One important question is whether laws criminalizing marijuana have effectively reduced supply and use. It would appear from available data that they have not. Despite billions spent on anti-cannabis law enforcement and a 30% increase in the number of arrests in California since 2005, marijuana remains the most frequently used illegal drug. Nationally, an estimated $10 billion is spent each year enforcing marijuana laws, yet an ongoing study funded by the National Institute on Drug Abuse has concluded that over the last 30 years, the drug has remained “almost universally available to American 12th-graders,” with 80% to 90% saying the drug is “very easy” or “fairly easy” to obtain.

On the health side of the equation, scientific consensus is that while cannabis may pose some health risks, they are less serious than those posed by alcohol and tobacco. The approach taken to regulating these other harmful substances, however, hasn’t been to criminalize them but to regulate their distribution, to impose taxes on their purchase and to educate the public about their risks. These measures have been shown to be effective, as in the case of cigarette consumption, which has dropped dramatically.

On the other hand, cannabis prohibition has not achieved its stated objectives. As detailed in a report published last week by my organization, the International Centre for Science in Drug Policy, research funded by the U.S. government clearly demonstrates that even as federal funding for anti-drug efforts has increased by more than an inflation-adjusted 600% over the last several decades, marijuana’s potency has increased by 145% since 1990, and its price has declined 58%.