Hong Kong, a British colony until 1997, when China resumed sovereignty, is governed by a mini-constitution, the Basic Law.
The city maintains an independent judiciary, and residents enjoy greater civil liberties than residents of mainland China. Hong Kong has a robust tradition of free speech.
Democratic groups say Beijing has chipped away at those freedoms, citing a proposed election law that would limit voting reforms.
China had promised free elections for Hong Kong's chief executive in 2017. But the government rejected a call for open nominations, instead proposing that candidates would continue to be chosen by a committee dominated by Beijing.
The current city leader, Leung Chun-ying, has clashed with the pro-democracy opposition. After the crackdown on protesters, some called for his resignation.