It is not possible to stop people from getting mail order pills from China. Especially with the abortion restrictions the market already is pretty large and it will be easy for them to throw these drugs in too.
We used to believe it was not possible to stop people from getting their funny movie clips from China.
The solution to that was a $10 per month subscription via Netflix and clips for free on YouTube. Meanwhile Ozempic is around $1,000 for a month's supply. That is a margin on par with illegal hard drugs, which already have a smuggling supply chain from China to North America (eg. Fentanyl and variants).