Its a bit of a iffy situation in nz with the gecko's now. We hand a license to keep them and now you cant get license's to keep them and our license has expired, so we have fallen into a black hole with the legality of keeping geckos. Our green gecko's just keep breeding and are not the easiest things to look after in regards to food.
The reason that some exotics have been banned is what would happen if that snake you had escaped and started to eat native wildlife? There are any examples of exotic wildlife destroying native bush and killing of other animals around the world....for example the Possum here in New Zealand