US States legalise Dagga
This month, two US states, Colorado and Washington, voted to legalise, regulate and tax dagga.
Dagga is the most widely used illicit drug in the US. Legalisation advocates say the recent votes mark the beginning of the end of the drug's prohibition. But authorities are wary. "The Colorado chiefs of police are incredibly concerned with regard to public safety as a whole," says Chief John Jackson of the Greenwood Village police department, and legislative chair of the Colorado Association of Chief of Police.

The laws forbid under-21s from possession dagga, and Washington bars dagga adverts from within 305m of schools, playgrounds, parks and other places children gather.

"Whether it's socks or weed the first thing you have to do is look at who's your target," says Rahul Panchal, an advertising creative director in New York. Panchal says the core market is well established: "Mid-twenties stoner guys". Those people are already comfortable smoking dagga and are happy to buy it with minimal packaging or advertising effort.

Entrepreneurs in search of big profits should look at the dairy industry, says Panchal.

"The lowest margin is to just sell milk," he says, while the real money is in processed products like cheese and yogurt. "I would sell pot products: cookies, brownies and such. That's where the money's going to be."

The Washington law sets a threshold of five nanogrammes of THC, the active ingredient in dagga, per litre of blood, and Colorado's legislature is expected to enact a similar threshold.

Sheriff Ozzie Knezovich of Spokane County, Washington says officers who suspect a driver has smoked too much will have to summon a paramedic to draw blood for a test. "How much of an added expense is that going to be to our agencies?" he asks.

Americans have stubbornly resisted millions of dollars spent on anti-drug education. Despite decades of law enforcement efforts, dagga remains widely available just about everywhere.

In 2002, 6.2% of Americans over the age of 11 reported using dagga within the past month, according to a Substance Abuse and Mental Health Services Administration study. By 2011 that figure had risen to 7%.