A group of California plaintiffs has filed a lawsuit against Chinese tech giant Tencent in state court, alleging that the company’s WeChat mobile app has censored and surveilled them and shared their data with Chinese authorities.

The lawsuit, which seeks class-action status, claims that the company’s practices violate the plaintiffs’ free-speech and privacy rights and “unjustly enrich Tencent at the expense of California WeChat users.”

The case is another sign of the mounting scrutiny of WeChat, a popular communication tool in China that is also used by millions of Mandarin speakers around the globe. The Trump administration tried to ban the app in the fall, saying it posed threats to national security because it collects “vast swaths” of data on users and offers the Chinese Communist Party an avenue for censoring or distorting information. A federal court issued a preliminary injunction halting that ban, in response to a separate lawsuit saying the ban would harm plaintiffs’ First Amendment rights.

In the latest lawsuit, filed in the Superior Court of California in Santa Clara County, the plaintiffs seek court injunctions to halt Tencent’s alleged actions and ask that the company be ordered to pay damages to compensate them for financial loss, emotional trauma and psychological stress. Tencent subsidiaries in the United States and Singapore are named as the defendants.

Tencent’s behavior “chills constitutionally protected speech,” the plaintiffs, including six anonymous California residents and the nonprofit group Citizen Power Initiatives for China (CPIFC), wrote in the lawsuit. “Indeed, many WeChat users have told CPIFC that they feel real fear that the Party-state or its agents will retaliate against them or their family, and that, as a result, they self-censor — despite the fact that they live in California.”

Tencent declined to comment on the lawsuit, pointing to past remarks the company has made about its WeChat operations, including that Tencent “operates in a complex regulatory environment, both in China and elsewhere,” and complies “with local laws and regulations in the markets where we operate.”

Tencent is a large global company, with annual revenue of more than $50 billion. It is the world’s biggest online gaming company, with large ownership stakes in U.S. companies such as Epic Games. Last year, it led a consortium that bought 10 percent of Universal Music Group.

The lead counsel for the plaintiffs, Times Wang of North River Law in D.C., said most of his clients had requested anonymity in the lawsuit because they fear retaliation by Chinese authorities or others. The complaint refers to them as “Doe Plaintiffs 1-6” and describes them as a mix of U.S. and Chinese citizens with professions including a translator, an entrepreneur and an installer of home security systems.

The seventh plaintiff, CPIFC, helped organize the lawsuit after spending nearly a year interviewing WeChat users in the United States. Yang Jianli, a Chinese dissident and founder of the group, said in an interview that CPIFC, which aims to promote a transition to democracy in China, started thinking about a lawsuit after hearing frequent complaints from WeChat users in China and the United States that they were being censored or locked out of their accounts after expressing criticism of China.

Yang said he views the lawsuit as a more effective way to counter Tencent than the Trump administration’s proposed ban, which he said could be difficult to pull off under U.S. law.

Wang, the son of Chinese political prisoner Wang Bingzhang, specializes in legal cases involving human rights in China. Also representing the plaintiffs are civil rights lawyer Paul L. Hoffman and half a dozen lawyers from the Lanier Law Firm in Houston, including Kenneth W. Starr, independent counsel during the impeachment of President Bill Clinton.

Among other things, the lawsuit alleges that Tencent has turned over California WeChat users’ data and communications to Chinese authorities, censored and surveilled WeChat users in the state, suspended and blocked their accounts after they have posted material critical of China, and profited by using their data and communications to improve the company’s censorship and surveillance algorithms.

As on Facebook, WeChat users can send direct messages, chat in groups or post updates on their timelines. One plaintiff, who created a WeChat account using his U.S. phone number, said Tencent suspended his account after he posted “politically sensitive information.” Later, he was able to read other people’s timeline posts but was not able to post updates of his own.

WeChat also repeatedly shut down a chat group he helped set up with his fellow Chinese university alumni, the plaintiff said. One of his classmates, still living in China, said security agents there summoned him to discuss the group’s activities and asked him about the group’s overseas members, the lawsuit says.

Another plaintiff, who works as a massage therapist, said his account was suspended for 42 days in early 2020 after he posted messages about the coronavirus pandemic. As a result he was unable to communicate with clients and lost about $500 a day in business, he said. A third plaintiff, who runs a jewelry business, said that after she made political comments on WeChat, she was locked out of a group she created to discuss jewelry with clients, causing her to lose business.

Plaintiff No. 4 said some of her posts have prompted Tencent to send her warnings that “continued posting will lead to adverse actions being taken against her account.” For example, in 2020 “she received warnings against posting and forwarding content relating to the coronavirus pandemic,” the lawsuit says. And several of the chat groups to which she belongs have been suspended by WeChat “because of their content, which Tencent monitors, censors, and surveils,” the lawsuit says.

Plaintiff No. 6 said he created a WeChat account using a U.S. phone number “because his understanding was that doing so would avoid censorship and surveillance. Yet, to his chagrin, that wasn’t true,” the lawsuit alleges. After posting “anti-CCP content,” his account has been suspended several times. And although it is currently unblocked, his friends and family in China cannot see his posts or messages. “No notice was given to Doe Plaintiff 6 that his account was being treated this way,” the lawsuit says.

The plaintiffs’ allegations are similar to those that WeChat users in North America shared with The Washington Post recently. Those users, too, complained of being censored and locked out of their U.S.-registered accounts after posting information critical of China.

The lawsuit also cites research published last year by the University of Toronto’s Citizen Lab showing that WeChat was subjecting overseas accounts to surveillance to train algorithms used to censor information in China.

“We show that files and images shared by WeChat users with accounts outside of China are subject to political surveillance, and this content is used to train and build up the censorship system that WeChat uses to censor China-registered users,” the Citizen Lab researchers wrote.

Asked about that report in December, Tencent spokesman Sean Durkin said: “With regard to the suggestion that we engage in content surveillance of international users, we can confirm that all content shared among international users of WeChat is private.”

Chinese authorities require Tencent to heavily censor the app inside China. Posts about Chinese politics — and many other topics — disappear when they are sent to or from a China-registered account. Chinese authorities have used the app to monitor political dissidents and other critics, some of whom have been detained by police or sentenced to prison for their communications.

That censorship is not limited to China, however. If a Chinese student or worker moves abroad and continues using an account created in China, the censorship will remain, according to Jeffrey Knockel, a research associate at the Citizen Lab, which studies information technology and human rights.

Durkin confirmed that an account created in China will always be treated as a Chinese account, even if the user moves abroad and accesses it from an overseas device. He said the company considers accounts created inside and outside China to be “separate but interoperable” and subject to “different regulatory environments.”

Yet users who created their accounts in the United States also complain of censorship and inexplicably blocked accounts. Wang, the plaintiffs’ attorney, said all users in the United States should be free from censorship.

“We’re saying it should be where you physically are that matters,” he said.