At talks in Sochi, Russian President Vladimir Putin backs his Belarusian counterpart over forced landing of Ryanair jet.

On Sunday, Ryanair Flight 4978 was traveling over Belarussian airspace from Athens to Vilnius when Minsk air-traffic control delivered alarming news. “You have bomb on board,” the controller said. “We recommend you to land.” A Belarussian MiG fighter jet showed up on Ryanair’s wing to emphasize the recommendation. Minutes later, the Ryanair plane landed, and Belarussian authorities arrested two passengers: Roman Protasevich, a Belarussian dissident, and his Russian girlfriend, Sofia Sapega. The rest continued on to Vilnius, except for a handful who preferred to stay in Minsk, possibly to sightsee, possibly because they were Belarussian operatives planted on the flight to supervise the arrest.

Ryanair’s CEO called the incident “state-sponsored hijacking.” It was not. Technically, you have to be on a plane to hijack it. But the Ryanair incident was nevertheless diabolical—and what makes it particularly diabolical is that Belarus may have managed to pull it off without violating its agreements under international law.

[Anne Applebaum: Other regimes will hijack planes too]

Of course the bomb threat was a trick. Belarus claims that Hamas emailed to inform Minsk National Airport that it intended to bomb a flight if the European Union did not “abandon its support for Israel in its war” in Gaza. Hamas’s purported email specifically noted the intention to kill participants in the Delphi Economic Forum, a Davos-like public-policy event in Athens. I was one of the speakers. Most of the foreigners appeared remotely, and the few who appeared in person, including myself, flew home when the forum concluded more than a week before the Belarus incident. The Ryanair flight may have carried a few stragglers, but to plant a bomb a week later would be like trying to pull off a Christmas attack on January 2. The Daily Beast and Newlines noted another inconsistency: The bomb threat arrived 24 minutes after the Minsk control tower radioed to the Ryanair flight crew.

If Hamas and Belarus have invented clairvoyance and time travel, the national security implications for the United States and others will be considerable. Even in the absence of such developments, however, the world has changed in disturbing ways. Flying over a foreign country has, until now, felt to most people like teleporting past it—as if remaining tens of thousands of feet above hostile territory, we are not in some important sense in it, and vulnerable to being forced down and arrested. In the future, if the Belarus ruse is allowed to stand, the experience will come to resemble taking a train, with all the terrestrial legal risk that entails.

John Byerly retired after 30 years at the State Department, where he served as an aviation lawyer and principal aviation negotiator. He told me that Belarus’s main legal obligations come from the 1944 agreement known as the Chicago Convention on International Civil Aviation. He said Belarus had acted outrageously but perhaps not illegally. First, the Chicago Convention reserves, under its very first article, territorial sovereignty to the country that is being flown over. That sovereignty includes the right to order the landing of a plane in its airspace. Chicago does not say that countries can force a landing only under certain enumerated circumstances. It’s simply one of their rights.

“Could they force a flight to land because the Belarussian minister of transportation found out Justin Bieber was a passenger, and wanted his autograph?” I asked Byerly. He said that request would be unreasonable and abusive—but emphatically not contrary to the text of Chicago.

[Read: The west is failing Belarus]

The Chicago Convention does limit the means Belarus could use to force a landing. Byerly pointed to Article 3bis, which outlaws the “use of weapons” against civilian aircraft, and although it clearly lets states intercept airplanes, “the safety of aircraft must not be endangered.” (Article 3bis was added to the convention after the Soviet Union shot down Korean Air Lines Flight 007, which in 1983 had strayed into Soviet airspace and was mistaken for a U.S. spy plane; 269 people were killed.)

“If the MiG had fired its weapons against the Ryanair flight, that would have been unlawful, irrespective of whether they hit or missed,” Byerly said. But because the fighter jet did not fire—not even a warning shot, like the ones that went unheeded before the Korean airliner was brought down—Belarus could argue that it exercised its rights of sovereignty and abided by Article 3bis. Calling in a fake bomb threat may not even be illegal, unless doing so endangers the aircraft. The plane landed safely. The MiG was but a friendly escort for the Ryanair crew and passengers, ready to blast out of the sky any migratory birds that might impede their descent.

Moreover, when I spoke with Olga Koloschich, a Belarussian aviation lawyer and adviser to the country’s state-owned air services, she implored me to notice the wording of the air-traffic controllers’ instruction to the crew. We recommend you to land. “The captain of the Ryanair aircraft made the decision to land at Minsk National Airport on his own,” she said. The controllers advised the captain that his plane might be carrying a bomb—but they then left him the option of landing, according to their advice, or continuing to fly and taking his chance with a plane that might explode at any moment.

Russian and Belarussian authorities stress that the United States has forced down planes too. Some of the comparisons make less sense than others. In 2013, Bolivian President Evo Morales flew from Moscow and was forced to land in Vienna, to ensure that Edward Snowden was not a passenger on his presidential jet. But he was aboard a state aircraft, not a civil one, so the Chicago Convention did not apply, and Austria could demand that he land for any reason. (After a Snowden check came back negative, Morales was allowed to proceed.)

A more dramatic event involved the Palestinian terrorists who hijacked the Achille Lauro cruise ship, murdered an elderly American Jew, and dumped his corpse into the sea in 1985. After the attack, the Egyptian government chartered an Egyptair 737 to ferry the hijackers to safety in Tunis. The United States intercepted the 737 over the Mediterranean Sea and threatened to shoot it down if it did not land at a NATO base in Sicily. Here the comparison is a little closer to the Ryanair case: Egyptair is a civilian airline like any other. But the United States argued that the jet had been chartered by the government, for a government task, and had carried only four terrorists and 10 Egyptian soldiers—so it was not a civilian flight but a government one, and the United States could intercept it and force a landing. By contrast, you or I could have boarded Ryanair 4978. (Tickets were only 19.99 euros, if bought far enough in advance.)

A slightly more relevant example is the 2003 forced landing of the private jet of Andrey Vavilov, a Russian politician, in California, so that he could be questioned by prosecutors. That was a civil aircraft, even though you or I could not have boarded it. What distinguishes that case from the Belarussian one is that prosecutors did not confect a fake bomb threat, and they did not terrify or endanger 130 other people.

In bizarre incidents such as last weekend’s, Byerly said, policy makers often look for something illegal and fail to find it. “It would simplify their work,” he said. “But often the difference is not one of aviation law.” The scandal happens legally, in plain sight. That is why the European Union and others are scrambling: They have to find a punishment suitable for a country that has twisted the rules but may not have broken them. That could include boxing off Belarussian airspace. Whatever revenue tiny Belarus expected to get from overflight fees will drop, as carriers prefer to skirt its border. Belavia, the Belarussian airline, is losing its permit to fly to Europe. (Russia, Belarus’s ally and patron, has responded by barring European flights that avoid Belarus.)

But Belarus got its man. And other countries will wonder whether they can pull off a similar stunt—and maybe not only with their own exiled citizens. Russia is a big country, and many flights pass through its airspace. The Belarus ruse leaves little doubt that President Vladimir Putin could effortlessly concoct an excuse to ground a plane carrying the Americans he considers enemies. These could include former U.S. Ambassador Michael McFaul, former National Security Adviser John Bolton, or the Putin critic Bill Browder, should they be foolish enough to fly from (say) New York to Delhi, or Los Angeles to Singapore, without making sure their flight path doesn’t cross Siberia or graze the Russian Far East. Byerly noted that passenger-name data are shared with overflight countries. Russia, China, or Iran could just wait for a McFaul, a Guo Wengui, or a Salman Rushdie to pop up, then click send on a hastily written bullshit email from the Asian Dawn Movement, the New Provo Front, or some other terrorist group of their choice. While the plane is on the ground, why not scan everyone’s passport, like a random sobriety check on the highway? Maybe they’d get lucky.

The passport-check scenario, minus the email, could already happen. Planes make unscheduled stops all the time, for mundane reasons including mechanical woes. Those stops can end badly now—and they surely would if any of those named above were stopped in the wrong country, even for innocent reasons. (Think of the famous “Marge vs. the Monorail” episode of The Simpsons, in which the villain’s getaway flight to Tahiti stops unexpectedly in a town he defrauded before Springfield, and angry locals raid the plane.) No Belarussian dissident would risk transiting the country by train—on a strange journey, say, from Milan to Minsk, en route to Vilnius. But flying induces a kind of hypnosis, a delusion of security.

What happened to Roman Protasevich and his girlfriend punctured that delusion, revealing that norms—not laws—have prevented even the mischievous countries above from forcing involuntary layovers rather than waiting for them to happen. That is one more reason why Belarus’s devilish gambit should lead to stiff punishment: The law is little protection, so if norms go, there won’t be anything left. When I book a flight in the future, I would prefer to worry only about cheap tickets and frequent-flyer status, and not also about the stack of navigational charts that might determine whether my next trip will be one-way, to a dungeon in some despotic hellhole.

Belarus's authoritarian leader will travel to Sochi to meet the Russian president.