Police say about 10 criminal charges against several people have been dropped because the officers involved in the cases were not sworn-in properly.
The charges included possession of cannabis for supply, selling cannabis, burglary and receiving stolen goods.
One officer from Wellington district and one from Counties Manukau have been placed on restricted duties and an investigation started into how they were deployed without proper authorisation.
Superintendent Richard Chambers said he's very disappointed as it is the third time since the Policing Act was passed in 2008 that there have been problems with the swearing in of officers.
Last year, parliament had to pass legislation under urgency to validate an administrative error by the police over the swearing in of 63 returning police officers.
Police Minister Anne Tolley said the situation was simply not good enough.
Ms Tolley said this is a basic but important task and police need to get it right every single time.