I don't smack, because I don't need to (and DS loves having his bum hit). If ANYONE, no matter who, EVER hit my child for WHATEVER reason then I'd wallop them one. And I have a mean left hook.

My parents smacked, but they were the only ones allowed to do so. My mother's little sister is a prize one, she really is, and she hit me once. My Dad saw and walloped her back. That's the stance I would take regardless of if I smacked or not.

Mum wouldn't smack anyway, she's seen how other methods work (both with me when I was little and with DS) so knows it isn't needed. MiL... chance would be a fine thing! She doesn't like DS (or me, or whatever, I'm beyond caring) so never sees him so I don't know what her policy would be if she ever responded to our begging for her to play with DS for up to half an hour as I am physically unable. FiL does if I'm hospitalised and is great with DS, but it is for VERY short periods of time only and DS is very well-behaved with him as he doesn't know him too well.