If you live in a social democracy with universal healthcare, drugs policy should probably be based around harm reduction. This is why helmets are required on bicycles (in some countries, for better or worse) and you need to wear a seatbelt in the car.
It's your body, but the public has to pick up the tab when you break it.
I don't think that you should be able to go to the pharmacy and buy heroin or methamphetamine off the shelf. The potential for abuse is too high.
However, as I said, people will find drugs if they want them. If I wanted to buy some heroin, I could find some within 30 minutes just walking down the street. I really don't know what the solution is.
It's not the most addictive drug around. It's not at all the most dangerous. It's not all that much more damaging than a lot of other drugs we're happy to let people take.
Almost all of the worst damage caused by heroin today is caused by treating it as a criminal justice problem rather than as a public health issue. If people could seek medical advice safely, could get clean drugs, could get alternative forms (e.g. a lot of people end up injecting heroin because oral oxycodone is too expensive on the black market once they get cut off from their prescriptions), it would not solve all of it, but it would solve most of the problems.
So start there if the problem you want to solve is the cost to society. Heroin is mostly a politician-created problem, and at this point there is sufficient knowledge that frankly I consider any politician still supporting the continued prohibition of it morally equivalent to mass murderers. They are knowingly making decisions that kill people in large numbers.
To the extent there still is a problem after legalising these drugs, look at actual health-focused interventions, rather than turning people with a health issue into criminals.
Drug legalization is about using public funds on other issues besides individual drug users, reducing prison populations for non-violent drug offenders, offering those in need treatment instead of incarceration, removing an income stream for gangs
Why do you need prisons when people will voluntarily imprison themselves?
It's not obvious to me. The fundamental question is, does an individual own their own body? If the answer is yes, then don't try to restrict what I can do with it so long as I don't harm anyone else. If the answer is no, well, then we need to firm up exactly what the arrangement is supposed to be.