Those who break the law while abroad are usually convicted and punished in that nation. There may be a prisoner exchange agreement between nations, but how often does that happen.....
Well we could trial a system where the kiwis get to keep their crooks AND we send all the rest of them back over there as well...what is a few thousand extra expat peds, rapists, murderers, and assorted filth to the kiwis.
That ardern horror would gladly take them in and provide succour.