Paul Stephan on “Spy Balloons and Their Ilk: International Law and the Battle for Near Space”

I’m very pleased to tell you that today’s guest post is by Professor Paul Stephan of the University of Virginia School of Law, and as you’ll soon see, he is an authentically fresh thinker. He expertly unpacks the law related to sovereignty as applied to the balloon controversy, and devises a very thoughtful–and rather provocative–approach to avoiding the potential for “strategic blunders” in the future.  He says:

Put simply, if deploying surveillance balloons would benefit the United States, and the costs associated with adversary balloon surveillance are tolerable, our country might opt for a regime where states presumptively waive the power given them by the principle of sovereignty to destroy adversary spy balloons in near space.

This tacit consent would not extend to spaces used by civil aviation, and could be withdrawn without notice. Appropriately limited, a permissive norm might enable the United States and its adversaries to avoid strategic blunders without sacrificing too much of the interests that the principle of sovereignty promotes.

Obviously, there is much food for thought here.  BTW, Professor Stephan has a new book out, The World Crisis and International Law, which I’ve bought and put high in my reading queue.  The scholarship and innovative thinking in his essay below makes me very much look forward to reading more of his ideas!

Spy Balloons and Their Ilk: International Law and the Battle for Near Space

Paul B. Stephan, University of Virginia School of Law

      The detection, surveillance, and destruction of a balloon originating in China  and overflying U.S. territory has triggered much excitement and commentary. The United States maintains that the balloon was on a spy mission to collect either images or signal intelligence; China asserts that this was a weather balloon that blew off course. Press reports say that it stayed around 60,000 feet (18.3 kilometers), well above altitudes attainable by civilian aircraft but within the range of specialized military aircraft. This area is commonly called near space.

      The United States was within its legal rights to shoot down the balloon. Was it wise to do so? Can we imagine behavior that violates sovereignty but nonetheless is tolerated based on a principle of tacit consent?

      Some law applies, but open questions abound. At a certain altitude, the 1967 Outer Space Treaty kicks in, which generally protects objects from attack. It bans claims of national sovereignty in outer space, which it declares the province of all “mankind” (today we would say “humanity,” but the past is another country).

     Notably, however, neither the treaty nor any other international instrument specifies where outer space begins, and thus where the Treaty applies. Some scientists have proposed a boundary for outer space, called the Kármán line, at 330,000 feet (100 kilometers).

    This limit, though, has no force of law and seems based on mathematical elegance as much as physics. We can assume that the spy satellites that the great powers use for images and signal intelligence come within that treaty’s ambit and thus, in the absence of an armed conflict, enjoy protection from attack. But it’s implausible that the balloon fell within the treaty’s penumbra.

      Several treaties, including the 1944 Chicago Convention and its later protocols, lay out the rights and duties of states concerning international civilian aviation. They confirm the fundamental right of a state to control its airspace and the duty to protect civilian aircraft. They do not preclude destroying overflying aircraft, providing a state takes some care to minimize loss of life or harm on the ground.

      In the case of military aircraft engaged in deliberate overflights for purposes of espionage, we have state practice: international law recognizes a right to disable the aircraft, even at the risk of killing the crew. But again we don’t know how high up airspace goes. The Soviet Union’s 1960 shootdown of Gary Power’s U-2 mission occurred at 70,000 feet (21.3 kilometers). There was no Outer Space Treaty then, but the United States did not claim that the attack was unlawful. Rather, like China this month, it denied that the mission involved espionage, claiming that it was an innocent weather plane off course.

      Civilian aircraft typically have a ceiling of roughly 50,000 feet (15 kilometers). Military aircraft can go higher: the Financial Times reports that the current air-breathing craft record is 90,000 feet (27.4 kilometers). The balloon incident involved likely intelligence gathering at an altitude that posed no real risk to civilian aviation but does not qualify as outer space. What law governs near space, adjacent to but not yet outer space?

      The international legal principle of sovereignty applies up to the point where the Outer Space Treaty kicks in, even though no one knows precisely where to draw that line. This principle, however, does not prescribe bright-line rights and duties. Sovereignty does not forbid actions by other states so much as offering a justification for measures taken in its defense. Destructive actions used in defense of sovereignty still must satisfy the law of armed force, including not targeting civilian objects, using only proportionate force, and seeking to avoid collateral damage to civilian objects.

      Further complicating the story is the generally accepted principle that international law does not forbid espionage as such but does recognize the ability of states to take measures authorized by their domestic law to deter this activity.

     Anti-espionage measures are not so much an inherent right of states, but rather a facet of the principle of sovereignty. International law allows states to treat aircraft engaged in espionage as military rather than civilian objects, even if operated by civilians rather than members of armed forces. The legal motivation for the claims made by the Eisenhower and Xi administrations that the downed craft were doing weather research is that civilian craft are not legitimate targets for a forcible response, but military ones are.

      The military-civilian distinction has a fraught history. The Soviet Union, and later Russia, justified the 1983 destruction of KAL 007 because it appeared in real time to be on an espionage mission, even though the aircraft itself was one associated with civilian aviation.

     Most observers regard the Soviet attack as unreasonable and therefore unlawful, even if some evidence of spying was detectable, because the preponderance of evidence at the time of the attack indicated it was a civilian object. In 1987, Soviet military aircraft tailed Matheus Rust but did not shoot him down, even allowing him to land in Red Square, apparently because his conspicuous flight path and small civilian plane seemed far removed from any possible spy mission.

      It seems reasonably clear that the Biden administration acted legally when it ordered the destruction of the Chinese balloon. The balloon found its way into U.S. airspace, flew too low to enjoy the protection of the Outer Space Treaty, and, given its size and cargo load, plausibly seemed to be engaged in espionage rather than civilian scientific research.

     Based on observations of the craft, the government had a high level of confidence that no humans were present, eliminating the risk of killing civilians. China did not claim that the United States acted unlawfully, but rather that the attack was rude. The shoot-down, China’s Foreign Ministry said, was a clear overreaction and a serious violation of international practice,” not of international law. Does China have a point?

      What should be the norm when a state detects an unoccupied object spying at an altitude that poses no risk to civilian aviation but too low to enjoy the protection from armed attack bestowed by the Outer Space Treaty? Should a state follow an automatic shoot-down policy for any presumed military object that enters this range of its airspace without permission?

     Until this incident, press reports indicate, the U.S. military made no serious effort to detect and disable such craft, even though the intelligence community, apparently retrospectively, had discovered their presence. Was this negligence or prudence?

      First, I will speculate why a state that has spy satellites might use a high-altitude balloon for espionage. A necessary disclaimer: I never encountered this technology during my times in government; this is all guesswork based on a general familiarity with the intelligence world, not on any classified material.

     Satellites orbit in an easily observed pattern; changes in orbit are possible but reduce the useful life of the craft. Predictability invites countermeasures. The target state can thwart imaging with cover, camouflage, or concealment; it can block signal collection by going silent or using masking technologies. All the target needs to know is when the satellite will be overhead, which is not hard to determine.

      Balloons, even if maneuverable (as the Chinese craft apparently was), depend mostly on wind to determine where they go, gaining an element of surprise. With the right mix of guidance and luck, a balloon can end up over a target without enough time to take countermeasures. Balloon-based intelligence gathering thus can supplement satellite reconnaissance.

      Second, I consider whether surprise surveillance is bad or good. A target state in principle should wish to deny its adversary any advantage while pushing its own intelligence-gathering as far as it can go. The U.S. government denies that our country uses this technology. I neither take the Chinese at their word that the United States has such a program nor reject outright our government’s assertion that we don’t. If we have this capacity, the government probably should pretend that it doesn’t at least until caught out.

     Any public acknowledgement that we might make would help our adversaries’ intelligence communities to press their political masters for more resources to respond. It remains possible to hypothesize, without any proof one way or the other, that both the United States and China either use balloons to supplement satellite espionage or have the capacity to do so.

      If symmetrical capacities exist, is the United States better off trying to track down and destroy Chinese balloons as often as possible, or should it take more of a laissez-faire approach? The answer depends on how one assesses the costs and benefits of espionage. On the one hand, the United States invests a lot of money in protecting its secrets. Sometimes the secrets involve breakthrough technological capacities that our adversaries lack but want: think of the atomic spies and what they did for the Soviet Union.

     Sometimes the secrets involve sources and methods which, if compromised, would deny the United States valuable information: some press accounts attribute the loss of many U.S. agents in China to the compromise of the technology they used to communicate with their handlers. And some secrets involve the deployment of our known military and intelligence capacities, which if revealed will enable our adversaries to take better countermeasures. Balloon programs seem to fall in this last category.

      On the other hand, espionage has enormous benefits. It provides insight into an adversary’s intentions and capabilities. Perhaps most importantly, it prevents policymakers who determine how to deploy our awesome strategic capacities from making mistakes. It reduces both types of errors, those that involve believing in threats that do not exist and ignoring those that do.

      In the case of spy satellites, the United States and its adversaries have arrived at a fairly permissive equilibrium based on law. The Outer Space Treaty largely protects the satellites from attack, excepting perhaps in an ongoing armed conflict. It says nothing about, and therefore implicitly permits, countermeasures at the targeted point, such as concealment and silence. Jamming of communications between an adversary’s satellite and its earthbound controllers present some interesting and not wholly resolved legal questions, but as best one can tell this does not happen very often and a tacit norm against such jamming may exist.

      Even if the Outer Space Treaty does not apply to balloon surveillance in near space, perhaps a similar approach, based on tacit consent rather than formal legal obligation, might apply. This suggestion rests on two assumption, neither of which I know to be true but both of which seem plausible. Assumption 1: the United State either has a balloon spying program similar to the Chinese or could easily implement one. Assumption 2: the intelligence costs and benefits of such a program would extend those associated with surveillance satellites, with benefits exceeding costs.

     Put simply, if deploying surveillance balloons would benefit the United States, and the costs associated with adversary balloon surveillance are tolerable, our country might opt for a regime where states presumptively waive the power given them by the principle of sovereignty to destroy adversary spy balloons in near space.

     This tacit consent would not extend to spaces used by civil aviation, and could be withdrawn without notice. Appropriately limited, a permissive norm might enable the United States and its adversaries to avoid strategic blunders without sacrificing too much of the interests that the principle of sovereignty promotes.

      I have written in several places, including my new book, The World Crisis and International Law, about the need to devise approaches to international lawmaking in the face of the deep domestic and international divisions that make new treaties and the empowerment of international organizations effectively impossible. The spy balloon conundrum provides a useful example.

     At this fraught moment, neither China nor the United States can allow its domestic audiences to see it as soft on the other. Tacit cooperation is the only way ahead, if cooperation otherwise seems desirable.

      Operating against the background principle of sovereignty in near space, states might tolerate overflights by such craft, thus enabling reciprocal collection of better and useful intelligence. Informal cooperation allows for learning by doing, letting the interested parties display their preferences (or not) for cooperation and reliability.  The balloon episode might yet contribute to national security by reducing unnecessary flash points and pointing toward useful solutions to problems of mutual concern.

About the author:

Paul B. Stephan is the John C. Jeffries, Jr., Distinguished Professor of Law and the David H. Ibbeken ’71 Research Professor of Law, as well as Senior Fellow of the Miller Center of Public Affairs, at the University of Virginia. He served as Counselor on International Law to the State Department’s Legal Adviser in 2006-07 and Special Counsel to the Defense Department’s General Counsel in 2020-21.

The views expressed by guest authors also do not necessarily reflect the views 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!

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