More than 50 people were arrested in Operation Notus following a six-month investigation into alleged methamphetamine supply in the eastern Bay of Plenty.
In court, Judge Mabey said the Operation Notus inquiries discovered "substantial drug activity" involving intercepted communications including text messaging.
It became clear during the inquiries Drummond's involvement was "substantial" in the cultivation and distribution of cannabis and methamphetamine, he said.
Drummond had said he got involved to help his son, who was also charged, to repay a debt to the Mongrel Mob, Judge Mabey told the court.
Judge Mabey also did not accept the "untimely" death of Drummond's wife, his age, and health led him to the drug activity.
"You voluntarily became involved ... You did so because you chose to and still do not think there is any harm in it."
Judge Mabey gave Drummond a 20 per cent discount for his earlier guilty plea and sentenced him to five years and two months' imprisonment.
