Chow Hang-tung, 41, is standing trial for "incitement to subversion" along with her former colleague Lee Cheuk-yan, 69. They face years behind bars if convicted.

The pair were leaders of the now-defunct Hong Kong Alliance, a group that formerly organised candlelight vigils to mark China's deadly 1989 crackdown on demonstrators in Beijing's Tiananmen Square.

China imposed a national security law on the financial hub in 2020 following huge and sometimes violent pro-democracy protests the previous year. The Alliance's leaders were charged in 2021 and have been behind bars since.

Chow, a Cambridge-educated barrister who is representing herself, smiled widely at supporters in the gallery as she entered the courtroom.

"Rather than a challenge to the defendants, this prosecution is, in fact, a trial of the law itself," she said in her closing submission.

"Sooner or later the law will have to confront the fundamental contradiction between dictatorship and the rule of law," she said, adding that she hoped the court "will make the right choice".

She told the three-judge panel earlier it was a "weird" criminal case because the defendants did not dispute the facts.

"The defendants fully embraced the actions that the prosecution alleged to be crimes," Chow said.

"What is really at dispute is what the law suppresses and what it protects," she said.

- 'End one-party rule' -

Prosecutors accused Chow and Lee in their closing arguments on Monday of "endangering national security in the name of human rights", adding that freedom of speech and association are "not absolute rights".

They said the Alliance had repeatedly called to "end one-party rule" in China, which they said amounted to overthrowing or undermining the political system established by the Chinese constitution.

Chow said the group's stance of "end one-party rule" means "to put an end to a state of unrestrained power".

She told the court the Chinese constitution "exists to restrain those in power, not to restrain ordinary people".

She said the prosecution's allegations that the group incited people to contravene the constitution were "completely absurd".

Lee's lawyer said on Monday the court must not pay "lip service" to human rights, and that the right to criticise state organs was constitutionally protected.

- 'Vague, arbitrary' -

Lee and Chow face a maximum penalty of 10 years' imprisonment.

The two defendants grinned at supporters and made peace signs as Tuesday's hearing ended.

Judge Alex Lee said as the court adjourned that the panel hoped to deliver a verdict in July.

A third defendant, 74-year-old former lawmaker Albert Ho, pleaded guilty in January.

Rights groups have slammed the trial.

Amnesty International's deputy regional director Sarah Brooks said in a statement on Monday that "the prosecution's case relies on vague, overly broad and arbitrary definitions of 'subversion'," and called for the charges to be dropped.

Urania Chiu, a law lecturer researching Hong Kong at Oxford Brookes University, told AFP the verdict could have wider consequences.

"If the prosecution's broad and circular understanding of the offence is accepted (by the court), legitimate critiques of Chinese government policies... however minor, will easily be criminalised", she said.