A new study from Canada finds that treating heroin addicts with heroin is more effective than treating them with methadone (a synthetic opiod). Effectiveness is defined as how long participants stay in treatment.
Well, of course! If heroin users can get free heroin from a clinic, and avoid the risk of arrest, they will do so. These users will be more likely to continue heroin treatment than methadone treatment because heroin is regarded as the better drug. If clinics offer free, single-malt scotch, then "users" will stay in "treatment" more than if offered rot-gut.
The study does have an important result; it confirms again that people can use heroin for extended periods and still function normally, if they have access to a legal supply with known purity. This fact was widely accepted before the U.S. prohibited opiates in 1914; the favored treatment for opiate addiction then was maintenance, meaing legal provision of opiates.
The best way to give heroin users access to cheap, high-quality heroin is to legalize. This eliminates both the need for government clinics and the adverse consequences of prohibition.