I say spank them if you to.
Sometimes my girls won't listen at all. I tell them 190 times not to do something and they keep doign it, even with putting them in "time-out" or putting them to bed. As soon as they get up they go right back at it. Sometimes, being spanked is the only thing that can get through to them.
WV CPS says as long as it's open handed swatting on the behind without leaving marks it's ok to do. WE don't leave marks and bruises so, I see no harm in it, if nothing else will work.
On another note, the bible does say, spare the rod, spoil the child. Even though I am not a church going, bible thumper, I do believe in the saying.