If you intend on your car remaining road legal:
http://www.ltsa.govt.nz/certifiers/virm-in-service/general-07-v3a4.pdf
Page 33
A motor vehicle that has had an airbag removed or made inoperable must either:
a) have all OE signs lights, or other devices that indicated the vehicle was fitted with an airbag removed, or
b) if the signs, lights, or other devices cannot be readily removed, have a label that indicates an airbag has been removed permanently attached in a prominent location where it is clearly visible to any occupant of the seating position that was previously protected by the airbag.
9. A modification that affects an airbag system must be inspected and certified by an LVV specialist certifier, unless the vehicle is:
a) excluded from the requirement for LVV specialist certification (Table 7-6-1), and
b) has been inspected in accordance with the requirements in this manual, including those for equipment, condition and performance.