Despite its continuing prohibition, attitudes are changing. The 2007 National Drug Strategy Household Survey reported 70 per cent of respondents were in favour of legalising marijuana for medicinal purposes, while 75 per cent were in favour of further clinical trials. In 2013, the NSW Legislative Council’s inquiry into the use of cannabis for medical purposes concluded there was sufficiently robust evidence to support its use as a treatment option for certain conditions.

The rest of the world is changing faster though. Medical marijuana is already legal in Austria, Canada, Finland, Germany, Israel, Italy, the Netherlands, Portugal and Spain, and under state laws in more than 20 US states. In Colorado and Washington, recreational use is also legal.

The quest for additional taxation revenue is one of the reasons for this. Colorado expects to generate $US133 million ($144 million) in taxes annually.

Both medical and recreational sales are subject to a 2.9 per cent sales tax, while recreational sales are also subject to a 10 per cent sales tax and 15 per cent excise. The majority of the revenue is expected to come from recreational marijuana.

A right to effective medicines

There are many reasons why marijuana should be legal, especially for medical reasons. It is unconscionable to deny people an effective, safe solution for chronic pain, for example. There is no doubt it helps some conditions when nothing else works. It would also be cheaper than most current therapeutics.

The cultivation of cannabis on a commercial scale, along with the preparation and dispensing of medical marijuana, has the potential to generate significant employment. The largest cannabis dispensary in Oakland, California has over 104,000 customers and 120 staff.

Legal availability would deprive organised crime, including some bikie gangs, of a major source of income and relieve police of the cost of finding and destroying illicit crops. Of the $1.5 billion spent annually on drug law enforcement, 70 per cent is attributable to marijuana. State and federal budgets would benefit from reassigning police to catching criminals who harm and defraud other people, and many otherwise innocent people would be spared a conviction.

Legalisation of recreational use would also acknowledge the reality that most people have tried it, at some point, including me and US President Barack Obama. I do not recommend the use of marijuana except for medical purposes, but whether it is used for medical or recreational purposes should be for adults to decide for themselves. Whether others approve, or would choose it themselves, is not relevant. It is especially not the business of the government.

As the father of liberalism, John Stuart Mill, put it, “It is not legitimate, for government to involve itself in things that a person voluntarily does to him or herself, or that people choose to do to each other by mutual consent, when nobody else in harmed." Mill was not thinking of marijuana when he wrote that but he could have been.