Why is the United States’ announcement of weapons in space noteworthy?

Having operational weapons in space is not necessarily new or surprising. For decades, major powers such as the United States, China, and Russia have been developing and testing anti-satellite (ASAT) weapons, including systems that can be placed in orbit. However, what is new is that the statement constitutes the first public acknowledgment that the United States has a specifically designed space weapon stationed in orbit.

In his announcement last month, Air Force Secretary Troy Meink provided some limited transparency regarding the increasingly militarized nature of outer space and the prospect of an arms race there. “We are increasing readiness against existing threats, and the United States has on-orbit space control weapons capable of defending the joint force against hostile adversary action,” Meink said. Space is generally recognized as a warfighting domain, and states developing ASAT technologies that can degrade, disrupt, or destroy their adversaries’ satellites is, for good or ill, a fact of operating within that domain. The weaponization of space remains a pressing concern for states and for international organizations like the United Nations.

Why now?

The principal rationale appears to be deterrence signaling, especially to the United States’ main adversaries in space, China and Russia, which have each developed ASAT weapons programs. The announcement might, therefore, be viewed as a calibrated response to U.S. rivals’ behavior, one that simply recognizes that all three states have been developing ASAT technologies, including those that can be placed in orbit, for a long time. In addition to deterrence, some limited transparency offered by the U.S. disclosure might be regarded as bringing stability to an increasingly contested domain. Some worry, however, that the announcement instead turns up the heat in orbit, with the weaponization of space becoming increasingly normalized, and prompts China and Russia to augment their existing capabilities to counter undisclosed U.S. technologies. Other states might also follow suit by developing and deploying their own space-based weapons, which increases the risks of proliferation and contestation in space to the detriment of both states and private commercial actors that operate there.

What type of weapons are we talking about? 

States tend to keep these cards close to their chests, and Meink did not provide details of the nature, number, and placement of the weapons in orbit.

However, he did speak of “space control weapons,” which refers to the U.S. policy of seeking to achieve and maintain “space superiority,” including through the use of ASAT technologies, which are typically grouped into four broad categories:

1. Kinetic physical ASAT weapons, such as anti-satellite missiles or other methods of physical kinetic attacks directed against satellites (such as projectiles, robotic arms that can grab satellites, and chemical sprayers)
2. Non-kinetic physical ASAT weapons, including lasers and high-powered microwaves
3. Electronic ASAT weapons, such as jamming devices that interfere with the transmission of signals to and from satellites and spoofing devices that can falsify such signals
4. Cyberattacks against space systems

Depending on the technology, the weapon might be launched from Earth (including land, sea, and air platforms) or from orbit, and it might also be used against land-based space infrastructure, such as satellite ground stations.

Experts have speculated that the “space control weapons” referred to by Meink are orbital weapons and likely to be electronic warfare or radio jamming platforms, rather than the kinetic and more destructive type of weapon, although the latter cannot be ruled out.

How have U.S. adversaries responded?

Negatively. China cautioned against an arms race in outer space, and Russia asserted that space must be free of any weapons. Russia also reiterated the call for a “legally binding instrument” that would prevent the use of force against space objects. The United States has previously been critical of Chinese and Russian proposals for a dedicated treaty banning the placement and use of weapons in space due to a lack of effective means to verify compliance with any treaty.

With these responses, China and Russia are ostensibly setting themselves against war in space. Yet a recent U.S. assessment shows that both states continue to develop their own ASAT weapons, with the threat growing in scale, complexity, and aggressiveness. Space experts agree that China and Russia are developing a range of ASAT capabilities, in addition to other states like Iran, North Korea, India, Israel, and some European states, to varying and lesser degrees. The greatest fear relates to Russia, which might be developing a nuclear space-based weapon as part of its arsenal. This would be a uniquely dangerous threat to us all. Accordingly, the space environment is increasingly unstable, and this is before other emerging technologies, such as autonomous space systems powered by AI, are added into the mix.

What have U.S. allies said?

Very little publicly, with the exception of the UK. Following the U.S. announcement, the UK likewise confirmed that it is “developing capabilities for orbital warfare.” The UK also announced the creation of a Royal Air Force squadron dedicated to defending UK satellites from hostile threats. In 2023, France publicly declared its intention to build and launch a satellite equipped with a high-powered laser, so signaling the importance of space and of protecting space assets seems to be a recent theme. It will be worth watching whether other allies now follow suit.

Is it legal under international law for the United States to deploy ASAT weapons in space?

The United States is unlikely to have breached existing international law simply by deploying a space-based weapon. However, the legality of its conduct would ultimately depend on how that weapon is used.

Article IV of the Outer Space Treaty of 1967, which is the main space law treaty, explicitly bans placing nuclear weapons and other weapons of mass destruction in orbit, installing them on celestial bodies, or otherwise stationing such weapons in outer space. The moon and other celestial bodies are also fully demilitarized by Article IV and may only be used for peaceful purposes. However, international law does not prohibit other types of weapons, including conventional ASAT weapons placed in orbit. States may use these technologies for lawful purposes, such as necessary and proportionate acts of self-defense conducted in accordance with international humanitarian law.

Specific international legal regulation of ASAT weapons is currently lacking, although there are laudable ongoing multilateral efforts to prevent an arms race in outer space. The UN General Assembly has called for all states to commit to not conducting destructive ASAT missile tests, and several states, including the United States, have unilaterally agreed to this. However, a multilateral ban on placing and using ASAT weapons is unlikely in the current geopolitical climate.

Without a multilateral ban, how can ASAT weapon use be limited?

The focus of my recent and ongoing research has been to think about how existing international law applies to ASAT weapon use, even when states use these weapons in self-defense (which Meink appeared to contemplate). My argument is that, without a multilateral ASAT weapons control treaty, there are bodies of international law, not originally conceived of as applying beyond the Earth’s atmosphere, that can be interpreted and applied to space. These bodies of law include (but are not limited to) international law governing the use of force (anchored in the UN Charter) and international humanitarian law, which both set limits regarding when and how states may lawfully target satellites using ASAT technologies, including in self-defense. 

Although the current U.S. administration is dismissive of international law, states generally accept that it applies in space. The United States, NATO, and EU allies have previously expressed their commitment to responsible behavior in space and to acting in space in accordance with international law. Given the unique nature of the space environment and the importance of satellites to modern societies, compliance with these rules means that ASAT weapon use of all kinds—even in defensive military operations—would be heavily restricted and may even be prohibited in all but the most extreme circumstances of self-defense. Just because you deploy a weapon in space does not mean that you get to use it freely, without considering the ramifications.

Why is limiting ASAT use so important?

Tactically, targeting an adversary’s satellites with ASAT weapons could offer a state a significant military advantage in conflict. Modern militaries rely heavily on satellite-provided services to conduct warfare, so neutralizing your adversary’s satellites reflects the idea that whoever wins in space also wins on Earth.

Yet the ramifications of ASAT weapon use for states, corporations, and individuals could be disastrous. Potential space debris resulting from ASAT weapon use (especially of the kinetic kind) can be incredibly long-lasting and threatens all other satellites in orbit. Many of these satellites underpin the operation of global societies and economies. Take U.S. GPS and its equivalents. Although many may think of this technology’s role in mapping apps and fitness trackers, GPS is central to running many essential services, including agriculture, aviation, banking systems, power grids, emergency services, and more. Conflict in space leading to even a temporary GPS disruption could therefore have catastrophic effects on civilians and state interests, both on Earth and in space.

This is why space debris caused by ASAT weapon use has been emphasized by the United States itself as a major concern, including in response to the controversial Russian ASAT missile test in 2021. As space becomes increasingly congested with ever more satellites being launched by states and private actors, the potentially catastrophic risk posed by ASAT weapon use multiplies. We must avoid making space unusable.

How does the law address these risks?

The law allows states to effectively defend themselves, but within guardrails that require states to account for the consequences that flow from targeting an adversary’s satellite during conflict.

Non-kinetic methods such as jamming, laser dazzling, spoofing, and limited cyber operations against satellite systems must be preferred to using destructive kinetic ASAT weapons. The latter type of weapons should generally be regarded as off the table to avoid the risk of space debris and civilian harm. Earth-based targets, such as satellite control centers, should also be preferred over targeting satellites with any form of ASAT weapon. Indeed, as recent events show, targeting supporting terrestrial infrastructure might be just as effective as directly targeting the satellites themselves and avoids the risks of conducting warfare in space. The imperative to protect space and space-provided services from the effects of military activities in this way benefits us all, including the strategic interests of the United States. My argument is that compliance with the existing law reflects and protects this essential need.

What will you be watching for as this story evolves?

Other states’ responses will be interesting to note, especially if the U.S. announcement encourages other states to follow suit because it is viewed as a further legitimization of space-based weapons. The next meeting of the UN working group on this topic is scheduled for November, and I am keen to see if this and other multilateral arms control efforts can make progress and keep pace with the rapid technological developments that we are witnessing.

I will also be watching to see if the push for restraint filters beyond typical expert groups and brings further transparency to state actions. Perhaps the announcement by Meink can shine a light on the existence and capabilities of these weapons and the potentially catastrophic dangers that they pose to our everyday lives here on Earth. I hope this renewed focus will spur the development of meaningful regulation and (re)commitments by states to responsible behavior in space.