In New Zealand ferrets are illegal to keep as pets. For good reason.
There were first brought here, in the eighteenth century, to keep rabbits in check, but they just kept arriving, multiplying and became a significant danger to native birds.
Apparently, over in the States, the New Zealand example is often pointed to as why Californian residents shouldn't be allowed to keep ferrets. There's a passionate community of ferret-lovers in the golden state, who see the issue as one of excessive and illogical lawmaking.
La Masa resident Pat Wright, of the Legalise Ferrets group, spends around 30 hours a week on the issue and has even served time in maximum security prison - such is his passion.