The police watchdog has found the use of pepper spray against a man, and his subsequent arrest in Porirua last year, were unlawful.
The Independent Police Conduct Authority has ruled that officers had no lawful power to stop the man getting out of the car he was travelling in after it was stopped by police on a petrol station forecourt.
Police had pulled the car over after one of the four passengers in it yelled an obscenity at them.
Once parked, the front seat passenger began to walk towards the petrol station shop to buy cigarettes.
The police officer repeatedly told the man to get back into the car but he ignored the order.
A scuffle broke out and the officer pepper-sprayed the man and arrested him for obstructing the police.
Police say mistakes were made during the incident, which they can learn from.
All charges laid against the man were subsequently withdrawn.