protocol I to the Geneva Conventions, belligerents may lawfully target ‘those objects which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage’.Footnote ¹⁸⁸ Military satellites could well qualify as such objects under this legal definition. So too might some dual-use satellites, if they are being employed by an adversary for military purposes including communications, situational awareness or targeting.

8.5.2 Distinction

The principle of distinction is also central to the jus in bello, with Additional Protocol I prohibiting indiscriminate attacks, including those that ‘employ a method or means of combat which cannot be directed at a specific military objective’Footnote ¹⁸⁹ or ‘may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated’.Footnote ¹⁹⁰

As Bill Boothby explains,

Boothby concludes that ASAT weapons ‘that are likely to cause debris clouds in areas of outer space that civilian satellites may be expected to use are likely to be regarded as breaching the indiscriminate attacks rule’.Footnote ¹⁹² We further note, as discussed in the previous chapter, that a fragmentation event at one orbital altitude will affect a broad range of altitudes, such that it is infeasible to distinguish military orbital Space from civilian orbital Space. Indeed, such a distinction does not exist.

8.5.3 Proportionality

A third core principle of the jus in bello is proportionality – between military advantage on the one hand and the protection of civilians and civilian objects on the other. This long-standing rule of customary international law also finds expression in Additional Protocol I, with Article 57(2)(a) stipulating that ‘those who plan or decide upon an attack shall’:

1. (ii) take all feasible precautions in the choice of means and methods of attack with a view to avoiding, and in any event to minimizing, incidental loss of civilian life, injury to civilians and damage to civilian objects;

2. (iii) refrain from deciding to launch any attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated.

Today, the principle of proportionality must be applied to ASAT weapons within the context of an increasingly busy orbital environment, Space debris and the risk of knock-on collisions, as well as the severe consequences for civilians that would result from the loss of essential satellite services. We can only conclude that the use of an ASAT weapon in a manner that creates long-lasting Space debris would be disproportionate and therefore illegal under the jus in bello.

Sometimes, the principle of proportionality can require states to choose different kinds of weapons, or different targets. APV Rogers provides an example of proportionality at work in the planning of a US airstrike on a hydroelectric dam during the Vietnam War:

In other words, the principle of proportionality required the United States to choose a different kind of weapon to reduce the risk of civilian harm. Michael Schmitt has explained how the same rebalancing might operate in the context of ASATs:

As for the choice of targets, the awkwardly worded Article 57(3) of Additional Protocol I states, ‘When a choice is possible between several military objectives for obtaining a similar military advantage, the objective to be selected shall be that the attack on which may be expected to cause the least danger to civilian lives and to civilian objects.’ On this, Schmitt writes,

Again, the principle of proportionality could rule out the use of ASAT weapons involving violent impacts, and push states towards other types of weapons and other types of targets.

For all these reasons, we agree with the International Committee of the Red Cross. In 2021, the ICRC submitted a position paper to the secretary general of the United Nations in which it wrote, ‘When assessing the lawfulness of such [ASAT weapon] attacks, all foreseeable direct and indirect incidental harm or damage to civilian objects must be considered, including when targeting a dual-use space object. The risk of creating debris and its indirect effects … should also be considered when applying these rules.’Footnote ¹⁹⁶

It is difficult to imagine circumstances where a kinetic ASAT weapon could be used without violating the jus in bello, which, again, is often referred to as international humanitarian law.