The European Court of Human Rights has rejected Colin Duffy’s legal challenge over his arrest in connection with the Massereene barracks murders in 2009.
Strasbourg judges ruled inadmissible an application by Duffy, who was acquitted of murdering Sappers Patrick Azimkar, 21, and Mark Quinsey, 23.
Duffy’s claims focused on measures in the Terrorism Act 2000 which allow police to keep terror suspects in custody for questioning for up to 14 days.
The soldiers, who were due to fly out to Afghanistan the following day, were gunned down in a 30-second hail of gunfire as they collected pizza from delivery drivers outside the barracks on March 7, 2009.
More than 60 shots were fired and, after the initial burst of automatic fire, the gunmen walked over to the wounded soldiers and fired at close range.
The shootings shook the fragile peace process in Northern Ireland and were the first British military fatalities in the province since Lance Bombardier Stephen Restorick was shot dead by the Provisional IRA in 1997.
In Duffy’s trial before a judge sitting without a jury, Antrim Crown Court heard his DNA matched that found on a seat belt buckle and on the tip of a latex glove discovered inside a burnt-out Vauxhall Cavalier used by the killers to flee the murder scene.
Mr Justice Anthony Hart said he was satisfied the DNA had been found in the car but said the prosecution had failed to link the defendant to the murders.
Ministers faced the prospect of having to re-write the counter-terror legislation if the Strasbourg challenges had been successful.
Duffy was jailed for life in 1995 for shooting dead a former Ulster Defence Regiment soldier, John Lyness, but the conviction was overturned the following year.