III SISL – SERIES OF SEMINARS ON INTERNATIONAL SPACE LAW, LEICESTER, UK
Francesca Giannoni-Crystal speaking on the panel “Militarization and Weaponization in Space”
Place: Leicester Space Park
Date: 22 May 2025
I’m Francesca Giannoni-Crystal, an international lawyer based in Washington, D.C. In addition to my private practice, I serve as outside in-house counsel for the Pasquali Microwave Group, which manufactures components for the space and defense sectors, particularly in the areas of microwaves and composites.
I have recently published an article in the Harvard National Security Journal addressing the legality of defending national activities on the Moon, especially as states and commercial actors increasingly compete for access to a limited number of strategically valuable lunar locations.
The Cislunar and Lunar domains are poised to become increasingly contested as national space strategies evolve to integrate military objectives.
The Space Force’s Guide to Space Warfare (title: Space Warfighting – A Framework for Planners), [1] which can signal a paradigm shift: the U.S. is no longer simply protecting its space assets, but is now openly preparing for contested operations, including in Cislunar space, with a full spectrum of tools aimed at deterring, defending, and prevailing in a space conflict scenario. Interestingly the document explicitly includes the cislunar domain in its strategic considerations(even if does not specifically mention the lunar surface).[2]
The reality is, only a few spots on the Moon –like the Peaks of Eternal Light, the radio-quiet zones on the Far Side, and some areas near the poles– are truly viable for long-term activity. These locations are extremely limited and already drawing attention from multiple parties. And that creates risk: the risk of interference, of accidents, and potentially even escalation. As lunar missions become more complex and permanent, states are going to want to protect their people, equipment, and infrastructure.
In my article, I ask whether states can lawfully defend their activities on the Moon when they’re threatened or interfered with. My answer is yes. Some form of defense is going to happen anyway and having clear legal recognition of that right can actually help prevent conflict. It brings stability and clarity.
Let me break this down. Under Article 51 of the U.N. Charter, states have an inherent right to self-defense if an armed attack occurs—and that right applies everywhere, including outer space. There’s no exception for the Moon, in my opinion.
Now, some people point to Article IV of the Outer Space Treaty and claim that all military activity on the Moon is banned. But that’s not exactly what the text says. Article IV(1) prohibits weapons of mass destruction and nuclear weapons. Article IV(2) doesn’t say anything about self-defense. In fact, it prohibits “the establishment of military bases, installations and fortifications, the testing of any type of weapons, and the conduct of military maneuvers” on celestial bodies (it also includes two exceptions, which I explored in detail in my article: the use of military personnel for scientific or other peaceful purposes, and the use of equipment or facilities necessary for peaceful exploration.)[3] Importantly, Article IV says nothing about self-defense. Some scholars point to the part where it says celestial bodies must be used “exclusively for peaceful purposes” to argue that any use of force, even in self-defense, would be prohibited. But when you interpret that clause in the broader context of the Treaty, when you read “peaceful” to mean “non-aggressive” (which is the dominant view among spacefaring nations), and you interpret vi-a-vis the UN Charter, to me, all of this points toward self-defense remaining lawful.
That interpretation aligns with Article III of the Treaty, which incorporates the U.N. Charter—including the right to self-defense under Article 51—and really, international law in general. So to me, the OST and the U.N. Charter aren’t in conflict—they have to be read together.
And we can already see that major spacefaring states, including the U.S., China, Russia, and NATO countries, are preparing to defend their assets in space. We already mentioned the U.S. Space Force document—which isn’t cited in my article because it was published after—but my article does refer to other documents, principally national space strategies, that clearly express an intent to defend space assets. So based on this, defense on the Moon isn’t just a theoretical possibility—it’s expected.
Now, I know some worry that recognizing a right to defense might fuel militarization. But I actually think the opposite is true. Legal clarity reduces the chance of miscalculation. If actors know in advance that interfering with lunar activities could trigger a lawful defensive response, they’re less likely to take risky steps. That kind of clarity helps us avoid escalation before it starts. Also, it is necessary to clarify that militarization and weaponization aren’t the same thing. Militarization means the use of space by military actors; this already happens (it includes satellites, surveillance, communications, even logistics). Weaponization, on the other hand, is about placing or using weapons in space or on celestial bodies. So when we talk about lawful defense or deterrence on the Moon, we’re often talking about militarization in a broad sense; not weaponization. I am not saying that weaponization is not a risk.
But … let’s face it: lunar operations are going to be delicate. Comms will be fragile, things will break, and misunderstandings could spiral fast. That’s why we need a clear legal framework, where deterrence is based on known rules, not guesswork.
And honestly, it makes sense. Companies already use private security on Earth to protect critical infrastructure—why wouldn’t they do the same on the Moon? I don’t take a position in the article on whether the Outer Space Treaty applies directly to private actors. But what I do point out is that, under Article VI, states are responsible for national activities in space, including those carried out by private entities. So if companies start deploying security teams, the state will need to keep a close eye—because ultimately, it’s the state that’s accountable…
Conversation prompts:
- What is the most relevant topic in the current militarization/weaponization of space — and how should it be addressed?
Honestly, I think the most urgent issue isn’t hypothetical weapons in orbit—it’s how states are going to defend their lunar activities. The Moon is quickly becoming a crowded and competitive environment. We’re not just talking about potential conflict between nations, but also private actors operating side by side in high-stakes areas like the Peaks of Eternal Light. My paper argues that the legal framework—especially the U.N. Charter and the Outer Space Treaty—already permits self-defense, and states are preparing for it. What we need now is clarity. Legal clarity, operational coordination, and real attention to how defense can coexist with the principle of “peaceful purposes.”
2.How will militarization and weaponization shape the future of:
- Lunar exploration
It’s going to define lunar exploration. If we don’t clarify what kinds of defensive measures are legally acceptable, we’ll see uncertainty, and with uncertainty comes the risk of miscalculation. Defensive actions need to be lawful, proportionate, and expected—not improvised after the fact.
- ISRU (In-Situ Resource Utilization)
ISRU might be exactly what will trigger protection needs. The more valuable lunar resources become, the more likely actors will want to defend their operations. My view is: ISRU and defense planning are going to grow hand in hand. And unless there’s some baseline understanding of what’s lawful, we risk disputes escalating fast.
- Legislation and governance
We’ll probably see more national legislation or practice that defines acceptable behavior, also when it comes to private actors. But I’m not optimistic about international coordination. Honestly, I think the era of broad, multilateral space treaties might be over—at least for now. That’s likely to leave us with a patchwork system, which could lead to fragmentation and instability.
- Commercialization
Commercial actors will want security for their operations, as they invest a lot money there —and they’ll push for state backing if they can’t ensure that security on their own. So states are likely to get pulled into defending private activities.
3. What should we expect in the short- and medium-term?
I believe, in the short term, we’ll see more declarations—like national space strategies or like the Space Force’s document —acknowledging the need to defend space infrastructure. In the medium term, I expect we’ll see actual deployment of systems—communications, monitoring, maybe even automated security assets—intended to protect lunar sites. The line between “security” and “militarization” might be blurry quite fast.
4. What is your “wish list”?
- Ideal support/environment to perform your role
Honestly, I believe I would want to see a more coordinated legal discussion between national security lawyers and space lawyers/academia. We need cross-disciplinary engagement, because the issues –conflict, compliance, deterrence– span both fields.
- What do you need from experts outside your field?
From people outside the legal field, what I really need is perspective. From technical experts: help us understand what defense might actually look like on the Moon; what systems are realistic, what capabilities are being developed. From policymakers: we need leadership on lunar defense, before problems arise, not just after.
5.Imagine you are a newcomer to this topic — what would you tell yourself?
- What to do
Start by learning the basics: the Outer Space Treaty, the U.N. Charter, and the general principles of the law of armed conflict. These are the foundation.
- What opportunities to pursue
There’s real space –no pun intended– for scholarship and policy work here. Lunar defense is still a developing conversation. And I believe space lawyers, especially those who take into account realpolitik—what countries actually intend to do in space, are going to be more and more essential.
- What to avoid
First of all—we all want to avoid a Star Wars situation, right? But at a more practical level, I think the real thing to avoid is binary thinking: military vs. civilian, peace vs. war. Lawful defense doesn’t mean you’re weaponizing the Moon. We need to recognize—or at least, this is my view—that some protective measures, some degree of deterrence, may actually be necessary and even stabilizing. And maybe that’s how we start addressing the risks and threats of militarization and weaponization in cislunar and lunar space: by acknowledging what’s realistically on the horizon, and focusing on responses that are stabilizing, not escalatory.
Final remarks
Defense of national activities on the Moon isn’t some distant scenario — it’s already part of how spacefaring countries are thinking. For me, the main point is this: defense in cislunar and lunar space is going to happen. The question isn’t if, but how. I believe that protective measures –and some forms of deterrence– are compatible with the Outer Space Treaty, and can actually contribute to stability. I guess it’s more militarization to avoid weaponization. If we stay realistic about the risks and thoughtful about the legal and policy tools we use, we have a real chance to keep this next phase of lunar activities relatively stable.
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[1] The framework has been defined as most detailed guide yet for conducting warfare “in, from, and to space;” the aim of the document is to introduce a standardized lexicon for “guardians” and joint planners, with the central aim of securing space superiority, which we can defined as ensuring freedom of movement for U.S. forces in space while denying the same to adversaries. The Framework defined “space superiority”: “A degree of control that allows forces to operate at a time and place of their choosing without prohibitive interference from space or counterspace threats, while also denying the same to an adversary.”
[2] The document lists offensive and defensive actions that the military may pursue. For example: offensive actions like orbital Strike (e.g., direct physical attacks on satellites), space Link Interdiction (via electromagnetic attacks, e.g., jamming or spoofing signals or Cybernetwork Attacks, e.g., satellite hacking), terrestrial Strikes originating from: ground-based, Maritime, Airborne, space-based fire systems. Defensive actions: active Space Defense (e.g., escort missions, counterattacks, suppression of adversary systems), passive Space Defense such as: threat Warning systems, Disaggregation and Mobility of space assets (ie, disaggregation means spreading out functions that were traditionally concentrated in a single satellite or system into multiple smaller, distributed assets; mobility refers to the ability of a space asset to change its orbit or position in space, either proactively or reactively), redundancy and Hardening to ensure continuity of operations, Military Deception and Dispersal to reduce targetability (misleading adversaries about the nature, location, capabilities, or intentions of space assets or operations.)
[3] In my paper, I discuss how Article IV(2) of the Outer Space Treaty applies only to activities conducted on celestial bodies—not to their orbits. So in my view, it doesn’t prohibit the lawful stationing of military personnel in lunar orbit. I also point to one of the exceptions in Article IV(2): the use of military personnel for peaceful purposes. That would clearly cover support roles—like a military corps handling logistics, similar to how air forces assist with infrastructure and transport in Antarctica.
