Cannabis should be legalised.

Most of the problems we see from drug use, either those caused to the individual or society, come from prohibition itself. Prohibition makes it harder for people in trouble to seek help. It makes it harder to communicate the dangers of drugs to drug takers and it creates a fantastically rich class of gangsters who will kill to protect their turf.

The problem with finding them and punishing them is that it extremely expensive, as is widely known because finding and punishing them is exactly what we are doing now. After 70 years of supply side intervention, drugs are still widely available and drug dealers are still here. The US has more prisoners per capita than anywhere in the world. You simply cannot lock up all the drug dealers and throw away the key. Where there is a great demand you will always find people willing to risk supplying it.it. 
 
The American history during the period of "The Prohibition" (of alchohol) in the 1920's clearly shows how prohibition can increase the demand of a popular item. If people really want it there will be people risking to supply. This will result in black market violence between gangs for control of the supply and further enhance difficulties for people in need of help to seek it out.

Drugs cause huge problems and the answer is not simply to throw up our hands and abandon our young to the ravages of substance abuse. Prohibition might not be working in its present form but it is unacceptable to give up. And we definitely should not abandon a law because it makes gangsters rich. Instead we should find them and arrest them and punish them in such a way to dissuade anyone considering this a career path.