The high-profile arrest of 53 members of the opposition on suspicion of breaking the national security law could prove to be a defining moment for Hong Kong. The cases will put the city’s legal system and the implementation of the security law to the test.

The stakes are high. The arrests involved raids across the city by almost 1,000 police officers, and among those held were 16 former lawmakers. Investigations are continuing. Meanwhile, four media organisations have been required to provide information to assist police inquiries.

This sweeping operation has, once again, shone the international spotlight on Hong Kong and sparked fresh questions about where the red lines lie under the security law passed by Beijing last year. The allegations are serious and the offences can lead to sentences of up to life imprisonment.

Those arrested were involved in last year’s primary run-off vote to select opposition candidates for the Legislative Council election, which was later postponed. Officials allege the primary was part of a subversive strategy intended to paralyse and ultimately overthrow the government, bringing chaos to Hong Kong.

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Mass arrests of Hong Kong opposition lawmakers, activists under national security law

Mass arrests of Hong Kong opposition lawmakers, activists under national security law

Among those arrested was Benny Tai Yiu-ting, one of the organisers of the 2014 Occupy protests, who is said to have outlined the strategy in a newspaper article. It was written before the passing of the security law while the primary took place after the law was enacted.

The primary drew votes from 610,000 people, but police say those who merely voted will not be prosecuted.

These are controversial arrests. The police say primaries are not in themselves unlawful and it was the strategy to paralyse Hong Kong that was being targeted. Legal experts have raised questions about whether there is sufficient evidence or legal grounds to secure subversion convictions under the security law.

Benny Tai among opposition figures released by police after crackdown

Executive Council member Ronny Tong Ka-wah, and Basic Law expert Maria Tam Wai-chu were among those suggesting more cogent evidence might be needed.

Grenville Cross, former director of public prosecutions, pointed out that a higher evidential threshold needs to be met if those arrested are to be charged and taken to court.

The Department of Justice must ensure sufficient evidence exists before charges are laid and cases taken to court. Convictions require proof beyond reasonable doubt.