I suppose the analogy from the Prohibition would be that bootleggers, distributors of Alcohol etc.  moved to other lines of business - e.g. narcotics, protection rackets - and so hard drug dealers might just move elsewhere in the crime business if drug pushing became unprofitable and they had no legit options.

People with an alcohol dependency during the Prohibition who committed crimes to support their habit might also continue to do so if "decriminalisation" did not result in a significant reduction in price, although if drinking itself was no longer part of a criminalised subculture then this might be less likely.

Obviously if heroin is available free on prescription that ceases to be an issue.  But what if a doctor refuses to prescribe heroin because he believes that doing so is not in the best interests of his patient?   Most doctors I know in the addiction field are already at grave risk of assault, break-in etc. if they do not prescribe what their patient want.  Some take the soft option.

Index of Frank's Diaries