Fire Police gain their special legal powers through legislation; Currently the Fire Service Act 1975.

Whilst Section 28 of the Act defines the 'functions, duties and powers of a Chief Fire Officer' and is the legal justification for most of what the New Zealand Fire Service's rights under law, there is another clause (Section 33) of the Act which allows for the formation of a volunteer Fire Police unit by a Chief Fire Officer, with the approval of the Police Commander for the district. Fire Police are sworn as Constables by a Justice of the Peace and when on duty, exercise the full legal powers of a Police Officer.

The text of Section 33 is as follows:

33.Volunteer fire police—

(1)With the consent of the senior officer of the Police in the district, any Chief Fire Officer, in accordance with the policy of the Commission, may establish a volunteer fire police unit and enrol any person as a member thereof and may in like manner disestablish such a unit or for just cause remove any person from the roll.

(2)Every person enrolled under this section shall be sworn in before a Justice of the Peace, and during the period of his service as a member of the fire police and while so acting shall be deemed to be, and shall have all the power and authority and responsibility of, a constable.

(3)In the performance of their duties at any fire or other incident to which a fire brigade is called, volunteer fire police shall carry out their duties under the direction of the person in charge of the fire brigade.

Fire Police, as members of the New Zealand Fire Service, also gain all the powers held by the Chief Fire Officer (as delegated),per Section 28 of the Act. These powers are quite substantial, and provide sufficient powers to take all actions required in the interests of public safety during a Fire or Other Emergency. Section 33 as decribed above amplifies those powers and clarifies them in the direct context of the duties that Fire Police perform.