Lindsay Bernsen Wardlaw
Vol. 40 Online Content Editor
In March 2018, United States President Donald J. Trump publicly proposed the creation of a new branch of the U.S. armed forces: The Space Force. Yet, the U.S. is a party to the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies (the Outer Space Treaty), which restricts parties’ ability to militarize space.
Whether the Outer Space Treaty prohibits a U.S. Space Force depends, in large part, on just what the Space Force is – and on how we interpret the Outer Space Treaty itself.
What is the Space Force?
Vice-President Mike Pence has indicated that the Space Force will be an independent sixth branch of the military. It will be comprised of employees currently spread throughout the U.S. military, including Air Force Space Command. The administration hopes that consolidating these employees and their existing tasks into a single chain of command will reduce duplication of their workloads and help the U.S. government implement a cohesive strategy for U.S. engagement in space. 
Critically, the Space Force will include a new U.S. Space Command, which will be led by a four-star general or flag officer, “responsible for directing the employment of the Space Force” to use “space assets in warfighting and accelerate integration of space capabilities into other warfighting forces.” In particular, the Department of Defense (DOD) outlines several warfighting goals: Surveillance and targeting of missile threats; development of GPS alternatives and node-independent command and control options (to minimize vulnerability in the event the U.S. is attacked); and “deterrent capability,” including ground-based launch infrastructure. The DOD also discusses the need for the Space Force to counter specific threats from other countries, particularly Russia and China, who are developing techniques to incapacitate U.S. satellite infrastructure, such as anti-satellite missiles, lasers, and electronic warfare, as well as satellite jamming.
Functionally, then, we can categorize the Space Force’s most controversial potential activities as: (1) the use of satellites for reconnaissance and military support, (2) the development of anti-satellite measures and satellite defenses, (3) the coordination of ground-based missile launches through sub-orbital and orbital ranges, and (4) according to some commentators, the establishment of a military presence in space. Each of these potential activities will need to be independently evaluated for compliance with the Outer Space Treaty.
Would Space Force Activities Violate the Outer Space Treaty?
The pertinent provisions of the Outer Space Treaty are in Article IV, which states:
- States Parties to the Treaty undertake not to place in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner.
- The moon and other celestial bodies shall be used by all States Parties to the Treaty exclusively for peaceful purposes. The establishment of military bases, installations and fortifications, the testing of any type of weapons and the conduct of military maneuvers on celestial bodies shall be forbidden. The use of military personnel for scientific research or for any other peaceful purpose shall not be prohibited. The use of any equipment or facility necessary for peaceful exploration of the moon and other celestial bodies shall also not be prohibited.
Textually, then, even though the Trump administration has discussed the Space Force primarily in “warfighting” terms and even though it is establishing the Space Force as a military branch, most of the activities that the Space Force is predicted to engage in – except (4) (establishing a military outpost on the moon or another planet) – should be permissible under the Outer Space Treaty. Consider: Article IV(1), on its face, appears to apply only to orbital activities, placing a broad ban on weapons of mass destruction (WMDs) in Earth’s orbit but not on much else. Article IV(2), in turn, appears to only apply to activities on the moon or other celestial bodies, the use of which must be restricted to “peaceful purposes.” On this reading, the use of space, outside of the moon and celestial bodies, need not be exclusively for peaceful purposes. In that case, using orbital satellites for reconnaissance and military support is acceptable; so long as they are not WMDs, they may be placed into orbit. It is also acceptable, on this reading, to deploy anti-satellite defenses, unless they are characterized as WMDs (a characterization that, though unconventional, might be plausible if the devices could take out sufficient navigation, communications, or weather satellites at the right moment). Even launching ground-based missiles – which might be equipped with nuclear payloads or otherwise considered weapons of mass destruction – should be acceptable on a strictly textualist reading; they launch through sub-orbital or orbital ranges but they are not “placed in orbit.”
However, this is not the only potential reading of Article IV. There is a compelling argument that, under traditional international law rules for the interpretation of treaties (particularly, under Article 31 of the Vienna Convention on the Law of Treaties), Article IV should be read in the context of the remainder of the Outer Space Treaty, particularly its Preamble, Article I, Article III, and Article IX, and of the U.N. Charter.  In this light, both Article IV(1) and Article IV(2) require the use of space for “peaceful purposes” – whether the activity takes place in orbit or on the moon or another celestial body, and the restriction might even include uses of space that primarily impact earth, such as the use of reconnaissance satellites and other dual-use items.
But even if we must read Article IV(1) as requiring the use of orbital space for “peaceful purposes,” it isn’t immediately clear that the Space Force’s activities would be disqualified (except for the establishment of a military outpost on the moon, which remains explicitly prohibited). Why? It is debatable whether “peaceful purposes” are non-military purposes or merely non-aggressive purposes. Non-aggressive purposes appear to include stationing military satellites in space for self-defense and therefore may also include stationing weapons or other military tools in space for the same reason.
Currently, most countries with an active space presence or who use space-derived capabilities seem to accept the latter interpretation. This draws strength both from the fact that the U.N. Charter allows self-defense and from the decades-long custom of using space-derived capabilities to support the military.  In particular, the use of satellites for reconnaissance, communications, navigation, and weather forecasting by the military is no longer controversial, nor is the use of ground-based missiles for self-defense. The use of anti-satellite weapons is also likely permissible.
Ultimately, whether we interpret the Outer Space Treaty textually or contextually, the activities of the U.S. Space Force are probably permissible under international law. If that feels like the wrong result to you, especially when the administration has been clear about its intent to use the Space Force for military ends, then it may be time to consider overhauling international space law.
 Announcing the Space Force program to the Miramar Marine Corps Air Station in San Diego, California, President Trump said, “Space is a war-fighting domain just like the land, air, and sea.” President Trump Remarks in San Diego, California, C-Span (Mar. 13, 2018), https://www.c-span.org/video/?442479-1/president-trump-delivers-remarks-san-diego-california. Similar ideas were floating in the press even before President Trump’s announcement; in July 2017, a bill passed by the House of Representatives to create a “space corps” within the Air Force. Russell Bermann, Does the U.S. Military Need a Space Corps?, The Atlantic (Aug. 8, 2017), https://www.theatlantic.com/politics/archive/2017/08/military-space-corps/536124.
 U.S. Dep’t of State, Bureau of Arms Control, Verification, & Compliance, Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies, https://www.state.gov/t/isn/5181.htm [hereinafter the Outer Space Treaty] (listing signatories) (last visited Oct. 22, 2018).
 Dartunorro Clark, Pence Launches Space Force, Says U.S. Needs to Prepare for ‘Next Battlefield’, NBC News (Aug. 9, 2018), https://www.nbcnews.com/politics/white-house/vp-pence-lays-out-trump-s-vision-establishing-u-s-n899176.
 U.S. Dep’t of Defense, Final Report on Organizational and Management Structure for the National Security Space Components of the Department of Defense (2018), https://media.defense.gov/2018/Aug/09/2001952764/-1/-1/1/ORGANIZATIONAL-MANAGEMENT-STRUCTURE-DOD-NATIONAL-SECURITY-SPACE-COMPONENTS.PDF; see also Clark, supra note 3.
 U.S. Dep’t of Defense, supra note 5.
 Leonard David, Will the US Military Space Force’s Reach Extend to the Moon?, Space.com (Sep. 27, 2018), https://www.space.com/41943-space-force-extend-earth-moon-space.html.
 The Outer Space Treaty, Jan. 27, 1967, 18 U.S.T. 2410.
 See Gennady Zhukov & Yuri Kolosov, International Space Law 57 (1984) (considering the Outer Space Treaty to require “‘total neutralization and demilitarization of celestial bodies and (only) partial demilitarization of outer space”); J.E.S. Fawcett, Outer Space, New Challenges to Law and Policy 15 (1984) (stating that “there is no provision” that outer space itself, as opposed to celestial bodies, “shall be used exclusively for peaceful purposes”); Nandasiri Jasentuliyana & Roy S. Lee, Manual on Space Law 439 (1979) (noting that “during the debate on the Outer Space Treaty in the General Assembly several delegations questioned the propriety of excluding outer space from the coverage of the second part of Article IV because to do so would create the implication that outer space may be used for non-peaceful purposes.”).
 Fawcett supra note 11, at 15; see also Robert L. Bridge, International Law and Military Activities in Outer Space, Akron L. Rev. 649 (1979).
 See Kimblery M. Schlie, Developing and Deploying Laser Weaponry in Space: Is It Legal?, 4 DePaul Int’l L.J. 17, 24 (2000) (claiming that the Outer Space Treaty “creates a loophole for weapons such as lasers which are purported to be used for targeting specific and limited sites such as missiles or satellites, thus escaping the definition of a weapon of mass destruction”).
 Bill Boothby, Space Weapons and the Law, 93 Int’l L. Stud. 179, 202-03 (2017).
 Vienna Convention on the Law of Treaties art. 31(1)-(2), May 23, 1969, 1155 U.N.T.S. 331, (entered into force Jan. 27, 1980) [hereinafter Vienna Convention]. Under the Vienna Convention, a treaty’s terms are to given their “ordinary meaning” “in context,” which includes, “in addition to the text [and] the preamble and annexes”: (a) any agreement relating to the treaty which was made between all the parties in connexion with the conclusion of the treaty; [and] (b) any instrument which was made by one or more parties in connexion with the conclusion of the treaty and accepted by the other parties as an instrument related to the treaty.” Though the U.S. remains a non-party to the Vienna Convention, Article 31 is generally considered to have entered into the body of customary international law, and as such, may bind the United States. See Evan Criddle, The Vienna Convention on the Law of Treaties in U.S. Treaty Interpretation, 44 Va. J. Int’l L. 431, 445-48 (2004).
 See Richard A. Morgan, Military Use of Commercial Communication Satellites: A New Look at the Outer Space Treaty and “Peaceful Purposes”, 60 J. Air L. & Com. 237, 302 (1994) (“This second school of thought concludes that the language, [from the Outer Space Treaty’s Preamble] ‘common interest of all mankind,‘ the ‘benefit of all peoples,‘ ‘broad international cooperation,‘ ‘furthering the purposes of the U.N.,‘ [from the Outer Space Treaty’s Article I] ‘use in accordance with international law,‘ [from the Outer Space Treaty’s Article III] ‘maintaining peace and security,‘ ‘promoting international cooperation‘ and [from the Outer Space Treaty’s Article IX] ‘having regard for the interests of other States,‘ found in the Outer Space Treaty are principles which serve to define what uses may be made of outer space. As such, they also serve to define the meaning and applicability of the clause ‘peaceful purposes.‘”); see also Boothby, supra note 14, at 201 (2017).
 See A. Ferreira-Snyman, Selected Legal Challenges Relating to the Military Use of Outer Space, with Specific Reference to Article IV of the Outer Space Treaty, 18 Potchefstroomse Elektroniese Regsblad 488, 497-98 (2015), http://www.scielo.org.za/pdf/pelj/v18n3/03.pdf.
 Morgan, supra note 16, at 303-305.
 Id. at 303.
 Id. at 307-308; see also Andrew T. Park, Comment, Incremental Steps for Achieving Space Security: The Need for a New Way of Thinking to Enhance the Legal Regime for Space, 28 Hous. J. Int’l L. 871, 893-896 (2006).
 See William J. Lynn, III, A Military Strategy for the New Space Environment, 34 Wash. Q. 7, 8 (2011) at 7, 10 (quoting the then-Deputy Secretary of Defense asserting, “Space systems enable our modern way of war. They allow our warfighters to strike with precision, to navigate with accuracy, to communicate with certainty, and to see the battlefield with clarity. Without them, many of our most important military advantages evaporate . . . . [T]oday we rely on space for almost everything we do”); see also David A. Koplow, The Fault Is Not in Our Stars: Avoiding an Arms Race in Outer Space, 59 Harv. Int’l L.J. 331, 335 (2018).
 See Carl Q. Christol, The Use of Outer Space for Peaceful Purposes, Legal & Political Considerations, 28th Colloquium on the Law of Outer Space 4 (1985) (finding the use of reconnaissance satellites an “accepted practice”/”peaceful purpose”); Morgan, supra note 16, at 307 (concluding that commercial communications satellites used by the military should be considered similarly acceptable).
 Burrus M. Carnahan, The Legality of a High-Technology Missile Defense System: The Abm and Outer Space Treaties, 78 Am. J. Int’l L. 418, 423 (1984).
 The acceptance of anti-satellite defenses is suggested by: (1) The fact that, while the U.S. and the Soviet Union both had forms of anti-satellite defenses in the 1950s and 1960s, these defenses weren’t explicitly mentioned in the Outer Space Treaty. Koplow, supra note 21, at 340. (2) The fact that, after a brief attempt to craft a separate anti-satellite defense treaty in the late 1970s (after the creation of the Outer Space Treaty, so presumably under the impression that such defenses weren’t covered by it), the U.S. and the Soviet Union gave up. Id. at 349-50. And (3) the fact that when China launched its first anti-satellite missile test (on a Chinese satellite), the U.N. took no action on the subsequent U.S. complaint. Adam G. Quinn, The New Age of Space Law: The Outer Space Treaty and the Weaponization of Space, 17 Minn. J. Int’l L. 475, 476 (2008).