The public are already reporting gang patch sightings a day after the ban began.

New Police powers let officers disperse gatherings, and gang insignia is banned in public.

More than a dozen gang members have already been arrested under the new law - including an Auckland Head Hunters leader.

Assistant Commissioner Paul Basham told Heather du Plessis-Allan they're being informed about breaches in multiple ways.

“We’ve said that when this sort of stuff comes through, we’ll follow it up as quickly as we can, and today’s search warrant is a case in point where something was reported in the early hours after the law came into affect.”

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