The judge described the Security Services’ operation as an “elaborate and successful” hoax.
The trial was the first for 20 years in which MI5 agents gave evidence in a Belfast court.
McCaugherty showed no emotion and occasionally yawned as Mr Justice Hart, sitting in a Diplock, no-jury court, delivered his verdict.
The judge rejected claims that the defendant had been “induced or entrapped” by an undercover operative called “Ali” during meetings across Europe including in Amsterdam and Instanbul.
He said that although the covert operation had been an “elaborate hoax” it did not mean he had to acquit the defendant.
McCaugherty, the judge said, had taken advantage of the opportunity, and even if he had been presented with a real arms dealer he still would have committed the offences.