Stephen "Rossi" Walsh walked free from the Four Courts in Dublin yesterday after a High Court judge ruled that a temporary holding warrant under which he was being detained in Cloverhill Prison was bad.
However, lawyers for the Director of Public Prosecution said there would be a fresh attempt to seek his detention.
Walsh (55), Sandymount, Dublin, completed a 15-year sentence last February which was imposed on him by the Special Criminal Court in November 1993 for arson of Collins' pub, Ballybough, Dublin, in September 1992.
On completion of that sentence, he was due to serve an additional 12 months in prison on foot of assault charges brought against him while he was in custody.
Last week Walsh initiated proceedings challenging the lawfulness of his detention on those charges at Cloverhill Prison. He contended that the warrant on which he was being held was bad.
Lawyers for the DPP told the court last Thursday they were unable to find the sentence warrant at that point but believed it was located in Mountjoy Prison and sought more time to conduct a search.
Mr Justice Philip O'Sullivan agreed to grant more time and adjourned the matter until yesterday. When the Article 40 proceedings came before the judge, he was told the sentence warrant had not been found. During the hearing, a fresh warrant was sought and secured from the District Court.
Senior counsel Martin Giblin, for Walsh, argued that Article 40 proceedings could not be used as a basis to detain someone while an effort was being made to secure a warrant to provide a legal basis for their detention.
The judge upheld Walsh's challenge and directed his release. Counsel for the DPP said there would be a new bid to secure the detention of Walsh to complete the term imposed on the assault charges.