The Colombian attorney general's office has appealed the acquittal last month of three Irishmen it accused of teaching bomb-making to Marxist rebels.
Jim Monaghan, Niall Connolly and Martin McCauley will not be allowed to leave Colombia until the appeals process runs its course, a spokeswoman for the attorney general's office said.
If the case reaches the Supreme Court this could take as long as five years, according to legal experts. The three men are refusing to leave a Bogota jail until the government provides them with protection against far-right gunmen who kill those they suspect of sympathising with the rebels.
A judge last month dismissed the state's bomb charges, which were based on circumstantial evidence and testimony by alleged rebel defectors.
But the men were sentenced to between 26 and 44 months for using false passports during their 2001 visit to a southern stronghold of the Revolutionary Armed Forces of Colombia (FARC).
They have already spent 33 months behind bars, and their lawyers say they can leave prison for time served or on parole once they pay a fine of about €6,000 each.
But the men's representatives say they will not leave Bogota's Modelo prison without protection. So far the government has refused requests for a safehouse and bodyguards, the representatives said.
The attorney general's office promised to appeal within minutes of the April 26th ruling.