One very important reason to legalize access to opioids is for quality control. The main reason why overdoses occur is because street drug potency is unknown,

One very important reason to legalize access to opioids is for quality control. The main reason why overdoses occur is because street drug potency is unknown, and because street drug potency can be inconsistent within the same batch. (IE, if my black market "heroin" is really powdered fentanyl mixed in a gel, if I don't mix it well the fentanyl will clump, and the clumps could kill someone.)