On the contrary, you prohibit exactly "unlawful <sort of action>", e.g. "unlawful consumption of narcotics". That means that what exactly constitutes unlawfulness of such acts is a part of a different law, and usually not even a law, but a by-law or a regulation.

For example, look at the German penal code, title 184f, "Ausübung der verbotenen Prostitution" — it's literally "Practicing illegal prostitution", and it's worded that way because there is also legal one.

If you just say "prohibit trade of wild animals", that would imply China just outlawed all trade related to wild animals while the news is actually about a decision to absolutely enforce existing laws.