HONG KONG — Jimmy Lai, the publishing tycoon and one of Hong Kong’s most outspoken critics of the Chinese Communist Party, was charged under the city’s new national security law on Friday, as Beijing intensified its efforts to smother pro-democracy activism in the once-freewheeling metropolis.
The move against Mr. Lai was not surprising. He is one of the best-known faces internationally of Hong Kong’s pro-democracy movement, and Chinese state news outlets have long railed against him as one of the driving forces behind the huge anti-government protests last year.
Still, the news underscored Beijing’s determination to intimidate an already disheartened movement. Street protests have mostly evaporated since the law was enacted in June, and open dissent among most residents has quieted. But well-known activists such as Mr. Lai have continued to speak out, to the fury of Chinese officials.
“Beijing wants to get to the bottom of this problem, and it seems they are not yet satisfied that they have achieved the purpose of keeping Hong Kong people quiet,” said Willy Lam, a professor of Chinese politics at the Chinese University of Hong Kong.
By charging Mr. Lai, Professor Lam said, “they are definitely pulling out all the stops to stifle the voices of opposition.”
Mr. Lai’s indictment followed a string of other punishments of high-profile figures in recent weeks, including the sentencing of the young activists Joshua Wong and Agnes Chow, and the ejection of several pro-democracy lawmakers from the city’s legislature, which led the rest of the opposition to resign en masse.
In targeting Mr. Lai, the Chinese government may also have been sending a message to other countries that have been harshly critical of its crackdown on Hong Kong.
If convicted, Mr. Lai could face up to life in prison. Under the national security law, court proceedings can be held behind closed doors, and defendants can even be removed to mainland China to stand trial.
Mr. Lai, 73, has long enraged the Chinese authorities. As the founder of Apple Daily, a gleefully anti-Beijing tabloid that is one of the last remaining such publications in Hong Kong, Mr. Lai has infused the pro-democracy movement with money and positive publicity.
Last year, he traveled to the United States to meet officials including Vice President Mike Pence and Secretary of State Mike Pompeo, lobbying for action against China. He has also called for sanctions on Chinese officials.
As a result, Chinese officials have directly denounced him, and state-controlled newspapers labeled him the “black hand” behind last year’s protests, which posed the most serious challenge in decades to Beijing’s rule over the territory.
“By openly colluding with external forces to endanger national security, Jimmy Lai and a small handful of other anti-China troublemakers in Hong Kong have purposely undermined Hong Kong’s prosperity and stability and its citizens’ fundamental well-being,” a spokesman for the Chinese foreign ministry’s commissioner in Hong Kong said in a statement in August.
Mr. Lai was arrested in August on suspicion of violating the security law, which the central government had bypassed the Hong Kong legislature to impose on the semiautonomous territory. That same day, police officers raided Apple Daily’s headquarters.
The police did not say specifically what Mr. Lai had done to violate the security law. As written, the law is not supposed to be retroactive. Since it was imposed, Mr. Lai has said that he would be more careful about his words and actions, warning that even speech could be taken as evidence of collusion.
Indeed, many worried that the prosecution of Mr. Lai proved that China was eroding the freedom of expression that distinguishes Hong Kong from the mainland. Chinese officials have insisted that the security law would apply only in limited circumstances and to a small number of people.
Claudia Mo, a former pro-democracy lawmaker, said the authorities might have been looking for a way to shut down Apple Daily, which has continued to needle the government even after the security law was enacted.
“This seems likely a key part of their ideological control over Hong Kong,” said Ms. Mo, who was among the mass resignations from the legislature last month. “They hate Lai’s high political profile and find his media influence more than bothersome.”
The lack of clarity over what, exactly, Mr. Lai had supposedly done to run afoul of the law would further cloud the already-murky media landscape in the city, said Keith Richburg, the director of the University of Hong Kong’s journalism center.
“It would be very helpful for us if they spelled out exactly what is allowed and not allowed and what constitutes foreign collusion,” Mr. Richburg said, adding that journalists conducting interviews might now worry that they could be charged, too. “But these are all things that we’re going to have to figure out, because they’re not going to deign to tell us.”
Mr. Lai was already in jail after being denied bail on unrelated fraud charges, a decision he is appealing. But because of the charge under the national security law, which grants the authorities sweeping powers to hold defendants without bail, it is unlikely that he will win release.
The law also shifts the legal landscape for Mr. Lai. Defendants can be tried in mainland China, where the legal system is significantly more opaque than in Hong Kong.
Even if Mr. Lai is tried in Hong Kong, the security law empowers the city’s chief executive, who is selected by Beijing, to appoint special judges, and the trial can be held behind closed doors.
More than two dozen others have been arrested under the measure. Tony Chung, 19, an activist who was also charged under the law, was convicted on Friday of desecrating the Chinese national flag and participating in an unlawful assembly last year. A separate trial on charges under the national security law trial is pending.