In my opinion, marijuana's ease of production renders law enforcement efforts useless, and pointless. Because marijuana is an agricultural product and not a manufactured product or a product that needs to be refined in a laboratory like environment it is far more difficult to enforce prohibitions upon it. Also the fact that it takes months to bring a crop to maturity and harvest also shows law enforcement to be impotent.
Seeds , soil, and sunlight (or growth lamps)
Anyone can grow pot. From a single seed an entire crop can be created. Its a hardy plant, does not take expertise to grow or harvest. There is no criminal organization, central production facilities necessary for this drug. You could say this is a "grassroots" drug in that production can be local everywhere. People who want to get it are going to get it. There is no point putting people in jail as the economic incentive is too high and market too large. Supply and demand economics, there will always be someone willing to act as supplier as long as there is demand and there is little reason to think that the demand for pot will be disappearing. Better to educate, regulate, and tax