The Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies of 1967, also known as the Outer Space Treaty (OST), has long emphasised the need to use outer space for peaceful purposes, particularly when it comes to celestial bodies like the Moon. Along these lines, it becomes important to note the spreading international acceptance of the Artemis Accords (Accords) with Australia being one of the first to sign back in 2019 and most recently, Brazil becoming the first South American nation to sign. The objective of this international effort is to promote utilisation of space resources, particularly the recovery of resources from the surface or subsurface of celestial bodies like the Moon and Mars and other objects like asteroids and comets (Section 10 of the Accords).
In this context, there could arise a situation where these resources are applied for military purposes, which then brings up the question as to the legality of such use. Thus, is important to understand what exactly the term “peaceful” means in the context of the OST and existing customary international law (CIL).
The law and its blind spots
Article IV of the OST requires only the ‘Moon and other celestial bodies’ to be used exclusively for peaceful purposes. This indicates that the peaceful use standard strictly applies to celestial bodies. The only activities expressly banned in the rest of outer space are the placing in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, or the stationing of such weapons.
However, the term “peaceful purposes” is not defined within the OST. While the stated purpose of the Accords is to enhance the ‘enhance the governance of the civil exploration’ (see Section 1), it still opens channels for activities like mining that utilise resources on the Moon and on Mars. Thus, the need of the hour is to clearly demarcate the line between peaceful and non-peaceful use. For instance, if a mineral mined on the Moon was used to enhance the effectiveness of a nation’s weapons on Earth, would this violate Article IV of the OST?
Broadly, two lines of thought have emerged in interpreting what exactly constitutes peaceful use- the first aligning such use with anything that is ‘non-aggressive’, and the second interpreting the term to prohibit any military use of celestial bodies.
Option one: Peaceful purposes translates to non-aggressive use
A good way to justify this interpretation is on the basis of the general rule that treaties are interpreted by assigning the ordinary or customary meaning to terms (See Article 31(2) of the Vienna Convention on the Law of Treaties and Gardiner). Dr Alex Meyer applies this rule to the OST by looking to the Charter of the United Nations (UNC), where the term “peaceful” is ordinarily regarded to mean “non-aggressive” (Also see Smirnoff, who builds on Meyer). This means that as long as the use does not amount to a threat or actual use of force, it would be permissible even if it is clearly for military purposes. Such an interpretation is strengthened when read with Article III of the OST, which requires State Parties to carry out activities in outer space in accordance with international law, specifically the UNC. This link is also featured in Section 3 of the Accords, which requires activities undertaken by signatories to be exclusively for peaceful purposes and in accordance with relevant international law.
If we were to look to maritime law, an analogy quite commonly drawn in interpreting space law owing to the res communis nature of both outer space and the high seas, it permits military use not amounting to aggression. Perhaps of more direct relevance is the Agreement Governing the Activities of States on the Moon and Other Celestial Bodies (Moon Treaty), which at Article 3(2) reiterates the principle of prohibition of the threat or use of force on the Moon.
Practically, this would seem to be the standard favored by space powers, with countries like the United States of America expressly recognising the term “peaceful” as used in the OST to mean non-aggressive use and not non-military (a standard they have maintained even prior to the OST). This is important to note as it plays into the idea of subsequent practice as a means of treaty interpretation as per Article 31(3) of the VCLT (see Vlasic). Given the large extensive military use of outer space (not celestial bodies though), such as use of satellites for military reconnaissance, it is possible to prove international acceptance of the US interpretation.
However, the biggest flaw underlying this line of argument is the express demarcation drawn between the standards for peaceful use of celestial bodies versus the rest of outer space, the standards for the former clearly being higher. Thus, to attribute state practice on the military use of the rest of outer space to support a similar standard on celestial bodies seems counter intuitive. Moreover, given than the Moon Treaty has very little acceptance internationally, with the United States itself not being a signatory, it is a questionable source of state practice.
Option two: Peaceful purposes translates to non-military use
An alternative view on the requirement of peaceful use is supported by many academics like Dr Bin Cheng, who interpret the same to prohibit all military use of celestial bodies (also see Schrog and Neumann in Vol. 1 of the Cologne Commentary). Thus, such a standard requires complete demilitarisation. As Cheng points out, Article 1 of the Antarctica Treaty of 1959, which is what formed the basis of Article 4 of the OST, also requires the region to be used exclusively for peaceful purposes and the same goes on to prohibit any measures of a military nature. Thus, given that the source of the Article IV of OST clearly goes the demilitarisation route, there is a strong presumption that the same would hold for celestial bodies.
An interesting argument put forward by Cheng is that the standards under Article 2(4) of the UNC is really the bare minimum—all it does is restrict any acts done “for aggressive or aggression purposes”, i.e., the threat or actual use of force. Thus, the specific provision in Article IV of the OST must require something above and beyond the normal UNC prohibition. By this, even the use of space assets to enhance the military effectiveness of weaponry would violate Article IV of the OST.
Since there really hasn’t been any state practice of using celestial bodies for any military purpose, complete demilitarisation does seem to be currently indicated by CIL. However, given how rapidly the rest of outer space was militarised, it is very much possible that state practice could change just as quickly. For Australia this is doubly concerning, because it is not a party to the OST but also the Moon Treaty, which reiterates and reinforces the peaceful purpose requirement.
Outer space is, of course, the realm of instant CIL. The Accords have attracted the consent of some of the most significant players in outer space (though it does not include China and Russia, nor does this seem to be a possibility), whose conduct greatly influences state practice in Space Law. As noted by Malcolm Shaw, “for a custom to be accepted and recognised it must have the concurrence of the major powers in that particular field”. Thus, the activities undertaken as a part of the Accords could open up an opportunity to definitively shape the ambit of “peaceful purposes”, either concretising or changing the course of CIL on the issue.
Manasa S Venkatachalam is currently in the final year of the five-year Bachelor of Laws program at Gujarat National Law University, India. Her areas of interest include Public International Law and International Commercial Arbitration. She has worked with Dr. Aniruddha Rajput in his capacity as a member of the International Law Commission, as well as international organizations like the Commonwealth Human Rights Initiative and the Institute for Internet and the Just Society.