District Judge Stanley Chan Kwong-chi said it was clear the defendants’ actions had been “deliberate and premeditated”, at a time when Hong Kong’s public order situation remained volatile in the aftermath of the unprecedented social turmoil of 2019.

Chan said the court could not underestimate the event’s potential risk factor, as emotions could have run high, and the unruly might have taken advantage of that to incite violence.

“[The four defendants] openly defied the law,” Chan said. “The only mitigating factor is their guilty plea.”

Outside court, Chow Hang-tung, vice-chairwoman of the Hong Kong Alliance in Support of Patriotic Democratic Movements of China, which organises the annual vigil, said they were very disappointed with the ruling.

“It failed to respect our right to freedom of assembly, and it failed to draw any distinction at all between peaceful assembly and violent assembly,” Chow said. “The court seems to feel that any expression of political dissent is something that should be suppressed and subjected to deterrent sentences. I think this is wrong.”

Chow added that they were still planning to hold a vigil this year and had applied for a letter of no objection from the police. They have not yet heard back.

Prosecutors said police had to implement road closures and divert traffic along three streets in Causeway Bay for about two hours that night, while those in the park – most of them dressed in black – chanted political slogans and sang “political songs”.

Defence counsel Graham Harris SC had urged the court not to jail the four defendants, noting that they had worn face masks and played a passive role throughout the assembly, which he described as peaceful and orderly.

But the judge said all four defendants were political figures who knew full well they were taking part in an unauthorised public meeting involving a large crowd that would certainly generate traffic obstruction and public health risks amid the coronavirus pandemic.

“The fact that the participants were wearing masks or maintaining any kind of social distancing does not exonerate their culpability,” Chan said. “Literally speaking, the defendants were saying to the public at large they could enjoy more freedom than others.”

The judge said the defendants made “a wise decision” to plead guilty, in light of the strength of evidence against them in this straightforward case.

But he also noted that none of them had shown remorse because of their political convictions, which meant they were not suited for community service – not even Yuen and Leung, who had no prior convictions.

Chan further observed that Wong was a repeat offender – with six previous convictions, three of them similar to the present case, since August 2016 – and that the current offence was committed while he was out on court bail over another case.

He concluded a deterrent sentence was necessary and jailed all four defendants, granting a one-third discount to credit their timely pleas.

Before passing sentence, the judge noted that people had noisily chanted slogans as he left the courtroom after the last hearing, and reminded those present they were not in a public concourse.

“We have rules here, we have convention, we have etiquette,” Chan said. “No one can enjoy more freedom than others in this court of law.”

Still, a woman interrupted his delivery of the sentences by shouting “objection” twice in the packed courtroom.

The judge immediately warned that her conduct could be considered contempt of court and said people should air their grievances outside the courtroom.

“Lady, you don’t have a right of audience in this court,” he said. “Do not destroy, and make a mockery of, the rule of law in Hong Kong.”

Wong, 24, is currently behind bars for his roles in two anti-government protests in 2019, sparked by a now-withdrawn extradition bill. He was originally slated for release in November, before he was handed the latest jail term, which will run afterwards.

Their 20 co-defendants in the vigil case, including media tycoon Jimmy Lai Chee-ying, have not yet entered pleas.

Two other defendants, Nathan Law Kwun-chung and activist Sunny Cheung Kwan-yang, have fled the city and are wanted by police.

Law, a former opposition lawmaker, said he was devastated by the news of his friends being sent to jail for peacefully exercising their rights to protest and assembly.

“I could have been there, sitting behind bars, if I had not left Hong Kong,” Law said.

“The sentencing itself expresses a message that even the court is convinced that Hong Kong people do not have the natural rights to continue the [Tiananmen vigil], and deterring sentencing is needed to punish the activists who lit a candle that night.”

Samuel Chu, managing director of the Washington-based Hong Kong Democracy Council, said Beijing and Hong Kong authorities were trying to erase history by jailing those who dared to remember the 1989 Tiananmen protesters.

“The latest sentences also made clear the government’s intent: to keep the most recognisable and powerful voices for Hong Kong, like Joshua Wong, behind bars indefinitely by whatever means,” Chu said.