Guest post: “For DoD Counter-Drone Operations Above Domestic Military Installations, Fourth Amendment Concerns Are Not Worth Worrying About . . . Yet”
Today’s post welcomes a new contributors to Lawfire®, Army Major Hannah Miller and Air Force Major Ashley Johnson. Writing in their personal capacities, Majors Miller and Johnson discuss the growing problem of unauthorized drone flights over military installations within the United States, and grapple with the Fourth Amendment implications.
For DoD Counter-Drone Operations Above Domestic Military Installations, Fourth Amendment Concerns Are Not Worth Worrying About . . . Yet
by Hannah M. Miller and Ashley N. Johnson
In the past few years, incursions of small unmanned aerial systems (sUAS) over military installations within the United States have skyrocketed. Department of Defense (DoD) officials, lawmakers, and commentators worry about drones spying on, disrupting, or—worst case—attacking the military’s sensitive sites and missions.
While DoD has enjoyed some statutory authority to conduct domestic counter-UAS (C-UAS) operations since 2017 under 10 U.S.C. § 130i, recent high-profile drone incursions have highlighted DoD’s so-called “limited” and “constrained” ability to lawfully conduct C-UAS operations.
There is so much to say on this topic, and so little practical guidance currently out there for installation commanders and their legal advisors. Dawn Zoldi’s posts on Lawfire are a great place to start understanding the broader domestic c-UAS context. We hope to tackle several dimensions of the military-specific problem set in a series of posts on Lawfire about DoD’s homeland C-UAS authority.
Today’s focus is constitutional search and seizure questions. Congress explicitly reminds us in 10 U.S.C. § 130i that the statute must be construed in a “manner consistent with the fourth amendment.” And fears about enabling broad government surveillance on Americans stymied recent efforts to expand the C-UAS authority of other agencies.
So we know the Fourth Amendment remains relevant, both to operations that result in the capture or destruction of aircraft and to operations that collect data from the aircraft or ground control system.
Ultimately, we argue that most C-UAS detection and mitigation operations against drones entering airspace above military installations would generally not violate the Fourth Amendment, even if they collect data or result in damage or destruction to the drone. This analysis could change in the future if basic, commonplace electronic mitigation operations hypothetically evolve into sophisticated cyber operations capable of collecting detailed personal information from a drone operator’s cell phone.
Glorified Gate Runners?
Let’s first explain exactly why drones cannot fly above military installations. While the federal trespass statute, 18 USC § 1382, does not explicitly apply to aircraft trespasses, officials use it regularly against people who enter installations without authorization, including those who seek to take photos without permission.
Trespassers may also commit a misdemeanor if they violate a defense property security order issued by the Installation Commander pursuant to the Internal Security Act, 50 U.S.C. § 797, which could hypothetically include anti-drone language.
The Federal Aviation Administration (FAA) uses 14 C.F.R. § 99.7 to prohibit non-official UAS flights at nearly all installations “from the ground up to 400 feet above ground level,” and most civilian sUAS cannot legally fly higher that 400 feet as a general rule. Flying lower than that 400 foot level (or running afoul of a more specific special security instruction or military airspace classification) constitutes a misdemeanor under 49 U.S.C. § 46307.
Operators may also violate 18 U.S.C. § 39B(b) if their UAS gets too close to an installation’s active runway. Finally, under the Espionage Act, it is illegal to photograph, map, or otherwise graphically represent “vital military installations” without permission, and to use aircraft for the same, as Chinese student Fengyun Shi discovered after allegedly spying on Norfolk shipyards in 2024.
Courts have long recognized that inspections of persons and property entering closed installations represent limited exceptions to the Fourth Amendment, either as administrative inspections or under the theory of implied consent.
Another way to conceptualize this is that people generally lack a reasonable expectation of privacy (REP) in items they send onto other’s property via trespass. Alternatively, the plain-view doctrine could allow military police to lawfully seize an item without a warrant when its incriminating nature—flying in restricted airspace—is immediately apparent.
Just as people who trespass on post may sometimes be apprehended with little force, drones could possibly be captured without sustaining damage (e.g. jammed or spoofed into a controlled landing). Often, however, seizing drones will require damaging them, either by employing passive barriers, kinetic attacks, or altering their flight paths to result in falls or collisions.
The trespass analogy suggests that such forceful UAS seizures may be acceptable. Vehicles are often damaged and their occupants sometimes even injured—or killed—when “gate-runners” attempt to breach a military installation and security personnel deploy protective barriers.
While intuitively appealing, the trespass analogy could easily be taken too far. For example, it offers little granular assistance in cases where electronic detection and mitigation equipment collect data from the UAS.
The Remote ID Case, Restricted Airspace, and Expectations of Privacy
In rejecting a facial challenge to the FAA’s requirement that drones broadcast “digital license plate” information, the D.C. Circuit penned the most significant case law on this topic to date, with three lessons for installation incursions. First, operations that merely locate or track drones above the installation will not trigger the Fourth Amendment because operators have no REP in the physical location of their drones.
Second, we may infer from the Court’s analysis that if operating in the highly regulated public airspace reduces REP for drone operators, operating in even more highly regulated—restricted—airspace should reduce those expectations even more.
Finally, detection operations that discover the mere location of the system controlling the drone also likely pose no Fourth Amendment issue, because, as the Court notes, this reveals nothing qualitative about the operator’s relationship to his location (e.g. for example, whether he’s standing in his back yard).
The Automobile Exigency
Even if an operator’s privacy or possessory interests are enough to trigger Fourth Amendment protections, and the trespass analogy cannot overcome them, the automobile exception to the warrant requirement likely allows military responders to capture drones and data recorded by the drone or its controller—at least in most cases.
The automobile exception permits appropriately scoped warrantless searches inside vehicles on public roads when there is probable cause the vehicle contains evidence of a crime.
As a threshold matter, drones flying over military installations are, by their very nature, instrumentalities of at least one of the crimes discussed above and would contain evidence of these crimes (e.g. location data demonstrating presence in restricted airspace).
Multiple circuit courts have extended the automobile exception to aircraft because planes, like cars, are extremely mobile and pervasively regulated. This exception has also traditionally allowed searches of closed containers within automobiles, and many older decisions used this to permit searches of electronic data within pagers and GPS devices.
On the other hand, many modern decisions have been less willing to liken physical containers to laptops and personal cell phones. Consumers often use cell phones to operate drones. In Riley and Carpenter, the Supreme Court recognized that private electronic data retains additional protection in contexts that normally would not require a warrant, like a search incident to an arrest.
But professor Adam Gershowitz has convincingly explained why the automobile exception currently allows police to search a car’s on-board computer or infotainment system without a warrant. His arguments apply with even more force to the context of searching data within a drone or its controller, especially the diminished privacy interests in the types of data accessed and the concern about losing access to evidence.
Perhaps a fair summation would be that when data accessed by C-UAS systems looks like traditional “black box” data, GPS information, or sensor data the drone may have illegally collected, the automobile exception would likely allow it.
But if a sophisticated mitigation operation (really a cyber attack) could somehow access text messages, photographs, search histories, call logs, or other personal information about the operator not directly related to the UAS flight, then the automobile exception likely would no longer “fly.”
Can Damage or Destruction Sometimes Be “Unreasonable”?
If force is used to effectuate the seizure of an object, the Fourth Amendment may require that this force be proportional to the threat the object poses or the gravity of the crime it furthers. In other words, there may be an object-seizure version of Tennessee v. Garner.
In Garner, the Supreme Court held that deadly force may not be used to apprehend a fleeing, apparently unarmed suspected felon unless it is necessary to prevent his escape and he poses a significant threat of death or serious physical injury to the apprehending officer or others.
To evaluate whether permanent deprivation of property constitutes a reasonable seizure, a court would likely “balance the nature and quality of the intrusion on the individual’s Fourth Amendment interests against the importance of the governmental interests alleged to justify the intrusion.”
Cases of short drone overflights not endangering lives or property may implicate this analysis. Though surveillance on critical sites could enable attacks or intelligence failures with grave consequences for the nation, these incursions individually only amount to misdemeanors or civil violations. This would at first seem to cut against destroying them.
On the other hand, these are drones, not human lives. And unlike an individual who may be tagged with an arrest warrant actionable by surrounding police forces, once a drone leaves an installation’s airspace, seizing it or locating its operator likely depends entirely on the capabilities of surrounding non-military law enforcement to spot it visually and attempt to triangulate the operator’s location. In other words, “preventing escape” is a much more powerful rationale in the drone context.
Droning On
So much more can be said about this highly dynamic area. Can “mere surveillance” spy drones can be shot down without an “imminent threat”? What can be done to improve interagency coordination? What about intelligence oversight implications and international law issues with respect to foreign drone surveillance? Certainly C-UAS operations on newly-designated “National Defense Areas” could raise numerous legal issues.
Commanders and their legal advisors, while understandably focused on UAS in the context of deployments abroad, must also stay apprised of the c-UAS operating environment at home.
The views presented in this article are those of the author and do not necessarily represent the views, positions, or policies of the Department of Defense, the U.S. Army, or any other agency of the U.S. government.
About the Authors
Hannah Martins Miller is a Major and Judge Advocate in the U.S. Army. She currently serves as the Brigade Judge Advocate for the 3d Mobility Brigade, 101st Airborne Division (Air Assault). She holds an LLM from The Judge Advocate General’s Legal Center and School, a JD from Vanderbilt Law School, and a BA in English from Princeton University.
Ashley Noelle Johnson is a Major and Judge Advocate in the U.S. Air Force, and she holds an LLM from The Judge Advocate General’s Legal Center and School. She received her JD from University of Maryland School of Law, and her BA in Political Science and Philosophy from Spelman College
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The views expressed by guest authors do not necessarily reflect my views or those of the Center on Law, Ethics and National Security, or Duke University. (See also here).
Remember what we like to say on Lawfire®: gather the facts, examine the law, evaluate the arguments – and then decide for yourself!
