Other attorneys have raised their objections with judges. Starting in July, the barrister Douglas Kwok told me, he began routinely criticizing prosecutors in open court for bringing charges without concrete evidence. After one such episode, the room erupted into applause, fellow barrister Chris Ng said. (Even Chen’s counsel complained to the courts about the prosecution’s tactics, telling a judge in December that the justice department had disclosed “zero evidence,” concerning her case, despite three months of requests. She is free on bail.)

If judges seem to give prosecutors leeway, that’s by tradition. Scholars note that the British-derived common-law system used in Hong Kong allows prosecutors broad powers intended to be used with discretion. At the same time, Hong Kong still carries many laws that have not been revised, revoked, or reinterpreted since the territory’s colonial days. Hong Kong’s version of the 1714 Riot Act of Great Britain, for example, was passed to bar another Communist-backed uprising, which terrorized residents in the 1960s. The ordinance tightly restricts groups and their behavior. In the strictest interpretation, even legal protests staged during the past year might not pass muster. (One challenge of prosecuting people who joined what became a broader democracy movement is the absence of historical cases that might define what it means to engage in a riot, Simon Young, a law professor at the University of Hong Kong, told me. Is merely being present enough to convict? Must the defendant breach the peace? Does that person have to share the intention of everyone else who disturbed the peace and riotously assembled? With few precedents, judges have given prosecutors ample time and space to shape their claims.)

Prosecutorial discretion offers ripe chances for abuse in a system that already lacks full transparency or much constraint, Alvin Cheung, a Hong Kong barrister and doctoral candidate at NYU School of Law, told me. The system’s weaknesses have permitted officials to wield Hong Kong’s ordinances, backed by common-law rulings, in novel ways that can stymie the government’s dogged critics.

In 2016, a magistrate convicted three student activists, including Joshua Wong, of leading a crowd into a locked government courtyard two years prior, the incident that sparked an unsuccessful occupation for democratic rights. After two of the three students finished their sentences, a dissatisfied secretary of justice petitioned the Court of Appeal to impose prison terms. Cheung believes that the prosecution was “motivated by political animus,” citing news articles in which unnamed career prosecutors advised the justice secretary to forgo additional punishment. The city’s highest court released the young men after several weeks behind bars, ruling that the appellate bench had erred. (Similar dissent surfaced last year, too: In late July, several people claiming to be public prosecutors signed an open letter denouncing the current justice secretary for her support of the police and what they termed political calculations in cases against demonstrators.) While the protesters were held, Cheung noted, prosecutors routinely declined to press serious charges against pro-Beijing demonstrators accused of attacking their opponents. More recently, nine pro-democracy activists and lawmakers were tried in 2018 for organizing and leading the 2014 protest. All were convicted last April, and two, both university professors, were imprisoned.