Interesting article that says that those "warranty void if sticker removed" stickers are illegal:
Does anyone know what the situation in NZ is?
neb: Not sure about the legal situation, but the vast majority of tamper-indicating stickers and seals can be removed with naptha and later reapplied with no signs of tampering indicated. So you could do an end-run around the problem...
Here's a sample of some tamper-indicating seals that have been removed and reapplied... by a ten-year-old kid.
Image from Locksport Canberra, work done by one of the kids of the couple who were running the tamper-evidence hacking table.