Mailing baking powder--arrested for what?

I’m sure that there is some legal principle ensuring that what the guy did is indeed illegal. It just never struck me before that the law could be so subjective.

I wonder what might happen if there is a scare involving some other disease. If smallpox were somehow released, kids who haven’t taken their Noxema had better watch out (lest they cause a panic while they’re walking down the street).