Why was she arrested by the customs?

I am a foreigner writing to you to inquire about your territory's law and regulations. Where can I find the list of forbidden items restricted to bring to Shenzhen? According to this website, the list appears non-specific; for example, food, drugs or other things that could do harm to humans and animals, and are infectious or from epidemic areas. In this case how do I know that my product is considered a harmful item, like snake gall? According to online blogs and reviews, people consider snake gall as medical treatment or supplement that nourishes their health. How can I know that in Shenzhen it is forbidden to bring in.

Importantly, my aunt got arrested at Shenzhen airport last month due to the reason that she brought snake gall to Shenzhen in July. She didn't know that it was illegal. In November she went back to Shenzhen again for traveling with my grandma, but then the police arrested her. As a foreigner, I see no fairness that Shenzhen regulations do to her this way. If it was illegal, why did the police not arrest her the first time? Should they not warn her to let her know snake gall is considered illegal? Please understand that it is not harmful or additive drugs. If they do that, please be sure to clarify the reasons. Why just arrested her the second time when she is with her very old mother?

Respectfully Yours,
Sue