The alleged Taiwanese ringleader of a big telecoms fraud syndicate was all set to be extradited from Poland to China last month - a coup for Beijing's international policing operations and its extensive efforts to hunt down fugitives.

Hung Tao Liu's handover would have been a breakthrough in a probe that three years ago saw nearly 100 Taiwanese suspects taken into custody in Spain, flown to Beijing and then escorted from the plane between uniformed Chinese officers. Instead, his case is likely to become a major setback and an embarrassing failure for Chinese authorities.

The European Court of Human Rights ruled in October that Liu should not be turned over to Chinese authorities because they had failed to sufficiently guarantee that he would not face ill-treatment on arrival. That judgment will make extraditions from the continent to China significantly more difficult, if not near-impossible, according to lawyers, human rights activists and legal scholars. The Madrid-based nongovernmental organization Safeguard Defenders called it a "momentous decision" to protect human rights in Europe.

The ruling undercuts a decade-long effort by Beijing to normalize the repatriation of suspects wanted under Chinese law. But it is also signals a growing wariness of Chinese security operations on the continent. Multiple governments have launched investigations in recent weeks after the discovery of Chinese police "service stations" in dozens of cities from Dublin to Milan, reviving debates about whether China and Europe can agree on basic law enforcement protocols.

The court reflects "a shifting view in Europe in terms of rule of law and rights protection in China's legal and criminal justice system," said analyst Katja Drinhausen of the Mercator Institute for China Studies in Berlin.

This comes at a time when the European Union is rethinking its relationship with China. In recent years, ties have frayed over human rights issues, particularly in Xinjiang and Hong Kong. Russia's full-scale invasion of Ukraine - which China has yet to condemn - offered a stark reminder of the risks should engaging an authoritarian regime fail.

Miriam Lexmann, a member of the European Parliament from Slovakia, said Europe needs to heed the lessons of the invasion and reevaluate how it works with China, including on legal issues. "We have to rethink extradition treaties and any kind of cooperation with China," said Lexmann, whom China sanctioned last year in retaliation for E.U. restrictions on Chinese officials over mass incarceration in Xinjiang.

The court's unanimous decision on Liu's treatment drew heavily on research from human rights groups and notes China's refusal to allow visits from representatives of international organizations who might, for instance, inspect detention facilities. This opacity is cited as a key reason the court cannot take China's informal guarantees at face value.

The accused's citizenship was not relevant to the ruling because it does not touch on issues of sovereignty, according to Yu-Jie Chen, an assistant research professor at the jurisprudence institute of Academia Sinica in Taiwan. "It is really just discussing whether this Taiwanese, as a person like everyone else, can be extradited to China," she said.

Unless the decision is appealed, it will apply to any extradition sought by China from a European country. Lawyers say it is unlikely to be overturned. Liu, who is in his early 40s, remains in custody in Poland.

"This ruling is actually very simple," said Marcin Górski, a legal scholar at the University of Łódź in Poland who represented Liu. "If you are suspected of applying torture and if you close your country to international scrutiny, this is the outcome, because we do not extradite people from Europe unless we are pretty much sure that they wouldn't be killed or tortured."

Lawyers involved in ongoing extradition hearings expect the judgment to undermine ongoing and future proceedings, in part because the court addressed in such general terms the concerns of mistreatment in Chinese detention.

Enrico Di Fiorino, an Italian lawyer who has worked on extradition cases, said the ruling also was significant because the suspect is not political or part of a religious group. "What is requested to change is - at the end of the day - the Chinese legal and judicial system, to avoid the use of torture and other forms of ill-treatment in its detention facilities and penitentiaries," he said.

The investigations launched recently into the existence of those Chinese police "service stations" - believed to operate in at least 50 locations worldwide, according to a recent report by Safeguard Defenders - center on a separate legal concern. Yet both issues highlight the challenges that China's transnational policing tactics pose for democratic countries.

"China is acting as if they could implement their own sovereignty on our soils," said Reinhard Bütikofer, a member of the European Parliament from Germany, who was also sanctioned by Beijing. "It really speaks to the necessity to step up European self-defense against Chinese exportation of oppression."

Bütikofer's calls for E.U. member states to suspend existing extradition treaties with China have largely gone unheeded, but he believes that leader Xi Jinping's harsh political repression and his recently extended authority at the Chinese Communist Party's congress could "resuscitate that conversation."

Chinese Foreign Ministry spokesperson Zhao Lijian on Wednesday denied allegations that China is running illegal police stations, saying the service centers were run by volunteers from the overseas Chinese community to carry out processes such as renewing driving licenses. "They are not police personnel from China. There is no need to make people nervous about this," he said during a regular news briefing in Beijing.

Neither China's Ministry of Public Security or its National Supervisory Commission responded to requests for comment.

A high-profile, global anti-corruption campaign called Sky Net has been the driving force of China's international policing efforts. The operation brings together law enforcement, anti-graft watchdogs, diplomats and judicial departments to hunt down fugitives. Since 2017, Sky Net has been responsible for more than 7,000 individuals being returned to China to stand trial, the party's anti-graft watchdog said last month.

In addition to extradition treaties and Interpol red notices, Chinese authorities also rely on informal measures to "persuade" suspects to come back to China. Fox Hunt, a narrower campaign, focuses primarily on people wanted for economic crimes.

At an Oct. 24 news conference in Washington to announce charges against Chinese intelligence officers and officials in three separate cases, FBI Director Christopher A. Wray said that the individuals involved had "mercilessly harassed a naturalized U.S. citizen to try to force him to return to China against his will" as part of a Fox Hunt probe.

Pushback against Chinese methods and the Liu judgment should make extraditions to China more difficult, but it remains unclear how much separate governments will respect the European Court of Human Rights judgment, noted Eva Pils, an expert on Chinese law at King's College London.

There's also concern whether China will respond to official channels being blocked by doubling down on off-books methods, Pils said, "where agents of the Chinese state carry out what they see as a kind of law enforcement activity, but without permission."

Ellen Nakashima in Washington and Pei-Lin Wu in Taipei contributed to this report.

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