Trudeau'd rather let opioid users die in droves(from unregulated black market drugs of dangerously uncertain content, strength, and dosage)than politically risk riling irrational,hypocritical,druggie-hating redneck sentiments he knows are all too common among voters, including  many "progressives".He&his advisors have likely done a cold political calculation they don't want to go TOO far along the drug laws reform road beyond legalizing cannabis for fear of a redneck backlash. 

It's prohibition laws that make black market drugs more dangerous than they otherwise would be. Many of the arguments Trudeau uses to justify legalizing & regulating cannabis also apply, rationally, to other popular drugs. In fact, from a life saving standpoint,there's MORE urgency to legalize&carefully regulate opioids&sell them in standardized doses as so many lives would be saved by doing so. In contrast, few if any cannabis users' lives are at risk from using black market cannabis.End the homicidal drug war