Hong Kong’s new top judge took office Wednesday vowing to defend the rule of law in this former British colony, where activists worry that the territory’s semiautonomous status is eroding under Chinese rule.

While Beijing resumed sovereignty over Hong Kong in 1997, it let this thriving financial hub retain its British-influenced political, economic and legal systems and Western-style civil liberties. But 13 years on, some local activists fear that the territory’s insulation from Chinese authoritarian rule is weakening, pointing to Beijing’s willingness to issue rulings that trump the Hong Kong government and Hong Kong courts.