 Complete the following phrase:  Demosistō advocated a referendum to determine Hong Kongs sovereignty with the goal of obtaining autonomy after 2047, when the one country, two systems principle as promised in the Sino-British Joint Declaration and the Hong Kong Basic Law is supposed to expire. It won a seat in the 2016 Legislative Council election with its 23-year-old chairman Nathan Law becoming the youngest candidate ever to be elected. In 2017, Law was disqualified from the Legislative Council over the 