Hong Kong’s West Kowloon Magistrates’ Court granted bail Thursday to 15 of the 47 opposition figures charged with subversion under the region’s controversial national security law after organizing and participating in an unofficial primary election last July. A challenge from the prosecutors, however, meant that all 15 were kept in custody. In a “surprise u-turn,” four of the defendants were released on Friday after prosecutors revoked their challenge to the court’s bail decision.

The defendants were among the 53 opposition figures arrested in dawn raids on January 6. The raids, which have been the subject of censure from international rights groups, were the largest crackdown on opposition since the national security law was promulgated in July last year. Amnesty International’s Asia-Pacific Regional Director Yamini Mishra said of the raids:

This shocking crackdown on Hong Kong’s political opposition – sweeping up candidates, activists and pollsters alike – is the starkest demonstration yet of how the national security law has been weaponized to punish anyone who dares to challenge the establishment. This ruthless legislation gives the Beijing and Hong Kong authorities free rein to crush any dissenting views and puts all government critics at risk of imprisonment.

Police announced on February 28 that charges of “conspiracy to commit subversion” had been laid against 47 of those arrested. After a four-day bail hearing, at the outcome of which bail was granted to only 15, prosecutors immediately lodged an appeal, forcing all 47 defendants to be remanded in custody.

Prosecutors dropped their bail challenge in respect of four defendants on Friday. Under the terms of their bail, the four must refrain from saying or doing anything which could be deemed as endangering national security through social media platforms or any publications, participating in any forms of elections, or getting in touch with foreign officials or legislators.

The other 11 granted bail will be brought before Justice Esther Toh Lye-ping of the Court of First Instance for a hearing of the prosecutors’ appeal on Thursday and Saturday.