The group called the Nauru 19 believes it has grounds to still push for a permanent stay on charges over an anti-government protest four years ago.
Last week the newly set up Nauru Court of Appeal overturned a permanent stay granted last year by Supreme Court judge Geoff Muecke.
The stay had meant a long delayed trial process for the Nauru 19 ended.
But the Court of Appeal ruled Justice Muecke went beyond his commission and was not empowered to determine constitutional issues.
A spokesman for the accused, former Nauru justice minister Mathew Batsiua, said the ruling, in a sense, means they are 'back to square one,' but he says the reasons Justice Muecke detailed for granting a permanent stay remain.
"We also have to note that the Appeal Court did not dispute the misconduct of the Nauruan government, which was mentioned in the Justice Muecke judgement, about the government being overly interested in this case, having a running commentary on this case in parliament, the bullying, the intimidation, the blacklisting, the persecution - all that still exists," Mr Batsiua said.
He asked how someone could get a fair trial in Nauru under those circumstances.
The Nauru Government meanwhile has welcomed the decision, the first ruling by the new Court of Appeal.
The Nauru Justice Minister David Adeang said "the first sitting of the court was historic and highlighted the great strides Nauru has made in creating an accountable and high quality legal system."
Until last year the final court of appeal in the Nauru legal system was the Australian High Court but the government secretly ended this arrangement..
The Nauru 19 had previously successfully appealed to the Australian court.
In September last year Justice Muecke, who had been brought in by the government as an independent judge specifically to hear the Nauru 19 case, issued a 107 page judgement in which he was highly critical of Nauru officials, from David Adeang down.
"In denying the defendants legal representation and resisting their obtaining legal assistance, in imposing a "blacklist", in forbidding any plea bargaining, and in publicly denouncing and vilifying the defendants and those seeking to assist them, the Executive Government of Nauru has displayed persecutory conduct towards these defendants which is all the more serious in the unique context of Nauru," Justice Muecke said.