Should Anti-Satellite (ASAT) Weapons Be Deployed at All?

The growing development of Anti-Satellite (ASAT) weapons has often asked the question of whether their use is legal in the international regime. While the answer to that may be affirmative (with caveats), the question one might ask is can ASATs be placed in orbit around the Earth at all?

What Really Are Anti-Satellite Weapons?

Anti-Satellite Weapons or ASATs are a type of counterspace weapon that can be used to target, disable or destroy a satellite in space. They can be used to protect a nation should another nation try to use their satellites for an undesignated or possibly illegal activity. Currently, only four (4) countries have a successful ASAT program, which puts them far ahead than any other country in the space race- United States of America (1959), Russia (1968), China (2007), and India (2019).

Broadly classified, there are two (2) kinds of ASAT weapons- kinetic and non-kinetic. Kinetic energy weapons physically clash into the targeted satellite, destroying the target and itself, whereas the non-kinetic weapons use cyber-attacks or Electromagnetic Pulses (EMPs) to disable the satellites from a distance. While kinetic ASATs are more violent destroying the satellite completely, the non-kinetic ASATs have a more discreet and invisible advantage making them more likely to be used in space warfare.

Are They Legal?

Every space related activity is internationally governed by the Outer Space Treaty, 1967, often also called as the foundational space law treaty. This treaty, coming into force in 1967, lacks an explicit mention of ASATs. However, the treaty does prohibit the placing into orbit or anywhere in space any nuclear weapons or weapons of mass destruction (WMDs) in Article IV. The treaty also prohibits testing and by extension use of any military weapons or maneuvers on celestial bodies. The treaty is by and large silent on the use of conventional weapons, let alone counterspace weapons.

A general principle in international law is that what is not explicitly prohibited by a treaty, regulation, or any other binding document, is permissible. This principle was explained in the Lotus case, wherein the Permanent Court of International Justice said (page 19):
“Far from laying down a general prohibition to the effect that States may not extend the application of their laws and the jurisdiction of their courts to persons, property and acts outside their territory, it leaves them in this respect a wide measure of discretion which is only limited in certain cases by prohibitive rules; as regards other cases, every State remains free to adopt the principles which it regards as best and most suitable.”

This freedom to adopt its own principles is not absolute. Every international activity is still subject to the rules and principles of the United Nations (UN) Charter. Article 2, paragraph 4 puts a general prohibition on States from the threat or use of force against any State. The Advisory Opinion of the International Court of Justice on the Legality of the Threat or Use of Nuclear Weapons clarified that the provisions in the UN Charter ‘do not refer to any specific weapons’ and Charter neither prohibits nor permits the use of any weapon. The Court further clarifies that if the use of force itself is illegal, the threat of the same would be too. Thus, the use of ASAT weapons is neither explicitly permitted, nor explicitly prohibited. The use of ASATs may then amount to a use of force, unless done in accordance with the fundamental principles of necessity and proportionality (discussed below). However, what about the mere placement of ASATs in the orbits? Does that not amount to the ‘threat’ to use force?

Is Their Mere Presence a Threat?

Two years ago, the US White House confirmed having intelligence on the development of Russia’s nuclear anti-satellite, which was again flagged by US Space Command Gen Stephen Whiting in April 2026 as a warning. This caused wide concern and condemnation from the international community as this, if confirmed, would be an outright violation of the Outer Space Treaty and many other disarmament and nuclear-ban treaties such as the Partial Test Ban Treaty, which Russia is a state-party of. The news also brought to light how all of us are dependent on space technology for our day-to-day lives – GPS, communications, financial and global internet systems, etc. The deployment of that nuclear ASAT in the Low Earth Earth orbit could impact over 10,000 satellites handling these systems.

Of course, the nuclear ASAT is already prohibited by the sole virtue of it being a nuclear weapon with the Outer Space Treaty in force. Article I of the Partial Test Ban Treaty also prohibits testing nuclear weapons or any other explosions in the outer space, which too would be violated by the deployment of the ASAT.

It is clear that (a) the use of the ASAT may amount to the use of force (necessity and proportionality discarded), and, (b) the alleged Russian nuclear ASAT is violative of multiple treaties by it being nuclear in nature. But this begs the question if the mere deployment of any ASAT would or should be prohibited. One of the reasons for prohibiting the alleged nuclear ASAT is that if deployed it could hamper multiple satellites and with them many global communication, finance and defense networks. Such is the case with any other ASAT. ASATs are developed and programmed with the intent to destroy a satellite, which could mean a lot of damage to the satellite State and in some extreme cases, the civilians. By the mere nature of it being a ‘counter’-space ‘weapon’, it violates the peaceful use of outer space standard set by the Outer Space Treaty.

If the ASAT deployed is a kinetic energy weapon, the collision between the ASAT and the target-satellite would lead to a huge increase in the already increasing space debris. The estimated number of events that have resulted in the fragmentation of objects in space is more than 660 as per the European Space Agency. This number is expected to increase as the number of satellites or debris-collisions increase around the Earth. This increasing debris and chances of collision are just what Donald Kessler predicted in 1978, which later on came to be generally referred as the Kessler Syndrome– “Satellite collisions would produce orbiting fragments, each of which would increase the probability of further collisions, leading to the growth of a belt of debris around the Earth”.

Source: The European Space Agency (https://www.esa.int/ESA_Multimedia/Images/2008/03/Debris_objects_in_low-Earth_orbit_LEO2)

If the mere deployment of an ASAT in space has the potential of causing such wide array of harm to any State, with almost none having a space-defense system of their own, would this not qualify as a ‘threat’ to the use of force by the deploying country?

One counter-argument is that any reasonable State or leader would need an adequate reason to threaten any other State or indicate their potential to use force. However, just as the US-Russia example shows, no explicit statements need to be made by any State for another to be cautioned or take preventative actions when it is already recognized that something harmful is constantly hovering over your head. In other words, the mere deployment of any kind of ASAT is still a threat to the use of force because of the nature of the weapon itself and the damages it could do to the target satellite and resultantly to the State and citizens.

A Nation’s Right to Self Defense?

One of the primary reasons any ASAT-capable State will give for placing ASATs is that it is for the purposes of self-defense – in the event that another State decides to harm the former using space-technology. However, they are both subject to the rules of the UN Charter and Article 51 does give every State the right to act in self-defense if an armed attack were to take place. The International Court of Justice in the Case Concerning Military and Paramilitary Activities In and Against Nicaragua (Merits) (‘the Nicaragua case’) affirmed the customary international law standards of necessity and proportionality, which any self-defense act must be in compliance with.

Establishing necessity and proportionality when it comes to space is onerous. A State can indeed establish necessity if the case may be, but the use of ASAT is far beyond proportional. This is so because of the harm that ASAT weapons cause to the targeted satellite, the inconvenience and potential harm to the civilians, and the increase in the space debris causing traffic in space. And should a fragment from the debris damage a third nation’s satellite, the Liability Convention lacks a definite mechanism for redressal since it would be difficult to establish fault on either country.

The Way Forward?

ASAT weapons, therefore, require regulation, if not complete prohibition. A new and comprehensive international treaty prohibiting or regulating the deployment of ASATs needs to be contemplated bearing in mind the UN Charter and threat of force. The treaty and regulations must also prioritize transparency, so that no State has to contemplate whether another State has deployed an ASAT or not.

Given the rapid technological advancements and privatization, it is pertinent that the law develops simultaneously and evolves to accommodate challenges which were once inconceivable. As George Wald, an American Scientist, once said, “Nuclear weapons offer us nothing but a balance of terror, and a balance of terror is still terror”. The law and the international community must now realize that ASATs have now a similar capability of inducing terror and no attempts at balancing this terror would eliminate the terror itself.