Dr Rudolf Peitel, HMP Holme House
Dr Rudolf Peitel, who worked at Holme House Prison, in Stockton, was convicted in 1993 of trying to bring firearms into Germany from Pakistan.
Peitel, 57, later came to the UK to practise and took on roles through an agency.
The hearing concluded yesterday that the convictions meant Peitel's fitness to practise in the UK was impaired.
He was suspended from the medical register after the hearing yesterday.
The court heard how Peitel arranged for the gadgets - a single-shot gun that looks like a pen used by spies and assassins - to be posted to the home of a friend in Germany.
But Peitel was arrested and five ball-point pen guns were intercepted after he was reported to police. Peitel escaped with a fine of DM12,000 (£3,800) in June 1993.
Three years later, the father-of-one received a six-month suspended sentence after attempting to con a business partner out of DM55,000 (£19,000).
