[rsynnott]

The drug dealers were British subjects, in general. China didn't have an easy way to punish them (the actual merchants responsible generally wouldn't be entering China), but Britain absolutely did, so could enforce its own laws against opium (which were then fairly strict; it would've been a death penalty thing). Britain _did_ have an opium problem, incidentally, but the volumes imported were just much smaller.

Opium was produced in British India, not China, for the most part.