Concerns about safety are rising among Hong Kong's diaspora community after authorities in the city arrested a university student under the controversial National Security Law (NSL) when she returned from Japan last month.

The 23-year-old student was arrested over posts she shared on social media, which Hong Kong police described as "inciting Hong Kong independence." The student has reportedly been charged with "inciting secession."

This is the first known arrest of a Hong Konger under the NSL over activities that took place outside of Hong Kong.

Experts and overseas Hong Kong activists say the case shows the city government is trying to expand the jurisdiction of the NSL and create a chilling effect among the diaspora community.

"Authorities in Hong Kong are trying to discipline Hong Kong people living abroad, letting them know that Big Brother is still watching them even when they are in other countries," said Sunny Cheung, an exiled Hong Kong activist and a non-resident fellow at the Pacific Forum.

According to Japanese expert Tomoko Ako, who is familiar with the details of the arrest, the Hong Kong student was not particularly political but was arrested after returning to Hong Kong to renew her identification documents. "The government confiscated her passport and now she can't return to Japan to complete her studies," she told DW, adding that the student was merely expressing her own thoughts on social media while she was in Japan.

Cheung from the Pacific Forum told DW that the case shows Hong Kong's "surveillance network and transnational repression are real."

NSL dampens anti-government movement abroad

Since the NSL came into effect in July 2020, more than 200 people have been arrested under the law and 140 individuals have been charged.

Some political analysts warn about potential risks for Hong Kongers abroad if they decide to return to the city.

"We don't know how the Hong Kong authorities are tracking Hong Kong people's overseas activities or comments, and the latest case would make people who may not view themselves as political very concerned about their own safety," said Patrick Poon, a visiting researcher at the University of Tokyo. "The trend will also affect many families as Hong Kongers abroad now need to think about their own safety when they decide whether it's safe for them to go back to the city or not."

Cheung from the Pacific Forum adds that since the NSL came into effect, the number of people participating in protests organized abroad has declined, and extra measures have been put in place.

"In the US, we organized a closed-door summit involving more than 100 Hong Kongers, and in order to protect participants' safety, we didn't reveal the location of the event. All participants' identities were erased after the event," he told DW.

Cheung also thinks it's important for diaspora communities to try to work with intelligence agencies in different countries, as they can help to counter the Hong Kong government's transnational repression. "In the US, we have been providing some intelligence to the FBI and the practice can be adopted in other countries," he said. "It'll be helpful for diaspora communities in different countries to counter transnational repression."

Foreign governments 'must urge Hong Kong' to revise law

Following the Hong Kong student's arrest, Ako called on the Japanese university to ensure that the student's studies are not interrupted.

"She wants to continue her studies, so I've requested her university to help her continue her education through online courses," she told DW.

And while the Japanese government usually doesn't help foreign residents who are arrested outside of Japan, Poon from the University of Tokyo thinks it's important for governments to express their concerns about arrests or detentions under the NSL.

"We all believe host countries should raise concernsto the Hong Kong government, telling them that a particular individual is a legal resident of their countries… The Hong Kong government should return the individual's passport to her or him unless the person has been formally charged," he told DW.

He stressed that the international community must urge Hong Kong authorities to amend the NSL, and ensure it is aligned with the standards laid out by international conventions that Hong Kong has signed up to.

"Since the NSL is ambiguous, the international community should push Hong Kong authorities to revise the law and make it clearer," he said, adding that as long as Hong Kong hasn't withdrawn its signature on the international covenant on civil and political rights, authorities in the city are expected to follow the international norm.

Edited by: Sou-Jie van Brunnersum