Britain transferred sovereignty over Hong Kong to China on July 1, 1997, when Hong Kong became a Special Administrative Region of China (HKSAR). It was to be governed by a Basic Law, a mini-constitution, in accordance with Deng Xiaoping's formula of "One Country, Two Systems." Hong Kong was to enjoy a high degree of autonomy.
Freedom from mainland control is stipulated in Chapter I: General Principles. Article 5 states that "The socialist system and policies [of The People's Republic of China] shall not be practiced in the Hong Kong Special Administrative Region, and the previous capitalist system and way of life shall remained unchanged for 50 years."
In the past few years, China's Central Government has increasingly encroached on Hong Kong's liberties. These violations were forecast in our book published twenty years ago in 1996.