Lau, one of the six lawmakers disqualified in the 2016 swearing-in saga, was barred from contesting the by-election in the Kowloon West constituency, where she initially won her seat, after her nomination was thrown out.

Returning officer Franco Kwok Wai-fun ruled that Lau had not genuinely stopped advocating for self-determination for Hong Kong – which some officials have conflated with an unconstitutional pro-independence stance – despite her claim that she had ditched that position ahead of the polls.

The High Court lifted Lau’s election ban in May after finding the election official did not give her a proper opportunity to respond to the allegations against her.

On Friday, counsel for Chan and Kwok argued that the irregularity of Kwok’s conduct was not material, because Lau would have been disqualified regardless of whether she was given an opportunity to explain her political stance.

Hong Kong elections: mass disqualification of opposition hopefuls sparks political storm

Johnny Mok Shu-luen SC, for Kwok, emphasised that China’s top legislature had issued an interpretation of Article 104 of the Basic Law, the city’s mini-constitution, to the effect that people who did not genuinely uphold the Basic Law and pledge allegiance to the Special Administrative Region could not run for elections.

“The exclusion of a person who should not have been included in an election in the first place would not make an irregularity [in the nomination process] material,” Mok said. “[The election] should have gone ahead without this person in any event.”

Chan’s lawyer, Mike Lui Sai-kit, said Lau bore the burden to prove that her nomination should have been deemed valid, and that the returning officer’s decision had not caused any real or substantial prejudice to her.

But those arguments were rejected by Ribeiro, who said the crux of the problem was whether Lau’s nomination was fairly invalidated, especially when it might be possible Lau had indeed changed her stance.

“It may be the case that the candidate would be shown to have really failed the substantive requirements [to stand for elections], but that’s a subsequent question,” the judge added, referring to the requirements cited by Mok.

The top court, also presided over by justices Joseph Fok and Andrew Cheung Kui-nung, threw out the application for appeal without hearing from Lau’s lawyers. A written ruling will be delivered in due course.

Ex-lawmaker Au Nok-hin to plead guilty to illegal assembly charges, faces 5 years’ jail

With Chan’s disqualification, there are now five Legco vacancies in total. But the pro-government camp will continue to hold the majority, with 41 seats to the opposition’s 24.

Ousted lawmaker “Long Hair” Leung Kwok-hung has since 2017 challenged his removal for improper oath-taking, but lost at the High Court and Court of Appeal. Leung said his lawyers were still trying to take the matter to the top court.

In December last year, opposition lawmakers Au Nok-hin and Gary Fan Kwok-wai also vacated their seats after the top court ruled they were unduly elected in a 2018 by-election, as electoral officers had disqualified activists Agnes Chow Ting and Ventus Lau Wing-hong.

The most recent vacancy was created by pro-government lawmaker Jonathan Ho Kai-ming, who resigned to take up his current position as undersecretary for labour and welfare.

Speaking outside the Legco complex on Friday afternoon, Chan said she was “a little bit disappointed” by the ruling.

“I am in a passive position. This result was not caused by anything wrong that I’ve done or said; it was only about a procedural issue that took place before the by-election,” she said.

But Chan said it was not the appropriate time to organise a by-election, even though critics have suggested that polls could be safely held despite the ongoing pandemic, with face-to-face classes starting to resume next week.

“Classes can be resumed, but only for half-day and after a lot of preparatory work. Many extra-curricular activities were also banned ... so we cannot put an equals sign between class resumption and elections,” Chan said.

But Lau on Friday said the government must organise a by-election to fill as many vacancies as possible.

“I welcome the top court’s reasonable decision today. But this decision would not help protect Hong Kong people’s election rights,” she said, pointing to election officers’ broad power to disqualify candidates as the reason “why Hong Kong’s human rights have backtracked a lot”.

A spokeswoman for the Constitutional and Mainland Affairs Bureau, however, said the government was unlikely to stage any by-election in the coming year.

“Many voters are now living, working or studying in the mainland, and could not return to the city to vote because of quarantine requirements. Elderly voters will also avoid going to polling stations because of the risk of infection,” the spokeswoman said. “So to ensure that the election will be fair and open, and to avoid spreading the virus, we have no plan to organise a by-election before the Legco polls slated for September next year.”

In a joint statement, pro-establishment legislators said it was regrettable that Chan was leaving the Legco, and thanked her “for her efforts and contributions in the past two years”.

Commenting on the case, Democratic Party legislator Helena Wong Pik-wan said the result showed that the power of election officials to disqualify candidates created unfairness for both camps.

Wong said rather than organising by-elections, the government should hold general polls for Legco as soon as possible. City leader Carrie Lam Cheng Yuet-ngor previously cited the Covid-19 pandemic in postponing the Legco elections, originally slated for September 6, by one year.

Pro-Beijing lawmaker Vincent Cheng Wing-shun, of the Democratic Alliance for the Betterment and Progress of Hong Kong, also said it was unfair for Chan to be unseated.

“Chan did not do anything wrong; it was the government’s procedural mistakes that caused her to lose her seat,” he said, adding the disqualification “was not fair to her supporters and her”.

Cheng, however, disagreed with the pan-democrats’ argument that a new vote should be held, maintaining that “a fourth wave of infections could be coming”.