City leader Carrie Lam Cheng Yuet-ngor had invoked a colonial-era emergency law, on the grounds of public danger, to prohibit facial coverings at demonstrations in a bid to quell months of anti-government protests, sparked by a now-withdrawn extradition bill.

The Court of Final Appeal has upheld the legality of the ban for all public assemblies, meetings and processions, saying it was a proportionate measure necessary for dealing with the frequent violence that accompanied the protests.

Prosecutors alleged that Wong and Koo took part in the October protest knowing it was not sanctioned by the police commissioner.

Most of the participants were said to have worn masks and chanted slogans including the rallying cry “Five demands, not one less”. The pair’s involvement could be seen in multiple news clippings. In particular, Wong could be seen accepting media interviews and taking a selfie with a foreign journalist during the procession, while Koo held a long, narrow flag emblazoned with the words “Glory to Hong Kong”.

In January, Wong pleaded guilty to knowingly taking part in an unauthorised assembly and using a facial covering at an unauthorised assembly. Koo was convicted on Tuesday of knowingly taking part in an unauthorised assembly after a trial last month.

In Tuesday’s mitigation hearing, Wong’s lawyer, Jeffrey Tam Chun-kit, urged the court to pass a lenient sentence, such as a fine or suspended jail time, in view of the peaceful nature of the march.

“He did not wear the mask to conceal his identity; he was only there to protest,” Tam said. “He was not there to commit violence or evade criminal liability.”

But Magistrate Daniel Tang Siu-hung said taking part in an illegal, large-scale protest, notwithstanding the absence of violence or vandalism, in general warranted a deterrent sentence – a principle laid down by the Court of Appeal in recent protest-related proceedings.

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Koo, speaking for himself at the bar table, said he was set to undertake surgery for rectal cancer, but would “cooperate with” the court’s ruling as he was prepared to serve time in prison for the 11th time in his life. Instead of requesting a lighter sentence, Koo asked the magistrate not to show leniency as he would continue to break the law in the future.

“Next time, I will deliberately break the national security law. Do not be lenient or take pity on me,” Koo said before making a political speech.

Passing sentence, Tang set a starting point of six months in jail for the unauthorised assembly offence to reflect the defendants’ leading roles in the march. He trimmed two months from Wong’s term in view of his guilty plea, and one month from Koo’s, as he did not dispute most parts of the prosecution’s case in the trial and therefore saved the court’s time.

The magistrate also jailed Wong for 10 days for violating the mask ban, but ordered the sentence be served concurrently with the other charge.

Wong is already serving a 13½-month prison term for incitement and organising an unauthorised assembly over a 15-hour siege of police headquarters in Wan Chai on June 21, 2019.

But Wong is set to plead guilty to still more charges at the end of this month in a separate case connected to his role in an unauthorised assembly on June 4 last year, when residents defied a government ban on gathering in public and flocked to Victoria Park to commemorate the 1989 Tiananmen crackdown.

Held every year since 1990, the annual vigil was banned for the first time ever by police, who cited pandemic-related social-distancing concerns.