The Nauru Court of Appeal has accepted an appeal on a permanent stay granted to a group charged over anti-government protests four years ago.
The court overturned the permanent stay on charges that the group, dubbed the Nauru 19, had been facing since the protest.
The group includes former MPs and their supporters.
One member, former president Sprent Dabwido, died in Australia last month.
He had cancer.
The permanent stay ruling was made by Australian judge, Geoff Muecke, who was specially brought in by the Nauru government to hear the case.
Mr Muecke had found the Nauru 19 trial could not be fair, that the government had thwarted legal representation and it was persecuting the defendants.
But the Court of Appeal has set aside the order made by Mr Muecke, and the Chief Justice is to decide what happens next.
In addition to the permanent stay Mr Muecke had an earlier ruling overturned.
He had declared the Criminal Procedure Amendment Act 2018 to be inconsistent with the Nauru Constitution and that it was wholly void.
Mr Muecke also ordered the Republic of Nauru to re-imburse the defendants $US154,864 dollars, saying that a failure to pay might lead to the case being stayed.
He had also ordered the defendants be paid costs of $US56,238
Each of these has been set aside.