Personally, I think any child stupid enough to stick his fingers thru a fence deserves to get bitten.

I would think that it would be the fault of the parent for not watching the child, and for not making sure the child knows NOT to go sticking its hands thru fences with dogs on the other side. Of course, we are talking about the country where if I robbed your house, fell and hurt myself, I could sue YOU and WIN. To be on the safe side, I would try to put something up that would prevent him from sticking his fingers thru. If he managed to do it anyway, it would show that you would have at least tried to fix it so he couldn't. It should then go back to the parents.

Not much help, I know... sorry...