For the first time in the UK's modern legal history, two men could face an entirely secret criminal trial for terrorism charges, their identities, the proceedings, and the verdict concealed from the public record.

First reported Wednesday, the blackout sparked alarm among human rights campaigners, lawyers, and politicians.

“To hold trials entirely in secret is an outrageous assault on the fundamental principles of British justice," Clare Algar, executive director of UK human rights organization Reprieve, told the Telegraph.

Until Wednesday, the media was banned from reporting the trial at all. After a challenge to the gag order by UK media organizations, including the Guardian and the Daily Mail, the press won the right to cover a Wednesday hearing challenging the gag order. The court will rule on the appeal to the media blackout in the coming days.

The case involves two men, identified as "AB" and "CD," who will face terrorism charges in a criminal court. The Crown Prosecution Service successfully pushed for the secrecy, which would ban any public report on the trial's proceedings and outcome, on the grounds that it is necessary for the protection of national security, with the specifics unknown to the public.

Yet, lawyers challenging the secrecy warn that the blackout constitutes a severe threat to civil liberties and justice. In modern history, no UK criminal trial has been this closed to the public, although partial gag orders have been imposed.

"The Crown has sought and obtained an unprecedented order that the trial of two defendants charged with serious terrorism offenses should take place entirely in private with the identity of both defendants withheld and a permanent prohibition on reporting what takes place during the trial and their identities," said Anthony Hudson, who is providing counsel to media organizations appealing the gag order, at Wednesday's hearing, according to the BBC.

"This appeal raises important issues relating to not only the constitutional principle of open justice but the equally important principle of fairness and natural justice," he added.

"Transparency isn't an optional luxury in the justice system – it's key to ensuring fairness and protecting the rule of law," Shami Chakrabati, director of UK-based civil liberties organization Liberty, told the Guardian. "This case is a worrying high water mark for secrecy in our courts – extensive restrictions set without robust reasons or a time limit.

“For an entire trial to be heard in camera, this is unprecedented, very serious and worrying,” Keith Vaz, chairman of the Commons home affairs committee, declared Wednesday following the hearing, according to the Telegraph.

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