Gerry Conlon. who spent 15 years in prison for a crime he did not commit, has called for the immediate release of Marian Price.
He was speaking outside the courthouse in Derry on Wednesday where her case was due to be heard.
The 58-year-old is awaiting trial on charges linked to a dissident republican Easter rally in Derry.
She is currently being treated in hospital.
Mr Conlon, one of the Guildford Four, joined around 20 protestors outside the court.
"To think that a process of law is being usurped by politicians in order to hold a woman, without her lawyers being able to see the accusations against her, is an abuse of justice, it is a human rights' issue.
"If there is evidence to say someone has committed a crime it should be placed before the court, their lawyer should have access to it and the accusations should be made open and public.
"Justice has to be fair, open and transparent and that it is why I am here. It is not fair, it is not open and it is certainly not transparent."
Mr Conlon said holding people indefinitely based on secretly obtained evidence is a backward step for the justice system.
"These are the things the generals did in South America.
"They arrested people and they imprisoned people based on the words of someone , on secret evidence.
"This is what they did in totalitarian regimes in the Middle East, this is what they did in the Soviet bloc in the 1970s and 80s.
"If Marian Price has a charge to answer it should be done in an open court, the evidence should be made available to her lawyers, it should not be secretive, because where does it stop.
"This is supposed to be a society that is evolving, not regressing, this is internment by remand."
Ms Price is charged with addressing a meeting in support of a proscribed organisation in Derry at Easter last year.
She was arrested and returned into custody on the direction of the then Northern Ireland Secretary of State Owen Patterson.
She had been on licence.
Mr Patterson revoked the licence after she was photographed and filmed holding a piece of paper from which a masked man read a statement during a dissident republican Easter commemoration rally in Derry city cemetery.
She had been in Hydebank Prison but was eventually moved to hospital after her lawyers successfully campaigned to have her moved due to ill health.
In court on Wednesday District Judge Barney McElholm adjourned the case until next week after saying the court does have the power to convene in a hospital setting.
This is provided appropriate secure and suitable accommodation could be made available by the hospital authorities.
However, he said the hearing would not take place in a ward or at Ms Price's hospital bedside.
Mr McElholm said, before he made his final decision he wanted the hospital staff to be fully advised and briefed on the nature of a hospital court hearing, should it go ahead.
He also said because the hearing would be a preliminary enquiry Ms Price would not have to give evidence, nor could she be cross examined