Like Iam64 I would only legalise certain drugs like regulated types of cannabis, and not heroin, crack cocaine, methamphetamine, ecstacy etc, which are generally damaging because of their link to offending, prostitution, some dependence, and degeneration of health, lifestyle and prospects for users and their dependent families.
I have known just as many professionals as offenders who use cannabis routinely. Used wisely, it brings relaxation, pleasure and pain relief, but it needs regulation in order to screen out the more problematic skunk, which is linked to mental health problems for some users. Large scale secretive growing in houses would be drastically reduced if cannabis was legalised, and regulated cannabis farms could provide some employment.
Drug dealers know that supplying cannabis brings them access to potential users of stronger drugs, so separation from street drugs would isolate dealers from those contacts. Treatment programmes to deter dealers from further offences have a degree of success, but the profit gained from dealing to addicts who share and sell small amounts cannot compete where employment problems persist. There would still be the problem of drug smuggling and gangs controlling illegal drugs, which needs tackling on a global scale.