PLAID Cymru has renewed calls for Wales to have complete jurisdiction over the criminal justice system.
Party leader Leanne Wood, who used to be a probation officer, said it would help the crackdown on drugs.
Her call follows the publication of a House of Commons Select Committee report on breaking the cycle of drug addiction.
The report by the Home Affairs Select Committee recommended greater links between the Home Office and the Department of Health in dealing with addictions and illegal substances. Plaid Cymru argue that this must mean a role for the Welsh Government and the introduction of a more effective and evidence based approach to drug policies, providing support and treatment for users and targeting policing resources at the top-level dealers and those who control the illegal drug supply.
The full devolution of criminal justice to Wales would allow us to adopt a, progressive, Welsh approach to the drugs issue — an approach that would achieve better results, a party spokeswoman said.
"This report from the Home Affairs Select Committee recommends that the Home Office work with the Department of Health, recognising that addictive substances are just as much a matter for health and society in general as much as for law and order enforcement agencies," Ms Wood said.
"In Wales this means a role for the Welsh Government.
"It would make sense for there to be a more progressive, evidence-based approach taken in other social issues in Wales to be adopted on this as well.
"I worked as a probation officer before my election to the National Assembly for Wales. I drew on that experience in the publication of a detailed paper aimed at making our communities safer.
"I argued for an alternative approach — saying that we need a long-term multi-agency strategy which treats problematic drug users as patients rather than criminals.
"I also argued for strategies that focus on harm reduction for individuals, families and communities, including for victims of crime.
"Health resources need to be focused on people while law and order resources should concentrate on stopping and catching those who profit from other people's misery."
The leader also gave her backing to the establishment of a commission into drugs.
She said: "A commission on drugs, with a wide remit to look at the effects that they have on society, is well overdue."