The prosecution offered no evidence in the case against two senior republicans, Sean Hughes and Padraic Wilson.
No reason was given by the prosecution barrister in court, but it is understood a number of key prosecution witnesses have withdrawn their evidence.
The judge duly acquitted both men.
Mr Hughes and Mr Wilson were facing charges including IRA membership and addressing meetings to encourage support for the IRA.
The charges dated back to 2005.
A major IRA membership trial has collapsed at Belfast Crown Court.