Heritage and in particular, archaeological sites are protected in New Zealand under a range of laws. The most obvious is the Resource Management Act (1991) with heritage considered a matter of "National Importance" under Section 6 of the Act. The specific Act protecting archaeological sites is the Heritage New Zealand Pouhere Taonga Act (2014).
Under these laws, any site or structure which has seen occupation by humans prior to the date of 1900 is protected by the legislation and requires a special permit or Archaeological Authority prior to works commencing. These permits are granted by Heritage New Zealand, the governing body who manage the implementation of the legistlation.
Please note, just because a property or structure is not on the Hertiage New Zealand List, does not mean it is not protected.