I remember reading a piece Clive Rees wrote about a lady who had puppies with docked tails, unfortunately for her she admitted it and was charged but i think the general gist of the piece aimed at if she'd said nothing and admitted nothing it was a case that would have been hard to prove. The other scenario given was she may well have bought the litter already docked, how then could she be charged ?
I guess some of these situations could be applied to freeze branding.