Norway recently legislated for Portuguese style decriminalisation of drug use. Dealing hard drugs will still be illegal and dealers will still be pursued, but drug use and the behaviours typical of addicts will no longer be treated as criminal matters but as public health issues. This approach has had a massive effect in Portugal, dramatically reducing use rates, medical complications from drug use and related crime.
Obviously Norway is a different country from Sweden, but do you know what made them go down that route? Do they have a significantly bigger drugs problem there?
I live in Stockholm and there is pretty much no heroin here. Don't let people say "there is", there's not. Compared to any large european city, you never see strung out junkies anywhere.
I would love to know how much of the crime difference between a city like Dublin and Stockholm can be explained by heroin (just heroin - we don't have much crack or breaking-bad stuff). I expect it's the majority of crime and definitely the majority of homelessness. Heroin is like a viral infection. If it appears in a city, you have to quarantine off that area, clear the infection or it will spread and then it's just chronic management after that.