Karetu was arrested in March after the covert investigation Operation Yellowstone targeted an Auckland businessman selling commercial quantities of methamphetamine.
Karetu, who was living in Tauranga at the time, was one of his customers. A police search of his home uncovered a 9mm semi-automatic pistol, a cash counting machine, and $68,100 inside a Louis Vuitton handbag.
Encrypted messages showed Karetu purchased 1kg of meth for $140,000 at one meeting.
As the national president of the Mongrel Mob Barbarians, Karetu used his status and criminal connections to distribute the drug around the North Island.
Karetu pleaded guilty to offering to supply, supplying, and possession of a Class-A drug for supply, unlawful possession of a pistol, and possession and supply of synthetic cannabis.
He was due to be sentenced in the Manukau District Court next month.
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