You violate the law when you infringe regardless, but intent matters for determining the penalty for doing so. The law basically says that, specifically for in

You violate the law when you infringe regardless, but intent matters for determining the penalty for doing so. The law basically says that, specifically for infringing a copyright, doing so out of ignorance is less punishable. Ignorance isn't a general defense, but some laws do account for it on a case by case basis.