The High Court on Thursday refused to grant bail to pro-democracy media tycoon Jimmy Lai after hearing a fresh application by the national security suspect.
Lai is accused of colluding with foreign forces.
He had once again been remanded in custody last week after the Court of Final Appeal upheld a government challenge to a lower court's decision to release him into house arrest.
The Apple Daily founder then filed a fresh application for bail at the High Court.
But after hearing arguments from the defence and prosecution on Thursday, Justice Anthea Pang – a designated national security judge – decided to keep Lai behind bars.
"Having considered all relevant materials... I am not satisfied that there are sufficient grounds to believe that he will not continue to commit acts that endanger national security," she said.
Pang said she would publish the reasons for her decision at a later date.
The Court of Final Appeal said last week that the High Court judge who released Lai last December had misconstrued the bail provision in the national security law.
On Wednesday, Lai was also arrested by the police on suspicion of conspiring with others to collude with external elements to endanger national security, as well as on suspicion of assisting an offender.