Defining The Line: Why The Department of Defense Should Reconsider United States Space Command’s Area Of Responsibility

By: Ashley Torkelson
Approximate Reading Time: 10 minutes

On 29 August 2019, United States Space Command (USSPACECOM) was reestablished as a geographic combatant command.  The establishment included an announcement regarding the area of responsibility (AOR) as “the area surrounding the earth at altitudes equal to or greater than 100 kilometers above mean (average) sea level.”  Statements regarding the AOR for a geographic combatant command are routine, but, this time the remarkably precise definition has unprecedented implications, including the potential creation of binding international law.

The line drawn by USSPACECOM of 100 km is not unique; it is referred to as the Kármán Line.  This altitude was historically utilized as the demarcation from air space to outer space.  It is the height at which aircraft can no longer conventionally fly and must instead enter orbit to stay in air. Though, despite this widely used standard, there still exists immense hesitation in the international community to codify this precise line as the start of outer space.

Nowhere in the Outer Space Treaty,[i] the four other treaties regarding space,[ii] or the National Space Policy of the United States is there a defined line.  The United States State Department has previously expressed the nation’s stance of delimitation of outer space at the United Nations General Assembly’s Committee on the Peaceful Uses of Outer Space (COPUOS), noting that a definite line should not be drawn until “absolutely necessary,” as doing so would be “arbitrary at worst, or, at best, be constrained by the current state of technology.”  In fact, the National Defense Authorization Act (NDAA) for 2020 authorizing the United States Space Force includes no mention of a defined line marking the beginning of space.

Hesitation to affirmatively define a line is not without fair reason.  The United States Air Force has awarded astronaut status to those who reached 12 miles below the Kármán Line,[iii] while the joint space doctrine defines space as the “area above the altitude where atmospheric effects on airborne objects become negligible.”[iv]  Indeed, a recent study argues that the true Kármán Line is between 70 km and 90 km, not 100 km.[v]  The debate has even caused the Fédération Aéronautique Internationale, the organization responsible for aeronautic and astronautic records, to propose an international workshop to explore a reduction in the altitude marking the boundary of space. This begs the question, what effect does USSPACECOM’s policy have?

The Recipe for International Law

International law is derived from formal international agreements or customary international law.[vi]  Customary international law comes from a “general and consistent practice of states, followed by them from a sense of legal obligation.”[vii]  In examining what constitutes customary international law, the first prong—a general and consistent practice—need not be extraordinarily long in duration, as long as it is general and consistent.[viii]  This objective factor can be reflected in documentary or oral evidence including policy statements, press releases, and “official manuals on legal questions, e.g. manuals of military law[.]”[ix]

The second prong is subjective in nature and is referred to as opinio juris, or the belief by a state that there is a legal obligation to follow a custom.  Outer space has been a breeding ground for opinio juris beginning 4 October 1957, when the Soviet Union launched the world’s first satellite, Sputnik, into orbit.  By sending a satellite into space with disregard for sovereign affairs, the USSR implicitly communicated its belief that outer space was free domain.  President Eisenhower, at the time disinterested in aspects of space exploration outside of military strategy,[x] responded with congratulatory tones: “We congratulate Soviet scientists upon putting a Soviet satellite into orbit.”  This groundbreaking moment and the resulting reaction not only began an international space race, but it also put into motion what later became customary international law, later codified in formal international agreement.  Article II of the Outer Space Treaty ensures that outer space, including celestial bodies, may not be claimed as sovereign territory.[xi]


In what could be argued as a first ingredient to creating international law, USSPACECOM formally announced the AOR as the area at or above 100 km above sea level and its intent to “lead space campaign planning and employment.”[xii]  In discussing the decision, General John Raymond, USSPACECOM Commander, noted, “We did that to solidify space as a warfighting domain and to allow us to have a clear, tighter partnership with the other geographic combatant commands and other combatant commands that we have to operate with.”

“We did that to solidify space as a warfighting domain and to allow us to have a clear, tighter partnership with the other geographic combatant commands and other combatant commands that we have to operate with.”
-General John Raymond

USSPACECOM’s announcement that its warfighting domain is contained at 100 km and above potentially satisfies the first requirement of customary international law.  This is because continued statements, both oral and documentary, can produce a general consistent practice.  The continual marketing of the statement infers that the United States will act under the premise that space begins at 100 km.  Acts can include anything from procurement to military orders to a new joint doctrine.  Should an obligation to the line develop, the cement of customary international law begins to harden.  And when one considers the Combined Force Space Component Command—which works with the United Kingdom, Australia, New Zealand, and Canada—falls under this AOR, that assumption is harder to overcome if these nation states are also accepting that line and acting on it in day-to-day operations.

Why It Matters

The above scenario may seem like an unlikely slippery slope, and one in which assumptions are made that the Department of Defense (DoD) alone can create international law despite internal disagreement within the government.  But, it should not diminish the significance of the AOR.  USSPACECOM’s published AOR is a consequential step because it has massive legal implications.  The line at which outer space begins changes the legal analysis from one of sovereign airspace into one of free use and exploration under international law.  Importantly in military operations, it also changes considerations in the law of armed conflict.[xiii]  An offensive movement by state actors into our sovereign territory is easy to observe and respond to whereas actions in outer space blur the line of even simple questions like what is an offensive act?[xiv]  Thus, by defining the AOR and set responsibilities for USSPACECOM, the DoD has positively identified its floor at which space operations, and in turn space law, begins: 100 km above sea level.

By establishing this floor, the AOR may create future obligations on the DoD, and arguably the nation, to abide by international law while above 100 km but respect state sovereignty below 100 km—even where a space object may survive below that line.  This thinking can dramatically hamstring our ability to utilize highflying objects above enemy territory, or alternatively, how we react to adverse objects flying slightly below 100 km.  These effects can be even more pronounced where the AOR language may not only obligate us to what we say, but it may also inadvertently create binding international law.  Any future operational deviations from the line may then require reconciliatory measures in light of Space Policy Directive-4, which mandates protection of our nation’s interests in space “consistent with applicable law, including international law[.]”[xv]

Hypersonic technologies highlight the potential concern with a hard-drawn line.  Hypersonic glide vehicles travel at speeds of at least five times the speed of sound, remain maneuverable in flight, and fly at altitudes up to 100 km.  Due to both speed and altitude, hypersonic missiles have the potential to evade traditional anti-missile and anti-aircraft systems.  Russia is expected to be the first to test a hypersonic missile from a nuclear powered cruise missile submarine in 2020.  Based upon the above assumptions, under USSPACECOM’s current AOR, use of force determinations—which in this case must be made extraordinarily quickly—may considerably vary in the fleeting, unpredictable moments the vehicle moves above and below the line.

OTH, Emerging Security Environment, Multi-Domain Operations

Figure 1. Main Layers of the Atmosphere

How We Can Avoid A Permanent Outcome

The creation of customary international law can be halted in its tracks by an objection to its application.  When another nation state uses our published AOR as proof that the United States believes space begins at 100 km, the United States need only deny its legal effect.  A state that dissents from a custom during its formation as customary international law is generally not bound by it.[xvi]  A similar situation occurred due to an Australian statute defining launch as above 100 km, forcing the nation to explain at COPUOS that the statute’s definition “was not an attempt on Australia’s part to define or delimit ‘outer space’[.]”

To frontload these statements, the DoD could also ensure that every time the AOR is mentioned in publication or orally, the product reflects a disclaimer stating that USSPACECOM’s AOR is for operational purposes only and does not reflect the United States’ legal position on the beginning of space.  The United States utilizes a similar disclaimer in the DoD Law of War Manual.[xvii]

Both options are feasible and have a high likelihood of success, but publishing the AOR prepositions us in a defensive stance.  The United States government must be hyper-vigilant to this language being used as an official line, or ensure that the DoD includes a disclaimer anytime the AOR is mentioned.  Additionally, the benefits of stating a solid line—primarily, domestically laying claim to resources and funds—are not insurmountably more than operating under an expanded, widely-used standard of space beginning around 100 km.

Therefore, USSPACECOM and a future United States Space Force should veer from defining a domain with precision and instead utilize the current joint space doctrine definition of space as the “area above the altitude where atmospheric effects on airborne objects become negligible.”[xviii]  By doing this, USSPACECOM can ensure that it maintains a dynamic AOR that can respond to technological advances while avoiding inadvertently boxing itself into disadvantageous legal regimes.


As our nation, and in particular, our military, grows its presence and capabilities in space, it should be of paramount importance that we cautiously approach what we say, what we write, and the actions we take in space. On a larger scale than ever before, we must recognize that our words matter and they have incredible consequences.  In this case, the words defining a specific, precise AOR are unnecessarily hampering and have little net value added. USSPACECOM would benefit by expanding the lines of the AOR and aligning it with the joint space doctrine definition of outer space as the area above the altitude where atmospheric effects on airborne objects become negligible.  USSPACECOM should therefore redefine its geographic AOR to simply “outer space.”

Capt Ashley Torkelson is an attorney in the United States Air Force currently assigned to the 30th Space Wing at Vandenberg Air Force Base. 

Disclaimer: The views expressed are her own and not those of the United States Air Force or Department of Defense.

Feature Image: Common Altitudes Above the Surface of the Earth


[i] Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, Jan. 27, 1967, 1967 U.S.T. 613, 18 U.S.T 2410 [hereinafter Outer Space Treaty].

[ii] See Agreement on the Rescue of Astronauts, the Return of Astronauts and the Return of Objects Launched into Outer Space, Dec. 3, 1968, 19 U.S.T. 1968; Convention on the International Liability for Damage Caused by Space Objects, Mar. 29, 1972, 24 U.S.T. 2389, 961 U.N.T.S. 187; Convention on Registration of Objects Launched into Outer Space, Nov. 12, 1974, 28 U.S.T. 695, 1023 U.N.T.S. 15; Agreement Governing the Activities of States on the Moon and Other Celestial Bodies, Dec. 18, 1979, 18 I.L.M. 1434.

[iii] Dean N. Reinhardt, The Vertical Limit of State Sovereignty, 72 J. Air L. & Com. 65, 88 (2007) (citing Air Force Instruction 11-402, Aviation and Parachutist Service, Aeronautical Ratings and Badges, July 29, 2003, para. 2.3.2).

[iv] Joint Chiefs of Staff, Joint Publication 3-14, Space Operations, U.S. Department of Defense (Apr. 10, 2018).

[v] Jonathan C. McDowell, The Edge of Space: Revisiting the Karman Line, Acta Astronautica, Vol. 151 (Oct. 2018), available at

[vi] Restatement (Third) of the Foreign Relations Law of the United States § 102 cmt. c (1987).

[vii] Id. at § 102(2).

[viii] Id. at cmt. b.

[ix] James Crawford, Brownlie’s Principles of Public International Law 21–22 (9th ed., 2019).

[x] Moonrise: SPUTNIK! (The Washington Post podcast published Aug. 27, 2019).

[xi] Supra n.1 at art. II.

[xii] Advance Policy Questions for General John W. “Jay” Raymond, USAF Nominee for Appointment to be Commander, United States Space Command, U.S. Senate Armed services committee, 6 (Jun. 4, 2019).

[xiii] See Matthew T. King, Sovereignty’s Gray Area: The Delimitation of Air and Space in the Context of Aerospace Vehicles and the Use of Force, 81 J. Air L. & Com. 377, 387, 395–98 (2016) (“Thus, in assessing the propriety of the use of force, or the likelihood of the use of force in the event of the overflight by an aircraft or space craft, whether the craft is in sovereign territory is an essential factor.”).

[xiv] See id. at 491–92 (acknowledging that offensive capabilities can be achieved by orbital vehicles but arguing that orbital objects are inherently passive due to their inability to control their flight).

[xv] Space Policy Directive-4, Establishment of the United States Space Force, § 3(a) (Feb. 19, 2019) (emphasis added).

[xvi] Supra n.6 at cmt. d.

[xvii] See U.S. Dep’t of defense law of war manual 7 (2015) (“[T]he mere citation of a policy or regulation in this manual should not be understood to reflect the view that the policy or regulation’s requirements have been promulgated out of a sense of legal obligation for the purposes of assessing customary international law or otherwise intending to reflect legal requirements.”).

[xviii] See supra n.4.

Print Friendly, PDF & Email

One thought on “Defining The Line: Why The Department of Defense Should Reconsider United States Space Command’s Area Of Responsibility

  • February 1, 2020 at 9:56 pm

    If I can find time, I’ll write a more lengthy response to this as I was the USSPACECOM Deputy AO at the UCP write conference arguing for an AOR. Last I saw, there were disclaimers highlighting the AOR definition had no intent to snap a chalk line on where space started on various documents I had. Additionally, a hypersonic missile inbound to the US skipping below or above the AOR doesn’t have any practical impact on whom is responsible for determining whether there is an attack against the US (just as a Russian ICBM isn’t USEUCOM’s ‘responsibility’ while within Russian airspace). That responsibility for attack determination is actually highlighted in another section of the very same UCP. For the purposes of an AOR, it sets boundaries for the CCDR responsible for planning and implementing military strategies, operations, and interorganizational coordination and that’s it. Dynamic AORs are bad, as it leads to a lack of clarity for our allied partners or other agencies on whom they are to coordinate with. Lastly, per Ashley’s point, if an international body or nation-state attempted to use the AOR line as a demarcation point, the USG could easily highlight other places where defined AORs had no legal or international basis for establishing precedent. For example, USEUCOM has the state of Israel within its AOR, however few will argue Israel is a European country. Bottom line, the AOR definition provides further refinement for CCDR responsibilities over a physical region of space (pardon the pun), which allows other CCMDs, US Gov agencies, and international partners to know who to coordinate US military matters within that new AOR. I agree this new language will require some clear messaging but overall senior US government officials were well aware of the positives and negatives of such a declaration and sided with establishing USSPACECOM with an AOR.


Leave a Reply