That would be very foolish on their part, in that most of the Fentanyl and Carfentanil stays in China and the region. They have recently outlawed its production, but for the same reasons it took the US a long time to outlaw designer drugs. There are just so danged many of them.
Here is a very useful table that should be bookmarked for later. Equianalgesics. That is, with oral morphine as the baseline as “1”, other pain relievers are either fractions of “1”, like aspirin at 1/360th of the strength of morphine. Or in the other direction, Carfentanil, which is 10,000 to 100,000 times stronger than morphine.
https://en.wikipedia.org/wiki/Equianalgesic
The most potent drug on the table that is legal for human use is Fentanyl, 50 to 100 times stronger than morphine. Everything above that is very illegal.
Importantly, this table only shows *the most common* of the drugs. There are literally thousands more that *could* be on the table. Many don’t even have names, just numbers. And more are being invented all the time.
How do you outlaw something that hasn’t been invented yet?
We might be having the right idea to just declare any drug more potent than Fentanyl as being a Weapon of Mass Destruction.