Under international laws, cultivation, supply and possession of cannabis should be allowed only for ‘medical and scientific purposes’. In general, possession of the drug for personal use should be a crime, to deter use, and most countries make this punishable by imprisonment. In recent years, however, several jurisdictions have reduced their penalties for cannabis users, and some have permitted supply of the drug, allowing us to observe different control models and their consequences. Policy discussions are complicated by conflicting claims — decriminalisation or legalisation, medical or recreational use, policy success or failure — and this page aims to clarify some issues.