> Heroin for example is a serious threat for physic and mental health isn't?
Heroin is comparable in risk profile to morphine, and is significantly weaker than fentanyl, both of which are frequently prescribed for pain management. Most of the risk of use comes from addiction, which causes other risky behaviors, and contamination. Both of these risks are poorly-mitigated by criminalization of heroin: addicts rarely want to be addicted, but have difficulty seeking help due to criminalization and social stigma, and contamination would be preventable if heroin were manufactured in regulated facilities.
Uneducated and influenceable people currently consume heroin, not realizing their act. The war on drugs has done nothing to prevent this, and in fact has made it harder for people to find real information on heroin. A regulated product could have messages printed on the packaging similar to the way that cigarettes currently do.