Legalise cannabis and tax it, sounds dead easy but it isn't only cannabis that is the problem.
No, it's not the whole problem, but it is a big problem. And it's all about marketing - drug dealers are excellent salesmen.
e.g. if somebody wants some cannabis, the only way to get it is to deal with a drug gang (or try growing it without being caught, but ignore that).
they will soon develop a relationship with a drug dealer, as they will likely see them every week. The dealer will then push other drugs that are more lucrative on to them - they'll do the old "out of cannabis, but can offer this at a big discount for you this week" trick. That works. Soon a person is into the hard drugs. Their lives start to fall apart at this point.
Alternative reality: somebody wants some cannabis, so they go to their pharmacy and buy it through a prescription based system giving their name and address, linked to GP records. They will never have anything else pushed on them, and if they start using more, advice can be given at the point of sale and GP records updated.
I follow the local police social media pages and much of what they confiscate from dealers is cannabis. It is a drug that many new dealers deal before dealing the harder drugs.
Legalising it won't make drug crime vanish, but it will hit the gangs so hard that they will no longer have such a large territory that they need to control, many dealers will effectively go out of business and will have to take up some honest work instead. Might all sound a bit like a fantasy, but it does work (help) in other countries, so no reason why it wouldn't work here too.
And it really is not very different from prohibition in America - banning alcohol led to a massive growth in organised crime - people we're already addicted to that drug so would happily break the new law to get hold of it.
Some further reading
https://www.adamsmith.org/research/...uce-crime-protect-children-and-improve-safety