Proposition 19

In November, California’s voters will consider Proposition 19, which would legalise possession of up to an ounce of the drug for personal use. Harvard economist Jeffrey Miron, a veteran proponent of legalisation, has estimated it would generate up to $7billion a year in revenue, while saving $13billion in law enforcement and prison costs.

Governor Arnold Schwarzenegger announced that “it’s time for a debate” last year, and with the freedom of a film star whose time in office is almost up, told journalists he has frequently enjoyed smoking marijuana. According to a recent poll, Californians who disapprove of the proposal outnumber supporters by 48% to 44%. Its backers say that in the anonymity of the ballot box, people are more likely to vote yes.

In northern California, where much of the state’s marijuana is grown, drug enforcement agency busts and robberies are a threat to growers. Mexican cartels plant huge cannabis crops in remote forests protected by armed guards. It is a risky, violent business.

All that could change if the tide of legalisation continues to sweep across the US. A recent study estimated that a $50 an ounce tax would generate around $1bn a year for California, that the price of marijuana would drop by up to 80% and that consumption would rise as a result. That is a prospect anti-drug campaigners say is too scary to contemplate.