Pro-democracy activist Joshua Wong and district councillors Lester Shum, Tiffany Yuen and Jannelle Leung were jailed for between four and 10 months on Thursday for taking part in a June 4 vigil that had been banned by the authorities.
Wong received 10 months behind bars, Shum six months and the two women four months.
They had pleaded guilty to gathering at Victoria Park last year to commemorate the victims of the crackdown in Beijing in 1989.
For the first time ever, authorities refused to grant permission for the annual candlelight vigil, citing the pandemic. Nevertheless, thousands of people turned up.
District Court judge Stanley Chan said there had been a potential risk of violence breaking out at the event, even though it passed off peacefully, as always.
"With the 2019 unrest still lingering, the gathering of some 20,000 participants on a special night like June 4 meant emotions could run high, and unruly elements could take advantage of the situation and incite violence," he said.
Chan added that the crowd of people had led to the closure of nearby roads and said this could have generated a health hazard due to the pandemic.
"Literally speaking, the defendants were showing to the public they enjoyed greater freedoms than others," the judge said.
He dismissed the defence's argument that the defendants only played a passive role in the vigil, saying the four are political figures and had uploaded photos to social media showing they were taking part.
Chan ruled that the only mitigating factor was the defendants' guilty pleas, and said he had reduced their sentences by a third to reflect this. He said Wong was on court bail when he committed the offence and this was an aggravating factor.
The judge also said that there was a need to deter others from committing similar offences in future.
In April, Wong was jailed for four months after pleading guilty to joining hundreds of others in an unauthorised assembly on October 5, 2019.
His new prison sentence is to be served after the four-month term comes to an end.
Wong, Shum and Yuen are also accused of breaching the national security law by holding primary polls to select Legco candidates, and they were already behind bars awaiting trial.
Twenty-two other pro-democracy activists have also been charged over last year’s vigil, and are due in court next month. Two of them, Nathan Law and Sunny Cheung, have fled Hong Kong.