A Hong Kong judge ruled Friday the police had “prematurely curtailed” their investigation of a Philippine domestic worker being exploited by her employer, a biting assessment of the city’s failure to protect victims of human trafficking.

The landmark ruling marks a rare victory for migrant worker activists, who have long argued that the city’s 340,000 domestic workers – mostly women from the Philippines and Indonesia – are acutely vulnerable to various forms of abuse and exploitation.

Last year, Brian Apthorp, a British permanent resident, was convicted of committing indecent assault against his domestic helper – referred to in legal documents as “CB.”