Two men who pleaded guilty to membership of the IRA's youth wing more than 30 years ago have had their convictions set aside.
They were denied access to a lawyer and were both 16 when they were convicted. Both men are now in their late 40s.
John Fitzpatrick, originally from Belfast, and Terence Shiels, originally from Creggan in Londonderry, admitted membership of Fianna na hEireann.
The cases were referred to the court by the Criminal Cases Review Commission.
Mr Fitzpatrick was also convicted of involvement in a gun attack on an army patrol in 1976 when Mr Shiels allegedly admitted possession of a handgun.
The landmark decision in the Court of Appeal centred on the fact that neither had access to a lawyer or had a parent present when they were questioned by police over 30 years ago.
This was against the judge's rules which were in operation at the time and it's because of this breach that the Court of Appeal held that the convictions were unsafe.
It is thought that this decision could lead to challenges in similar convictions and the Criminal Cases Review Commission is understood to be preparing to refer a number of files to the Court of Appeal.