Is jus in bello applicable in space?
For reference only
NOTE: This is an essay submitted for an assignment on international, environmental and space law. The page is for reference only, as my peers and I have already received our marks for the assignment.
This assignment has been assessed and falls in the 85-100 per cent range where marking is based on:
the knowledge and understanding of the concepts and principles of the international legal system, and its relevance to the governance of outer space
the skill to:
interpret and apply legal principles and authorities to evaluate relevant law in the context of the question
demonstrate independent research skills, and
present and structure information clearly and accurately using language appropriate for the intended audience with appropriate citation and referencing of relevant sources
This essay critically analyses the following statement in relation to the applicability and suitability of the rules of jus in bello to outer space:
War in space is unimaginable as states have committed to the peaceful uses of outer space. Consequently, the rules of jus in bello (rules that govern the way in which warfare is conducted) which are part of International Humanitarian Law, should not apply to outer space, as that would only encourage states to create weapon systems for combat in space. Moreover, given the profound difference of the space and terrestrial environments, it would be impossible to apply the principles of jus in bello to outer space.
The essay “leaves very little scope for improvement” and the “only suggestion” is to “continue monitoring the very latest developments in this fast-evolving area of space law and military operations, to ensure your arguments remain fully up to date.”
In this version below, the referencing format is changed to streamline everything into a footnote list—as opposed to footnotes for legal sources and reference list for general academic sources. The first mention of primary sources (case laws, legistlations, etc.) are also hyperlinked to give you direct access to them.
The question statement posits that the commitment to peaceful uses of outer space renders war unimaginable. Consequently, jus in bello, should not apply as it would encourage weaponisation. Jus in bello, a cornerstone of international humanitarian law (IHL), regulates the conduct of hostilities with the aim of minimising suffering and protecting non-combatants. It further argues that the environmental differences between space and Earth make the application of jus in bello impossible. This perspective, while reflecting a desirable ideal for outer space, necessitates a critical examination against the established principles of international law, the realities of state practice, and the specific provisions of space law.
The first assertion hinges on the concept of outer space being reserved for peaceful purposes, suggesting that any military activity, including armed conflict and the application of jus in bello, is incompatible with this fundamental principle. Indeed, the Preamble to the Outer Space Treaty (OST)1 references the “common interest of all mankind in the progress of the exploration and use of outer space for peaceful purposes.” Article IV of the OST includes a “peaceful purposes” concept,2 and the Moon Agreement3 prohibits the threat or use of force on celestial bodies, their orbits, and trajectories. Some early interpretations, particularly from Soviet publicists, viewed “peaceful” as synonymous with “non-military,” advocating for a prohibition of all military activities in space (Bourbonniere and Lee, 2007, p. 876;4 Goh, 2004, p. 269).5 This perspective would lend support to the statement’s argument that jus in bello, governing hostilities, should not apply because such activities are inherently non-peaceful and thus impermissible in space.
However, a critical analysis of state practice reveals a more nuanced understanding of the “peaceful purposes” principle, which others interpret to mean “non-aggression purposes” (Bourbonniere and Lee, 2007, p. 876; Goh, 2004, p. 269). It is supported by the consistent state practice of deploying military or dual-use satellites, for example, for communications and remote sensing in orbit around the Earth (The Open University (OU), 2025a, 7.4).6 These are activities that are military in nature but not typically considered aggressive (Mawdsley, 2020, p. 283).7 Further, Article IV of the OST8 prohibits the placement of nuclear weapons and weapons of mass destruction in orbit, and the establishment of military bases, installations, fortifications, weapons testing, and military manoeuvres on celestial bodies. Nonetheless, the presence of these specific prohibitions, while significant, implies that other military activities in space are not entirely banned by the treaty (Vermeer, 2007, p. 334).9 Additionally, the United States of America, China, India, and Russia have all demonstrated capabilities to disrupt or destroy satellites, highlighting the potential for space-based conflict (OU, 2025b, 6).10 Subsequently, this has led to calls to ban anti-satellite weapons (Cheney, 2021, cited in OU, 2025c, 6.2.3.).11 This broader discussions suggest the aspiration for peaceful uses does not completely preclude military activities, thereby weakening the claim that war in space is “unimaginable,” and undermines the argument that jus in bello is inapplicable.
A more fundamental point challenging the statement is the broadly accepted notion that general international law applies to activities in outer space. This effectively extends rules and principles of international law to space, including jus in bello. For example, Article III of the OST12 explicitly provides that states shall conduct activities in space in accordance with international law, including the Charter of the United Nations. The UN General Assembly also consistently reaffirms the applicability of the UN Charter and general international law to outer space activities (O’Meara, 2025, p. 7).13 Additionally, state practices, including recent declarations from major space powers and international organisations such as the U.S., NATO, and the European Union, demonstrate a commitment to conducting space activities in accordance with international law (O’Meara, 2025, p. 7). Mačák (2018, p. 34)14 argues that this means that, despite the aspirations for peace, state and international bodies acknowledge that if an armed conflict extends into or originates from space, the rules governing the conduct of that conflict are applicable by virtue of this existing legal framework.
The original statement’s concern that applying jus in bello to space would encourage weaponisation is also open to criticism. Jus in bello governs the conduct of hostilities during an armed conflict (OU, 2025d, 7).15 Its primary purpose is to regulate the means and methods of warfare and protect persons and objects not participating in hostilities, thereby limiting the suffering caused by conflict. However, as Mačák (2018, p. 37) notes, the regulation of a particular form of conduct by law does not, in itself, confer legitimacy upon said conduct. On the contrary, jus in bello imposes restrictions designed to constrain the behaviour of belligerents in warfare. Applying rules to regulate combat in outer space does not make resorting to that combat lawful, which is a matter for jus ad bellum, the law governing the resort to force (OU, 2025d, 7). Therefore, the application of jus in bello does not encourage the initiation of conflict or weaponisation, rather, it provides a necessary legal framework to mitigate its effects should it occur, acting as a restraint on belligerent actions.
Nonetheless, the original statement raises a valid point about the challenges posed by the unique nature of the space environment, arguing that this makes application “impossible.” Vermeer (2007, p. 322) and Mačák (2018, p. 4) acknowledge that the uniqueness of space means that customary principles may not be sufficiently specific or appropriate. Orbital mechanics, for example, make applying principles like avoiding civilian satellites problematic due to the vast and complex movements of objects (Tronchetti, 2014, p. 104),16 while defining protected zones in space is also difficult (Bourbonniere and Lee, 2007, p. 899). However, there are hints of an alternative path for separate regimes for various elements of space. For example, while the OST treats outer space, the Moon, and other celestial bodies as one domain, where military activities are concerned, Article IV distinguishes between Earth orbit and the Moon, and other celestial bodies (OU, 2025e, 7.1).17 These practical challenges mean that a direct application of rules developed primarily for terrestrial warfare is not so straightforward and may require some refinement.
Regardless, the existence of challenges does not equate to impossibility. Legal precedents exist for extending IHL to new domains. For example, the UN Group of Governmental Experts of Advancing Responsible State Behaviour in Cyberspace confirms the application of IHL to cyber space, a domain for both civilian and military activities that only came into existence in the mid-twentieth century (Steer, 2023).18 Additionally, in a landmark case, the International Court of Justice, in an advisory opinion on nuclear weapons, which also emerged after the formulations of IHL rules, states that IHL applies to “all forms of warfare and to all kinds of weapons, those of the past, those of the present and those of the future.”19 Thus, jus in bello could evolve to encompass outer space. Concepts such as distinction between military and civilian objects, and proportionality to ensure civilian harm is not excessive, are core to IHL (OU, 2025b, 7). Dual-use satellites, serving both military and civilian purposes, complicates the application of the principle of distinction (van de Put and Siemensma, 2024, p. 36).20 Furthermore, the potential for kinetic attacks to create space debris that threatens civilian and third-party satellites introduces complex proportionality assessments (OU, 2025d, 6). Despite that, IHL principles can be applied. For instance, attacks against military objectives must be terminated if it becomes apparent the target is civilian or the attack would violate proportionality, under Additional Protocol (I) to the Geneva Conventions.21 IHL also requires military objects to bear markings to facilitate identification (Bourbonniere and Lee, 2007, p. 894). Even though there are permissible methods to mislead an enemy by feigning non-combatant status, there are restrictions to it. If found to be a grave violation of IHL, it is a punishable breach under AP(I).22 These considerations indicate a commitment to finding ways to apply the law rather than abandoning it.
The interaction between space law and jus in bello is increasingly viewed not as conflicting but as a relationship requiring “systematic integration” (van de Put and Siemensma, 2024). The international legal framework for space weapons involves international space law, the UN Charter, and IHL, and the interface is crucial. While tensions may arise, for instance, regarding the status of astronauts who also hold combatant status, these can be resolved by considering the context and purpose of the relevant rules. In this example, during peacetime, states are obliged to return astronauts under the Rescue Agreement,23 as they would with shipwrecks in high seas (van de Put and Siemensma, 2024, p. 55). In times of conflict, van de Put and Siemensma (2024, pp. 55-56) propose the treatment of combatant-astronauts to be akin to that of a prisoner of war, which is not punitive, but preventative, as they could no longer participate in hostility, aligned with IHL. Space law, with its focus on protecting the space environment and ensuring freedom of exploration, interacts with IHL, which balances military necessity and humanity. This integrated approach allows for the specific nature of the space domain to be considered within the broader framework of the law of armed conflict, ensuring that fundamental principles are upheld while adapting to the unique environment.
Finally, the original statement’s position contrasts with emerging state practice and the views of key international actors. While the legal implications of space warfare remain under deliberation, there is broad consensus that jus in bello is applicable. Contemporary statements from state agencies and humanitarian organisations such as the U.S. Department of Defense (2015, p. 955),24 the German Navy (2002),25 and the International Committee of the Red Cross (2021)26 affirm that the law of armed conflict applies to hostilities regardless of location, including outer space (van Loon, 2021, pp. 11-12).27 O’Meara (2025, p. 6) and van Loon (2021, p. 14) also point out that efforts are underway to clarify the rules through initiatives such as the Woomera Manual on the International Law of Military Space Activities and Operations and the Manual on International Law Applicable to Military Uses of Outer Space. Although challenges in application persist, the international community appears to move towards accepting and interpreting existing jus in bello principles to address the unique context of space, rather than denying their applicability. This trend suggests that jus in bello is indeed applicable and relevant to outer space.
While the unique nature of outer space poses challenges to the application of jus in bello, it does not preclude it. As military capabilities expand into space, the IHL principles of distinction, proportionality, necessity, and humanity remain crucial to safeguarding civilian interests and preserving the commitment to the peaceful use of space. The argument that jus in bello would incentivise conflict overlooks the fundamental function of IHL, which is to impose humanitarian standards on warfare, irrespective of the domain.
Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space 1967 Art IV
Bourbonniere, M. and Lee, R.J. (2007) ‘Legality of the deployment of conventional weapons in Earth orbit: Balancing space law and the law of armed conflict’, European Journal of International Law, 18(5), pp. 873-901. Available at: https://doi.org/10.1093/ejil/chm051 (Accessed: 4 May 2025).
Goh, G.M. (2004) ‘Keeping the peace in outer space: A legal framework for the prohibition of the use of force’, Space Policy, 20(4), pp. 259-278. Available at: https://doi.org/10.1016/j.spacepol.2004.08.002 (Accessed: 4 May 2025).
The Open University (2025a) ‘Unit 6: The governance of outer space’. W260 International, environmental, and space law. Available at: https://learn2.open.ac.uk/mod/oucontent/view.php?id=2398335§ion=7.4 (Accessed: 4 May 2025).
Mawdsley, J. (2020) ‘Applying core principles of international humanitarian law to military operations in space’, Conflict & Security Law, 25 (2), pp. 263-290. Available at: https://doi.org/10.1093/jcsl/kraa005 (Accessed: 5 May 2025).
Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space 1967 Art IV
Vermeer. A. (2007) ‘A legal exploration of force application in outer space’, Military Law and Law of War Review, 46(2), pp. 299-340. Available at: https://heinonline.org/HOL/P?h=hein.journals/mllwr46&i=299 (Accessed: 4 May 2025).
The Open University (2025b) ‘Unit 7: Planetary protection and astroenvironmentalism’. W260 International, environmental, and space law. Available at: https://learn2.open.ac.uk/mod/oucontent/view.php?id=2398337§ion=6 (Accessed: 4 May 2025).
The Open University (2025c) ‘Unit 7: Planetary protection and astroenvironmentalism’. W260 International, environmental, and space law. Available at: https://learn2.open.ac.uk/mod/oucontent/view.php?id=2398337§ion=6.2.3 (Accessed: 4 May 2025).
Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space 1967 Art III
O’Meara, C. (2025) ‘Self-defence in outer space: Anti-satellite weapons and the jus ad bellum’, Leiden Journal of International Law, pp. 1-23. Available at: https://doi.org/10.1017/S0922156524000670 (Accessed: 4 May 2025).
Mačák, K. (2018) ‘Silent war: Applicability of the jus in bello to military space operations’, International Law Studies, 94, pp. 1-38. Available at: https://digital-commons.usnwc.edu/cgi/viewcontent.cgi?article=1717&context=ils (Accessed: 4 May 2025).
The Open University (2025d) ‘Unit 6: W260 International, environmental, and space law. Available at: https://learn2.open.ac.uk/mod/oucontent/view.php?id=2398335§ion=7 (Accessed: 4 May 2025).
Tronchetti, F. (2014) ‘The right of self-defence in outer space: An appraisal’, Zeitschrift fur Luft- und Weltraumrecht German Journal of Air and Space Law, 63(1), pp. 92-120. Available at: https://heinonline.org/HOL/P?h=hein.journals/zlw63&i=96 (Accessed: 4 May 2025).
The Open University (2025e) ‘Unit 7: Planetary protection and astroenvironmentalism’. W260 International, environmental, and space law. Available at: https://learn2.open.ac.uk/mod/oucontent/view.php?id=2398337§ion=7.1 (Accessed: 4 May 2025).
Steer, C. (2023) ‘International humanitarian law in the “grey zone” of space and cyber’. Available at: https://www.cigionline.org/articles/international-humanitarian-law-in-the-grey-zone-of-space-and-cyber/ (Accessed: 18 May 2025).
van de Put, S. and Siemensma, A.E. (2024) ‘A giant leap for humankind: Bridging space and international humanitarian law’, The Military Law and Law of War Review, 62(1), pp. 31-57. Available at: https://doi.org/10.4337/mllwr.2024.01.02 (Accessed: 4 May 2025).
Additional Protocol (I) to the Geneva Conventions 1977, Art. 85(5)
U.S. Department of Defense (2015) Law of War Manual. Available at: https://media.defense.gov/2023/Jul/31/2003271432/-1/-1/0/DOD-LAW-OF-WAR-MANUAL-JUNE-2015-UPDATED-JULY%202023.PDF (Accessed: 10 May 2025).
German Navy (2002) Commander’s Handbook: Legal bases for the operations of Naval Forces. Available at: https://usnwc.libguides.com/ld.php?content_id=66281931 (Accessed: 10 May 2025).
International Committee of the Red Cross (2021) ‘The potential human cost of the use of weapons in outer space and the protection afforded by international humanitarian law’. Available at: https://www.icrc.org/sites/default/files/document/file_list/icrc_potential_human_cost_of_use_of_weapons_in_outer_space_and_ihl_protection.pdf (Accessed: 17 May 2025).
van Loon, F. (2021) ‘Codifying jus in bello spatialis – the space law of tomorrow’, Strategic Studies Quarterly, 15(1), pp. 10-27. Available at: https://www.jstor.org/stable/pdf/26984766 (Accessed: 4 May 2025).