The iron law of prohibition states that, all things being equal, as enforcement ramps up, smugglers prefer higher potency forms of a drug for the same reason those who sneak alcohol into a football game prefer hard alcohol in flasks to 12‐packs of beer. The lethal logic of the iron law of prohibition means that we cannot enforce our way out of the opioid crisis. And if fentanyl smugglers become somehow easy to catch, there’s always carfentanil, which is about 100 times more potent than fentanyl and has already been showing up in America’s drug supply.
https://www.cato.org/blog/dea-seizes-record-amounts-fentanyl-2022