Saying the same thing over and over again doesn't change a thing, or make it right.

Maintaining prohibition is not going to make organised cannabis growers go away no matter what sentences you threaten them with, in the same vein as telling people of the risks associated with using heroin and cocaine "cut" with who knows what chemicals is dangerous, will stop people from using these substances.

Quite the contrary in fact. By enforcing the illegal status of cannabis the police are actually encouraging organised criminals by bolstering the market.

This is a really simple equation. Organised crime, minus crime, equals no organised crime, as is the case in Holland, in Belgium and in Portugal. 

By taking cannabis out of the hands of criminals and regulating its supply at government level, these cannabis farms will go out of business, almost overnight.