Yang Jianli, president of Initiative for China, Teng Biao, a human-rights lawyer, and Hu Jia, winner of the Sakharov Prize, are former political prisoners of China. They write:

Thousands of pro-democracy demonstrators turned out in Hong Kong on Monday, defying a government crackdown over the weekend that saw riot police using tear gas, pepper spray and batons against protesters. As demonstrations grow against Beijing's violation of its promise to allow universal suffrage, there is a danger that the infamous 1989 massacre in Tiananmen Square could be repeated in Hong Kong.

The crisis began in June, when Beijing released a white paper that reneged on the "One Country Two Systems" principle laid out in the Sino-British Joint Declaration of 1984 and the Basic Law, Hong Kong's constitution. China had pledged that Hong Kong could rule itself on all matters apart from defense and foreign affairs, and voters could freely choose their own leader.

Instead, the white paper claimed that Beijing has complete jurisdiction over Hong Kong, with the only autonomy being what the central government decides to grant. All aspects of local government are subject to oversight by Beijing, and even judges must meet its standard of patriotism.