The demonstration was part of the months-long anti-government movement, sparked in June last year by opposition to the now-withdrawn extradition bill.

In June, Eastern Court Magistrate Lam Tsz-kan allowed Hui to press ahead with three charges, including one of shooting with intent, an offence punishable by life in prison. The officer was originally scheduled to enter his plea on August 31. Kwan applied to the High Court for a judicial review in a bid to quash the private prosecution last week.

What does the law say about private prosecutions and the justice’s minister’s power over them?

Section 14 of the Magistrates Ordinance allows residents to launch criminal complaints, although the secretary for justice can intervene to take over or abort the case. The right derives from the common law system the city inherited from the previous British colonial government.

According to former director of public prosecutions Grenville Cross, private prosecution provides a course of action for an individual seeking to see the law enforced. Every person has the same right as the Department of Justice (DOJ) to institute proceedings.

But the right is not absolute, Cross noted. Article 63 of the Basic Law, the city’s mini-constitution, vests the DOJ with ultimate control over criminal prosecutions “free from any interference”.

“The secretary for justice, therefore, has wide powers of intervention, in appropriate cases,” he said.

Justice secretary says ‘improper’ intent, political motivations reasons to quash private criminal prosecutions

How often has the justice secretary intervened in private prosecutions?

In a judgment that set out the boundary for the right in 2016, Court of First Instance Mr Justice Patrick Li Hon-leung cited figures provided by the DOJ.

Between 1996 and 2013, magistrates approved 51 applications for private prosecutions. Two were taken over by the department, in what Li described as “extremely rare” cases.

In deciding whether to take over a case, prosecutors will look at the public interest, wishes of the parties, if the action has a reasonable chance of success and whether the trial will be fair, among other issues, according to the Prosecution Code.

Cross was involved in terminating a private prosecution case concerning a man convicted of false accounting in the District Court in 1998. The man sought to bring charges against 10 people involved in his trial, including the prosecutor, two officers with the anti-graft watchdog and seven witnesses.

The DOJ decided the effort was misconceived after reviewing the case with police, and an independent assessment by senior barristers. Cross said he explained his decision to the Legislative Council in November 1998. Ted Hui is demanding Cheng or the DOJ do the same.

The DOJ previously intervened in a case linked to a judgment handed down by the Court of First Instance. Businessman Koon Wing-yee and several others were tried in 2012 on charges of blackmailing Hui Chi-ming, the chairman of energy holding company Sino Union, three years earlier, but all were acquitted. In 2012 and 2016, Koon and one of his co-defendants initiated private prosecution against Hui and a senior Sino Union employee respectively, accusing them of blackmail. The DOJ ended both bids. The co-defendant filed a judicial review and lost, while Koon has filed a separate judicial review over the decision.

What other private prosecutions are opposition legislators pursuing?

The case involving the police officer is the second time Hui has received the go-ahead this year to lodge a private prosecution over incidents relating to the anti-government protests.

Hui was given permission in June to privately lay a charge of dangerous driving against 59-year-old taxi driver Henry Cheng Kwok-chuen. He accused the driver of ramming a cab into a crowd of protesters in Sham Shui Po in October last year. The case is scheduled to be heard on August 31.

Hui’s colleague Raymond Chan Chi-chuen, the chairman of the People Power party, won approval to lay a count of common assault against pro-Beijing rival Kwok Wai-keung, who allegedly attacked him during a chaotic House Committee meeting in the Legislative Council on May 8.

Principal Magistrate Peter Law Tak-chuen agreed to adjourn the case to September 14 to give Kwok time to weigh his legal options and for the DOJ to consider taking over.

Hui said on Wednesday that with Cheng’s move, it was possible his case against the taxi driver and Kwok could also be discontinued.

Are these moves linked to the national security law? What about the timing of the decision to intervene?

Cross said he believed the justice minister’s move was unrelated to the new law. But Hui said that even though the move was not directly related to the national security law, it was a reflection of the current political climate. He hoped his bid would help ease “the tense social atmosphere”.

“It was unwise for the government to close down the path when people are already questioning whether the rule of law is dead,” he said.

Barrister Anson Wong Yu-yat said it was difficult to comment on the justice secretary’s move without knowing her reasoning. But Wong said Hui could still file a judicial review to challenge the action.

Additional reporting by Tony Cheung