The leader of Hong Kong’s largest opposition party is not in the legal clear yet, as prosecutors are seeking to overturn his acquittal of an unlawful assembly offence stemming from an anti-government protest three years ago.

The Department of Justice applied on Monday for permission to appeal against last week’s District Court ruling in favour of Democratic Party chairman Lo Kin-hei, who was cleared of taking part in an unlawful assembly near Polytechnic University in Hung Hom on November 18, 2019.

Police received the High Court’s permission on Wednesday to rearrest the 38-year-old politician, who agreed to obey a travel ban as part of his new bail terms. A Democratic Party statement said it would continue to provide necessary support to its leader and his family.

Lo was among 10 people arrested during the illegal gathering at Science Museum Square, some 300 metres (984 feet) away from the university under siege by police. He was the only defendant acquitted in the case.

Four co-defendants were jailed for between 14 and 18 months after pleading guilty to taking part in an unlawful assembly, with a fifth defendant sentenced to up to nine months’ detention at a rehabilitation centre for the same offence.

Of the four remaining defendants who denied the charge, three were convicted of taking part in an unlawful assembly, with the other found guilty of possessing offensive weapons in a public place. They will be sentenced later this month.

In acquitting Lo, Judge Ernest Michael Lin Kam-hung noted the politician did not do anything to identify himself with the protesters at the scene, leaving room for reasonable doubt.

But Lin said the Democratic Party leader had drawn suspicion by allowing himself to be in the middle of conflicts between protesters and police that morning.

The judge dismissed Lo’s claims he was performing his official duties as then chairman of the council of the Southern district, which lies on the other side of Hong Kong Island, and found his presence at the scene was no coincidence.

On Wednesday, Court of Appeal justice Maggie Poon Man-kay released Lo on HK$5,000 (US$643) bail, on condition he surrender all travel documents, remain in Hong Kong, report to police weekly and notify them if he changes his address.

Taking part in an unlawful assembly is punishable by up to five years’ imprisonment.