Civil liberties advocates say they worry that police could use a newly-bought drone to illegally spy on people.
The police bought a small unmanned aircraft - similar in concept to those used in overseas military operations - after hiring a company to provide a drone in two investigations this year.
The drones hold cameras and the police are looking at whether they will be useful in future operations.
But Global Peace and Justice spokesperson John Minto says the police should be careful, as they have abused their powers with new technology before.
"Inevitably, the lines get blurred," he says.
Mr Minto says there have been several occasions - such as the illegal surviellance of people in Te Urewera raids case - where the police have overstepped the mark and ignored the law.
The police drone has not yet been used, but police say the technology could save money, as an unmanned aircraft would be cheaper than using a helicopter.
The cameras take still and 3-D photos, video and infra-red images at night.
The Council for Civil Liberties says it hopes police will obtain search warrants if they use the drone to spy on private property.
Spokesperson Kevin McCormack said there should be rules on its use - whether it is flown over public places or private property.