I cannot see how this law may be policed! Apart from thinking it is ludicrous, it would need every parent to be shadowed by the smacking police...
In an age when kids seem to dictate how they should be treated about the only thing left for parents is a swift smack on the bottom at the time of the 'offense'. It is necessary in certain situations in order to reinforce the NO word. How else can that be done?
I know I am probably old fashioned but I believe that a child needs loads of cuddles interspersed with a few smacks.