From the Arms Code (2013)
https://www.police.govt.nz/sites/def...-code-2013.pdf
That's the official version.
The law is an arse.
How well will it work if you need to go to the bank (or cafe) on your long trip?
You take your firearms soft or hard case with you.
The bank won't let you in.
Nek minute the AOS come racing around the corner .....
A practical, but illegal solution is to always take your bolt(s) with you when you leave the vehicle.
Then, at least, you're leaving an inoperative firearm in the locked vehicle. Cover/hide the firearm too.