2paragraphs from the ruling in Gonzalez v. Santa Clara County Dep’t of Social Servs. (Cal. Ct. App. Oct. 8, 2013):
We cannot say that the use of a wooden spoon to administer a spanking necessarily exceeds the bounds of reasonable parental discipline. Although no published California decision addresses this issue, the Attorney General has concluded that “[i]t is not unlawful for a parent to spank a child for disciplinary purposes with an object other than the hand,” provided that “the punishment [is] necessary and not excessive in relation to the individual circumstances.” Opinions from other jurisdictions preponderate to similar effect.
Nor do we think that the infliction of visible bruises automatically requires a finding that the limits of reasonable discipline were exceeded. Certainly the presence of lasting bruises or other marks may support a finding that a parent crossed the line between permissible discipline and reportable abuse. However, such effects alone do not compel a finding of child abuse.
–more commentary at The Volokh Conspiracy