You don't really need regulation to get consistent strength/purity, branding (Buy Mack's Heroin - guaranteed 99.99% pure with no adulterants!) and tort law (you

You don't really need regulation to get consistent strength/purity, branding (Buy Mack's Heroin - guaranteed 99.99% pure with no adulterants!) and tort law (you said this contained 20mg of heroin, it contained, dangerously, twice that amount, you are liable for my consequent overdose) should be enough to handle that, if producers were competing on quality and not "ability to operate in a black market".