HONG KONG (AP) — A Hong Kong court started hearing the final arguments Wednesday of some of the city’s best-known pro-democracy activists tried under a law imposed by China’s ruling Communist Party to crush dissent.

The activists’ subversion trial is the biggest prosecution yet under such law. They may face up to life in prison if convicted.

The defendants were among 47 activists arrested in 2021 under the sweeping national security law imposed following massive anti-government protests four years ago. They were charged in connection to an informal 2020 primary election to pick candidates who could win the territory’s Legislative Council.

Prosecutors accuse the activists of trying to paralyze Hong Kong’s government and topple the city’s leader by securing a majority to veto budgets.

In court, Wednesday, Prosecutor Jonathan Man argued that unlawful means to subvert state power didn’t necessarily imply the use of force or physical violence.

“(In) the 21st century, social media, communications to the public is much easier and convenient,” he said, adding that it was easy to “manipulate” those channels for some “to endanger national security.”

The trial is widely considered as part of Beijing’s crackdown on the city’s once-vibrant pro-democracy movement. After the introduction of the law — which critics say is eroding the autonomy promised when Hong Kong returned to China in 1997 — many pro-democracy politicians and activists were jailed, went into self-exile, or disappeared from the city’s political scene.

A large number of young professionals and middle-class families also emigrated due to the erosion of Western-style civil liberties with the Chinese government’s crackdown on the territory.

The subversion trial involves many of the city’s most prominent activists, including legal scholar Benny Tai, former student leader Joshua Wong and former opposition party leaders Wu Chi-wai and Alvin Yeung.

Most of the 47 activists have been detained without bail for more than two years. Others were granted bail based on strict conditions. Thirty-one, including Tai, Wong, Wu and Yeung, entered guilty pleas in court, while 16 others pled not guilty in February.

The national security law criminalizes secession, subversion, and collusion with foreign forces to intervene in the city’s affairs as well as terrorism. Apart from the activists, pro-democracy publisher Jimmy Lai is also facing collusion charges under the law.