It is illegal here in NZ, which I think is wonderful.
It has been since 2007.
The law is not one of anti-smacking, simply that assault of any person is illegal, and as we all know "a person is a person, no matter how small"
There is a HUGE emphasis on teaching parents from the word go about discipline and guidance methods which do not include violence, and children are taught at school, by their teachers, that they are not allowed to be hit.
It is seeping into the culture from the ground up, children know their rights very clearly. Awesome stuff.
There have not been loads of parents put into jail. Parents still take their kids to the doctor and hospital for accidents, it's not a huge deal.
I'm sure there are still parents who smack, but it is no longer socially acceptable, or lawful, and that is a huge step forward.
It will be interesting to see how far out of the culture smacking has moved in say 20 more years with these laws in place.