By Sören Sommer
[Sören Sommer (LL.M.) is a PhD law student at the University of Glasgow.]
The recent Russian anti-satellite missile test has abruptly brought the risk of potential future conflicts in outer space back on the international space and security agenda. As has been repeated time and time again, outer space is increasingly becoming more competitive, congested, contested, and even weaponised (Schrogl et al., 2015, pp. 521-716; Steer, 2017, p. 9). Due to the ever-increasing reliance of modern societies and modern militaries on space assets, sophisticated means and methods of space warfare to use force against space objects are being rapidly developed. Potential future conflicts over space resources and geopolitical conflicts on Earth which might spill-over to space contribute to the fragility of the continued peaceful and cooperative use of outer space and further increase the risk that space objects will be targeted in future outer space conflicts. This entails grave humanitarian consequences due to the potential outage of essential space-based services (Thomas, 2011; Sommer, 2019) and space environmental risks due to the creation of harmful space debris.
Fortunately, actual hostilities have not been conducted in outer space to date. This of course also means that there is no sufficient State practice on the matter so far, but rather much political and legal uncertainty instead, since unfortunately, the jus ad bellum spatialis (the international regime governing inter-State armed force in outer space) is far from being conclusively developed (with manual projects like MILAMOS and Woomera still ongoing) and remains insufficient to appropriately prevent and regulate conflicts in outer space and ensure its continuing sustainability, peacefulness, and security. Various hard law initiatives such as the longstanding disarmament efforts by the UN Conference on Disarmament (UNCD) to conclude a Treaty on the Prevention of an Arms Race in Outer Space (PAROS) and also the ultimately unsuccessful drafting and negotiation process of the Draft Treaty on the Prevention of the Placement of Weapons in Outer Space, the Threat or Use of Force against Space Objects (PPWT) aimed at prohibiting the use of force against (another State’s) space object have been (and will likely remain) unsuccessful due to lacking or diverging State interests when it comes to regulating and especially restricting military uses of the “ultimate high ground” (Sheehan, 2015, pp. 12-13; Mutschler, 2015, pp. 43-48).
While States have failed to formulate a clear prohibition on the use of force in outer space through hard law despite all the increasing risks, I would like to point out in this post how besides the UN Charter and general international space law already prohibiting the use of force against other States’ space objects, especially soft law might play a crucial role in ensuring the continued sustainability, peacefulness, and security of outer space by contributing to the remarkable formation of an international customary norm prohibiting such uses of force and thus fill a dangerous legal gap in the jus ad bellum spatialis. In my opinion, such a customary norm has already started to form through soft law, primarily expressed by a series of consistent and widely supported United Nations General Assembly (UNGA) resolutions on the matter, which can be seen as evidence for existing opinio juris. Furthermore, the absence of open uses of force against space objects in cases of inter-State conflicts can be viewed as concurring State practice on the matter (for now).
First, I would like to briefly revisit how existing hard law – the UN Charter and international space law in particular – already but insufficiently prohibits the use of force in outer space in my view.
The rules of the UN Charter are generally considered to apply in outer space, but are very general themselves, including their well-known sometimes more but often less force-restrictive interpretations. Art 2 (4) of the UN Charter is principally sufficiently broad to also cover (illegal) uses of force in outer space, despite the fact that there cannot be conventional cross-border use of force due to the lack of borders in the res communis environment of outer space where targeted objects are principally outside the territory of any State. This is because Art. 2 (4) of the UN Charter not only prohibits the use of force “against the territorial integrity” of another State, which is conventionally understood as prohibiting cross-border force (Hakimi & Cogan, 2016, p. 257), but also broadly prohibits the use of force “in any other manner inconsistent with the Purposes of the United Nations”. These “Purposes of the United Nations” are laid down in Art. 1 of the UN Charter and are above else “to maintain international peace and security” (Art. 1 (1) UN Charter), which is irreconcilable with using force in outer space. On that basis it has been convincingly argued that the UN Charter use of force prohibition thus also extends to uses of force in outer space (Goh, 2004, p. 263; Cheng, 1997, pp. 70-72; Sommer, 2019, pp. 22-35).
The outer space use of force prohibition is in my view also implicitly reflected in international space law. The international framework regulating outer space activities consists of five multilateral space treaties at the core (most of which today enjoy wide ratification), which were concluded under the auspices of the UN, and nowadays also of various soft law agreements, such as UNGA resolutions, transparency and confidence-building measures, and policy guidelines (Freeland, 2015, p. 91). Many of the space treaties’ provisions have customary international law status today (Lee, 2003, p. 93; Schmitt, 2017, p. 270; in fact, all provisions referenced in this post enjoy such status) and generally, custom and soft law instruments are of particular importance for regulating outer space activities (Cheng, 1997, pp. 127-150; Tronchetti, 2011, pp. 619-633).
The rules of international space law focus almost exclusively on the peaceful uses of outer space and remain largely silent on the issue of the use of force. On the one hand, this entails lacking normative clarity regarding the use of force in outer space, but on the other, it is also indicative of how the international community imagines its shared use of outer space in my opinion and importantly, international space law is linked to the general jus ad bellum regime.
Particularly, the central and widely ratified international agreement on the use of outer space, the Outer Space Treaty (OST), states that outer space use shall be in accordance with international law and the UN Charter (Art. III OST). The jus cogens use of force prohibition as found in the UN Charter as well as in customary international law thus also applies to outer space use.
Furthermore, the so-called “launching States” (Arts. VII OST, I (a) Registration Convention (REG)) retain sovereignty over their space objects under international law by exercising “jurisdiction and control” according to Arts. VIII OST, II REG (Schmidt-Tedd & Mick, 2017, pp. 520-524). This is similar to maritime law and the concept of the “flag state”, which shall also “exercise jurisdiction and control […] over ships flying its flag” (Art. 94 United Nations Convention on the Law of the Sea). In the Nicaragua case, the ICJ held that the “principle of respect for State sovereignty […] is […] closely linked with the [principle] of the prohibition of the use of force”. (para. 212) Since space objects remain under the sovereign control of their respective launching States it is my opinion that the use of force against another State’s space object therefore qualifies as a prohibited use of force (Sommer, 2019, p. 34).
Apart from the general jus ad bellum rules, international space law is clear on the fact that outer space is first and foremost to be used for peaceful purposes (Finch, 1968, p. 365), despite its past and present military use (Goh, 2004, p. 269). Paras. 2 and 4 of the OST preamble first mention the principle of the peaceful purposes of outer space use, which is considered to be customary law (Blount, 2012, p. 2) and appears in almost all UN documents relating to outer space. While the peaceful purposes principle is often seen as indicative of how the international community imagines its shared use of outer space, the fact remains that the international space treaties are largely silent regarding unpeaceful uses of outer space. There is only Art. IV OST which prohibits the placement of WMDs in space.
The lack of sufficient normative clarity under the UN Charter regime and general international space law regarding the legality of using force in outer space contains the risk that States abuse the existing legal gaps or act in a way that others consider unlawful. This could also alter contemporary, force-restrictive interpretations of the jus ad bellum spatialis due to converse State practice. Since it is inconceivable at the moment that the major global space powers will be willing or able to agree on any new space treaty in the foreseeable future due to lacking or diverging State interests, especially with regard to restricting the use of force in outer space or prevent its weaponization (apparent when looking at the unsuccessful drafting and negotiation process of the aforementioned PPWT), looking for other means beside treaty law restricting the use of force in outer space seems appropriate because of the potentially highly adverse effects of space warfare.
A peculiarity of international space law is not only the particular significance of its customary law, which for the past decades has filled and continues to fill the gaps of lacking State support for new UN space treaties and compensates for their inadequacies (Tronchetti, 2011, pp. 619-633), but also that such customary space law is frequently formed through soft law like UNGA resolutions. In its 1996 Nuclear Weapons Advisory Opinion, the International Court of Justice (ICJ) generally stressed the potential relevance of soft law (UNGA resolutions in particular) for the development of customary law:
“The Court notes that General Assembly resolutions, even if they are not binding, may sometimes have normative value. They can, in certain circumstances, provide evidence important for establishing the existence of a rule or the emergence of an opinio juris. To establish whether this is true of a given General Assembly resolution, it is necessary to look at its content and the conditions for its adoption; it is also necessary to see whether an opinio juris exists as to its normative character. Or a series of resolutions may show the gradual evolution of the opinio juris required for the establishment of a new rule.” (para. 70)
One year later, Cheng (Cheng, 1997, pp. 127-150) famously noted the possibility of “instant custom” in international space law with regard to UNGA resolutions and thus underlined the importance of soft law for the development of international space law, which continues to be relevant today.
Since 1959, the UNGA has adopted 64 resolutions on International Co-operation in the Peaceful Uses of Outer Space and 26 resolutions on the Prevention of an Arms Race in Outer Space, almost always with overwhelming support. These resolutions can be considered as authoritative interpretations of the UN Charter in the outer space-context and contribute to the formation of customary international law regarding the prohibition of using force in outer space (Goh, 2004, p. 260). Moreover, the 2017 UNGA Resolution on Further Practical Measures for the Prevention of an Arms Race in Outer Space explicitly encourages all States to actively contribute to the “prevention of […] the use of force against space objects.”
In my opinion, the series of consistent and widely supported UNGA resolutions on the matter can be seen as evidence of emerging opinio juris through soft law prohibiting the use of force in outer space in line with the ICJ’s criteria in its aforementioned Nuclear Weapons Advisory Opinion. Furthermore, the absence of open uses of force against space objects (although clearly feasible from a technical standpoint, as several successful anti-satellite weapons tests in the past have shown) in cases of inter-State conflicts can be regarded as concurring State practice on the matter.
As Cheng has shown, customary international law can rapidly develop from UNGA resolutions. Thus soft law will continue to play a crucial role in regulating space activities in the future and the emergence of an international custom prohibiting the use of force against space objects might provide an exit from the international community’s deadlock with regards to sufficiently regulating the use of force in outer space and could therefore be vital in ensuring the continuing sustainability, peacefulness, and security of outer space and its beneficial use for mankind.
Views expressed in this article are the author’s own and are not representative of the official views of Jus Cogens Blog or any other institute or organization that the author may be affiliated with.
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