NATIONAL HARBOR, Md.— The U.S. military’s top uniformed leader says U.S. forces must be ready for war near or possibly even on the moon, a rhetorical leap that comes as service leaders are still wrestling with the legal frameworks surrounding its newly revealed orbital weapons.
“Our task, my friends, is to adapt right now, so the Joint Force is prepared to fight, endure, and win, in global contested environments, from the seabed to cislunar space,” Joint Chiefs Chairman Gen. Dan Caine told airmen, guardians, and industry figures during his keynote address at the Air, Space, and Cyber Conference.
Caine later repeated the thought—“today’s modern battlefield operates from the seabed to cislunar space”—but he did not clarify whether he meant on the moon’s surface. U.S. law is ambiguous, defining cislunar space as “the region of space from the Earth out to and including the region around the surface of the moon.” At least one Harvard Law Journal article interprets the clause to mean on the moon itself, and the White House’s National Cislunar Science and Technology Action Plan explicitly said in late 2024 that it includes the lunar surface. But the Air Force Research Laboratory’s 2021 “Primer on Cislunar Space” appears to treat space and the moon’s surface as two different domains.
Caine pointed to recent comments made about orbital weapons by the Air Force secretary and the Space Force’s chief of space operations. Top space force officials have been hesitant to provide more details on how they would operate in that domain and how they’d responsibly use space weapons in future conflicts.
While top Space Force officials have provided few details about how U.S. forces would fight between the Earth and its moon, they have been vocal about adding sensors and capabilities to watch adversary movements there. Aaron Brynildson, a space law professor at the University of Mississippi said it’s understandable why the military would want to increase awareness within that region.
“There’s a fear that recent Chinese activity on the moon and in cislunar space might outpace the United States,” Brynildson said. “China has a relay satellite in cislunar space and is performing robotic missions on the far side of the moon.”
The Outer Space Treaty of 1967, which the U.S. signed, outlaws certain military behaviors on the Moon and states that it shall be used “exclusively for peaceful purposes.”
“The establishment of military bases, installations and fortifications, the testing of any type of weapons and the conduct of military manoeuvres on celestial bodies shall be forbidden. The use of military personnel for scientific research or for any other peaceful purposes shall not be prohibited.”
Space Force Lt. Gen. Gregory Gagnon, the head of Combat Forces Command, told reporters during a media roundtable that the 18th and 19th Space Defense Squadrons are now both sharing the cislunar mission among each other.
“Our adversaries, our potential adversaries, such as the PRC, are actively pursuing activities in the cislunar parts of space. So that’s sort of the expansion, if you will, of I would say the end zone, if you will, in the football game,” he said.
When asked if the Outer Space Treaty limits the military’s cislunar ambitions, Gagnon said it did not limit orbital operations.
“The United States Space Force will continue to execute safe and responsible space operations in all regions of space and in all orbits,” he said.
Brynildsonn said that while the treaty forbids the creation of military bases on the moon, “The U.S. needs better capabilities in cislunar space to ensure China complies with that obligation and doesn’t militarize the moon. There’s a real coverage gap by the U.S. that needs closing.”
This week’s revelation by Air Force Secretary Troy Meink and Chief of Space Operations Gen. Douglas Schiess that the U.S. has on-orbit space-control weapons has raised legal questions about their responsible use. Experts have speculated that the weapons are likely non-kinetic, such as jammers and electronic warfare capabilities.
When asked whether U.S. policy limits the use of a kinetic space weapon, meaning a destructive capability that would cause debris, Gagnon deferred to policy offices.
“So we have capabilities in the military because we are preparing to defend the nation. The reason we have capabilities is to help create deterrence,” he said. “When you go to war, you break things.”
Brynildson said it’s not clear how current laws limit the use of space weapons.
“It’s unclear what the legal restraints on the use of kinetic or non-kinetic weapons in space might be. The Outer Space Treaty doesn’t give us great answers to what factors a military action must consider,” he said. “The DoD Law of War Manual is also non-committal on the unique aspects of the space domain. At a minimum, general principles from the law of armed conflict would apply, such as only striking military-related satellites, avoiding collateral damage to civilians, etc.”
U.S. lawmakers are also concerned by the lack of space-focused military legal knowledge. A provision inserted by the Senate Armed Service Committee in the 2027 National Defense Authorization Act tasks the Defense Department with assessing its “space law requirements” to face rising threats and examine “options for establishing a dedicated legal organization within the Air Force, Space Force, or Space Command.” The amendment adds that senators are “concerned that current legal, policy, and institutional structures within the Department of Defense may not have kept pace with the complexity of space operations.”
Those clarified legal norms may not emerge until it’s too late.
“Ultimately, I think the first space conflict might be the time when most of these rules get written,” Brynildson said.
