There was a swift response from Beijing when the High Court ruled on Monday that the Hong Kong government’s anti-mask law was unconstitutional. Central government officials criticised the court for failing to support the government in its efforts to end more than five months of increasingly violent social unrest. For the first time, they suggested that the city’s courts do not have the power to declare a local law invalid by checking it against the Basic Law, the city’s mini-constitution. China’s top legislative affairs body argued that only the national legislature had the right to decide on issues of constitutionality. Beijing’s reaction left its critics in Hong Kong fearing for the erosion of the city’s independent judiciary. They also feared that Beijing would decide to hand down its own interpretation of the Basic Law and overturn the court ruling. But members of the pro-establishment camp dismissed those concerns, saying Beijing was only reiterating its position. What are the key issues in the controversy over the court ruling? Why is the court’s decision controversial? On October 4, after nearly four months of anti-government protests that were becoming increasingly violent, the Hong Kong government introduced a law banning the use of masks in public. It invoked the colonial-era Emergency Regulations Ordinance, a bill which gave the chief executive far-reaching power to enact certain laws in the face of “public danger” and “emergency”. Protesters ignored the ban, but 25 pro-democracy lawmakers turned to the courts, upset that the government had implemented the law without consulting the legislature. On Monday, the High Court ruled that the law, when invoked on the grounds of public danger, was unconstitutional, and that the anti-mask law was excessive. Beijing’s view on mask law ruling ‘could spell end of one country, two systems’ In Beijing, Yang Guan, spokesman of the State Council’s Hong Kong and Macau Affairs Office, said the court decision had a “serious and negative sociopolitical impact”. Zang Tiewei, spokesman for the Legislative Affairs Commission of the National People’s Congress Standing Committee (NPCSC), Beijing’s highest legislative body, suggested that only the NPCSC had the power to declare a local law unconstitutional. He was quoted in a strongly-worded article, published on China news agency Xinhua’s website, prompting fears that the next step might be for Beijing to give its own interpretation on the present case. Pro-democracy lawmaker Dennis Kwok Wing-hang shot back, calling it “the most shocking statement” and one that threatened to remove Hong Kong’s power to decide on judicial challenges. But pro-establishment lawmaker Priscilla Leung Mei-fun, a member of the Basic Law committee, said Zang might have been referring only to matters outside the scope of the city’s autonomy, as suggested in the Basic Law. What does ‘interpreting the Basic Law’ mean? Since the British handed Hong Kong back to China in 1997, the city has been governed by the “one country, two systems” principle, which promises a high degree of autonomy, including its judicial independence. The Hong Kong courts, with 163 common law judges and judicial officers, do have the power to interpret the Basic Law, but there are limits to the extent of what they can do. According to Article 158 of the Basic Law, the local courts can only interpret the mini-constitution in cases “within the limits of the autonomy of the region”. China slams Hong Kong court’s ruling of anti-mask law as unconstitutional In cases that involve “affairs which are the responsibility of the Central People’s Government, or … the relationship between the central authorities and the region”, the Hong Kong courts are required under the Basic Law to turn to the NPCSC for an interpretation. The Hong Kong courts are delegated their adjudicating power by the NPCSC. Once Beijing gives its interpretation, the Hong Kong courts are required to abide by it when they deliver their final ruling. When has Beijing ruled on Hong Kong matters? Since 1997, the NPCSC has issued a total of five interpretations. Two were sought by the city’s government, one by the courts and two were handed down by Beijing on its own accord. The first time Beijing gave its interpretation was in 1999. The issue was whether children born in Hong Kong to parents who were non-permanent residents would be entitled to the right of abode. The city’s Court of Final Appeal said yes, only to have that ruling overturned after the Hong Kong government sought an interpretation from Beijing. The NPCSC decided that only children with at least one parent who was a permanent resident should have the right of abode. Twice, Beijing acted on its own. Anti-mask law to quell Hong Kong protests ruled unconstitutional by High Court In 2004, the NPCSC issued an interpretation on its own, adding two new rules to Hong Kong’s electoral reform process, stating that the chief executive must first report any amendment to the method of election to a committee, which will decide if it is necessary. In 2016, two pro-independence lawmakers-elect, Yau Wai-ching and Baggio Sixtus Leung Chun-hang, were in court over their anti-China antics while taking their oaths. The case was still going on when the NPCSC controversially delivered its interpretation of the Basic Law with regards to the charges against them. The Hong Kong courts then disqualified them from taking office.