In New Zealand, trap use is regulated by the Animal Welfare Act 1999. This Act permits any trap to be used for trapping any species, but it also enables the Minister of Agriculture to recommend to the Governor General traps that should be prohibited because they cause unacceptable pain and suffering.
The National Animal Welfare Advisory Committee (NAWAC) was established under the Animal Welfare Act to provide independent advice on animal welfare to the Minister for Primary Industries.
One of their roles is to provide the Minister of Primary Industries with advice on traps and devices. To this end they have approved certain traps/devices — see the full list here. Note: traps do not need to be NAWAC-approved to go on sale, so some traps legally for sale may be less humane than those that are NAWAC-approved.
Traps known to be particularly inhumane (for example, the Lanes Ace gin trap) are banned from sale or use.
Toxins and baits must be used according to their label and approved by Ministry of Primary Industries (MPI).