Bougainvillean, Scott Dylan, has been convicted this week by the Papua New Guinea National Court of the illegal possession of a high powered police issue firearm.
He also had ammmunition and a pair of police uniforms.
A senior police officer is thought to have illegally issued the equipment so Dylan could serve as a security guard for a private company.
Dylan claimed he was a police reservist and had pleaded not guilty to the charges, but the court found he was not associated with the police in any way.