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Star Laws: Legal Controls on Armed Conflict in Outer Space

Credit: edobric/Adobe

Credit: edobric/Adobe

By Dale Stephens

An undeclared military space race is unfolding yet there is no clear understanding of how international law operates in the field of armed conflict in outer space.

The idea of space warfare has long dominated movie and television scripts. However, what has been a staple of science fiction is now rapidly becoming an acute reality.

Modern military operations rely heavily on satellites for communications, intelligence gathering, reconnaissance, navigation and targeting. At the same time, space weaponry capabilities are being developed by a number of states. Anti-satellite systems are reaching a stage of developmental maturity and may well be deployed before too long. At present there is an undeclared military space race unfolding, with countries vying for ascendency in this potential theatre of operations.

The idea of warfare in, through or from space is well-accepted within military planning circles. Despite this there is at present no clear understanding of how international law, which applies to regulate armed conflict and to minimise civilian casualties and damage on Earth, operates in the field of armed conflict in outer space.

Modern society relies heavily on space-based assets for modern banking, internet, aviation, commerce, medical, agricultural and other critical civilian activities. An unregulated armed conflict in space threatens these major peacetime civilian activities and represents an unchecked vulnerability to our way of life.

The recent 2016 Australian Defence White paper recognises the need for the international community to develop a “rules-based” system to address the increasing militarisation of space. Despite this, recent international attempts to agree to a framework that regulates the weaponisation of space have proven futile.

A recent initiative by the University of Adelaide Law School in conjunction with McGill University Law School (Montreal, Canada) to develop the Manual on International Law Applicable to Military Uses of Outer Space offers a chance for international legal experts to develop a set of rules that ensures any militarisation is not left unchecked.

Space Weapons

Contemporary military planning fully accepts the reality of warfare in space. In 2005, US Air Force General Lance Lord noted: “Space superiority is the future of warfare. We cannot win a war without controlling the high ground, and the high ground is space.”

The 1967 Outer Space Treaty, to which Australia is a party, prohibits the placement in orbit around the Earth of any nuclear weapons or any other kinds of weapons of mass destruction. Additionally, it prohibits the placement of such weapons on celestial bodies or the stationing of such weapons in outer space. Outside of these express prohibitions, states are not bound by any treaty (or other applicable customary international law) regarding the weaponisation of space.

In recent years there has been development of kinetic anti-satellite (ASAT) weapons that attack targets in space from Earth. Similarly, there has been increasing development of “co-orbital ASATs” – rocket-launched objects that achieve a similar orbital plane as the intended target. Once within orbit, an ASAT can be manoeuvred until it is close enough to physically collide with its target. Given the hypervelocity at which objects can travel in space orbit – approximately 27,000 km/h – such collisions create significant destructive impact.

There has also been work undertaken on electromagnetic pulse, radiation and directed energy weapons along with “soft kill” capabilities such as cyberweapons. Indeed, this last category poses a particular threat given that access to such capability can be relatively easy. Prominent commentator Peter Singer has noted (

It’s not just the big boys who can play at it… Anti-satellite missiles – that’s been within the realm of great powers, like a Russia, a China, a US. It’s not something that a Hezbollah or an al-Qaeda or an ISIS could pull off. With cyber warfare, the barrier to entry is a lot lower.

International Humanitarian Law in Space

International Humanitarian Law comprises numerous treaties and other applicable customary international law. Every country in the world is a party to the four 1949 Geneva conventions that apply to regulate armed conflict on earth. This treaty series is unique in being the only set of treaties where there is universal signature and ratification. Such law only applies to conflicts conducted on land, sea or air. It does not expressly apply to outer space. Despite the lack of express application, it seems highly likely that this body of law would apply to space conflict.

The key features of this body of law are the central principles of distinction, proportionality and precaution.

  • The principle of distinction requires that armed forces only direct their military action against enemy combatants and military objectives.
  • Proportionality requires that, when attacking a military objective, an attacking force must make an assessment about the military advantage anticipated from such an attack and measure that gain against the expected civilian loss that will be suffered. Where that loss is not “excessive”, the attack is lawful.
  • The principle of precaution requires that an attacking force take all “feasible”precautions in the choice of means and methods of attack with a view to avoiding, and in any event to minimising, incidental loss of civilian life, injury to civilians and damage to civilian objects.

    In respect of the principle of distinction, it is well settled that “dual use” objects may be lawfully attacked. Hence, objects that have both a military and civilian function can be lawfully attacked, at least while they still have a military function. This includes airports that are used by civilian and military aircraft, railway yards that convey military equipment, ports that allow for warship use, and satellites that are used for both civilian and military use. This would include civilian satellites that acquire and pass on militarily significant information relating to reconnaissance, electronic intelligence, early warning systems, ocean surveillance systems (that can detect surface and subsurface movement), radar calibration, communications and meteorological data. Such satellites may have other purely civilian applications, but to the extent they are used for even a single military function they lose their civilian protection.

    Interestingly if there was a conflict between two belligerent states and each had deployed military astronauts into outer space, then each would be potentially targetable by the other. In the event they are captured in space then they would acquire prisoner-of-war status under the third Geneva convention. In the event that they returned to Earth following some kind of armed exchange, then should they land in an emergency in the opposing belligerent country they would also acquire prisoner-of-war status and be kept in confinement until the end of the conflict.

    Paradoxically, however, the 1968 United Nations agreement on the rescue and return of astronauts mandates that astronauts shall be returned to their country of origin. This would represent a legal conundrum as to which treaty regime would have precedence.

    If a satellite is designated as a military objective under the law, then the next question in the targeting decision sequence is one of proportionality. This is often assessed in terms of anticipated but unavoidable loss of civilians who are living or working in the immediate vicinity of a military objective. There is no mathematical rule defining what is an acceptable civilian loss, but courts have required that an objective “reasonableness” test be applied. In the space context, the issue is less about direct civilian loss but rather indirect civilian loss.

    At present, unmanned aerial vehicles (UAVs) require access to satellite navigational services. Indeed, many of the world’s precision munitions are similarly reliant on global navigational satellite systems, whether it is the US GPS system, Russian GLONASS system, the developing Chinese Bei Dou system or more recently the regional Indian NAVIC system. To this end, such satellite constellations are lawful targets given their connection with military uses.

    The question of proportionality then arises. Would the military advantage of undermining the enemy’s capacity to use such UAVs/munitions be so great that the loss of something like GPS/GLONASS would be “excessive” to the military advantage anticipated? If it’s not considered excessive, then they may be lawfully attacked.

    International civilian communications, navigation, commerce and the Internet are dependent upon a functioning global navigational satellite service. The resulting civilian loss would be enormous, however the legal test is not “extensive” loss overall but rather “excessive” loss to the anticipated military advantage. It may well be that global navigation satellite systems should derive some special legal protection from attack given its ubiquitous civilian use, but as yet such an idea has not been advanced.

    The question of precautions in attack has particular relevance in the field of space-based warfare. While physical means of attacking satellites have been proven, the resulting debris created from using a missile, or otherwise creating actual damage to a satellite, poses a significant problem.

    In 2007, China launched a direct ascent ASAT missile to destroy an ageing Chinese weather satellite. The targeting created a debris field of more than two million pieces of up to 10 cm in size. By 2009, the US was still tracking almost 2400 fragments that could be detected with Earth-based sensors. Such objects pose a significant safety danger

    Accordingly, military planners must account for the fact that in any given physical attack, thousands of pieces of debris will likely rotate the Earth at enormous speed, and hence are capable of the destruction of all objects in their path. The projected trajectories of the debris and planned orbits, and possible resulting collisions, must be taken into account in the military legal planning process.

    Military commanders must also have regard to the “Kessler syndrome” when analysing a consequence of resulting debris. Donald Kessler stressed in the 1970s that when debris is travelling at hypervelocity in an area of dense satellite or other space object concentration, there is significant potential for space debris to multiply as a result of subsequent collisions. Such potential has an exponential effect and is theoretically mappable to an infinite scale.

    Given these sobering facts, the principle of precaution might mandate that kinetic means are not to be used when attacking an enemy military satellite. Rather, there may be a requirement to use cyber means or perhaps a highly specific directed energy weapon to disrupt the function of a satellite without destroying it.

    The Way Forward

    In the absence of a formal agreement regarding military activities in space, The University of Adelaide Law School and McGill University Law school have taken the initiative in drafting a Manual of International Law Applicable to Military Uses of Outer Space ( The drafting process commenced in May 2016 and will last 3 years. The process has drawn about 40 international legal experts in the fields of Space Law, Use of Force and International Humanitarian Law.

    Previous international operations law manuals like this one have been drafted for naval warfare, air and missile warfare and cyberwarfare. These manuals have had a durable impact in military operational thinking and planning.

    The consequences of an unrestrained armed conflict in outer space are too serious to ignore.

    Dale Stephens is Director of The University of Adelaide’s Research Unit on Military Law and Ethics.