Earlier quoted context omitted.
I don't believe Portland's efforts caused the rise of fentanyl, though. How do we know it wouldn't be worse, if not for Portland's efforts?
My recollection is that in 2007 Mexico banned pseudoephedrine in order to remove feed stock from meth labs supplying the US.[0,1] As a result of this and other factors suppliers in Mexico found fentanyl, which bypassed growing cycles of agricultural drugs like pot and heroin. During the pandemic, Mexico grew additional trade ties with China which included fentanyl precursor chemicals.[2] 0. https://www.reuters.com/ar…
Opioids being more dependence-inducing than stimulants would better explain a production shift.
Big legitimate trading volumes with China (and any other large producer of goods/inputs) make a customs-focussed effort at controlling supply basically impossible.