As health experts in Hong Kong call for masks to be made mandatory to tackle coronavirus, a ban on their use that was introduced in response to protests has been largely upheld by the appeal court. The court also used its ruling to push back at accusations that its role in assessing the constitutionality of laws was an affront to Beijing. The judgment, delivered on Thursday afternoon, said Hong Kong’s chief executive could use colonial-era laws to make emergency decrees for public safety and that banning masks was constitutional at unlawful gatherings. But it also found that banning masks at lawful gatherings and allowing police to demand their removal was unconstitutional. Hong Kong’s mask ban was introduced in October as widespread protests in the city grew increasingly violent. The chief executive, Carrie Lam, invoked the colonial-era emergency regulations ordinance (ERO), categorising the protests as a state of “public danger”, to ban the wearing of masks at both lawful and unlawful assemblies. “The violence and damage are mostly caused by protesters wearing masks and dressed in black outfits,” said Thursday’s court judgment. “At the same time, it is a common phenomenon that many other protesters participating in public assemblies and processions who are not involved in violence are also wearing masks and dressed in black outfits.” The judgment said there was “nothing objectionable” in Lam having the power to determine whether a public danger existed, and the chief executive was “evidently the only suitable person to make the call”. “That said, it does not follow that the CE could act freely without any rein as she wishes,” it added. The court found the mask ban, which indisputably “imposed restrictions on fundamental rights”, did not meet standards of proportionality in applying to lawful gatherings, and noted the risk to bystanders or people who joined a lawful rally and did not realise when authorisation had been revoked. “[A] total ban of facial coverings from all public demonstrations, processions and gatherings cannot pass the test of reasonable necessity even in the context of the public danger in which the [anti-mask law] is meant to address,” the judgment said. It added that police already had powers to seek identification of suspects, and found the powers granted to police to physically remove masks was unconstitutional. Speaking outside court, one activist, Leung Kwok-hung, popularly known as “Long Hair”, said he was disappointed with the ruling, the South China Morning Post reported. “The definition of ‘public danger’ is too wide, it will allow the chief executive to abuse his or her power in order to avoid ordinary people from exercising their basic rights such as freedom of assembly or freedom of speech,” he said. The mask ban in October prompted further protests as well as legal challenges by pro-democracy legislators, and in November the high court ruled the ban and the use of the ERO was unconstitutional, a decision that angered Beijing. Under the “one country, two systems” framework, the city is meant to enjoy semi-autonomy from China until 2047. “Whether Hong Kong’s laws are consistent with the Basic Law can only be judged and decided by the [National People’s Congress standing committee],” said Zang Tiewei, the spokesman for the committee, which is China’s top legislative body. “No other authority has the right to make judgments and decisions.” However, in Thursday’s ruling the court appeared to defend itself against this charge. It said laws could be adopted and later found to be in contravention of the Basic Law, Hong Kong’s mini-constitution, which does not “in any way diminish the authority of the NPCSC’s decision”. There were 632 people arrested under the law, but only three were arrested solely in relation to that offence. Sixty-one were charged. The maximum penalty is one year in prison or a fine of HK$25,000 (£2,600). Since the coronavirus pandemic took hold the law has been criticised for contradicting public health measures. Hong Kong, like many other Asian cities, embraces the use of masks to prevent the spread of disease. This week health experts called for the wearing of masks to become mandatory in Hong Kong. Ho Pak-leung, a microbiologist at Hong Kong University, told local radio masks were effective to an extent, and that some infection clusters may have been related to people not wearing masks. Ahead of the ruling legal academics called for the Hong Kong government to repeal the law regardless of the outcome, to avoid confusion that could put people’s health at risk.