Policy should be evidence based.
The Cochrane Library have recently published a review of the evidence on prescribing heroin (diamorphine). What did they find?
According with the current evidence, heroin prescription should be indicated to people who is currently or have previously failed maintenance treatment, and it should be provided in clinical settings where proper follow-up is ensured.
Treatment practices should always be updated to reflect the evidence. Policy that gets in the way of making these changes is bad policy.