Editor's note: Gary Johnson is a candidate for the 2012 Republican presidential nomination and served as governor of New Mexico from 1994-2003.

(CNN) -- In 2002, I became aware of a woman who had already served more than six years of a 25-year prison sentence. Her crime? She was addicted to codeine, and she had fraudulently written herself more than 100 prescriptions for Tylenol III.

It seemed to me that this woman had already served far too much time in prison -- in fact, more than a person would likely serve if convicted of second-degree murder -- so I used my authority as governor of New Mexico to release her.

This sort of real-life example might have been difficult to envision 40 years ago, when President Richard Nixon publicly declared his intention to wage "a new, all-out offensive" against drugs. Back then, many Americans believed that tougher enforcement of drug laws would put an end to drug abuse in the United States once and for all.

But some, even within his own party, thought Nixon was going too far by involving the federal government in personal, private behavior. Raymond Shafer, for example, was the former Republican governor of Pennsylvania and Nixon's choice to lead his handpicked National Commission on Marijuana and Drug Abuse. Composed almost entirely of anti-drug conservatives, this commission was expected to issue a report supporting Nixon's new policies.

However, that isn't what happened. When the commission released its report in 1972, it recommended, in particular, against the criminalization of marijuana, arguing as follows: "The criminal law is too harsh a tool to apply to personal possession even in the effort to discourage use... the actual and potential harm of use of the drug is not great enough to justify intrusion of the law into private behavior, a step which our society takes only with the greatest reluctance."

This report received little media attention, and unfortunately, it had no impact on public policy. By the mid-1980s, virtually 100% of elected politicians from both parties supported the war on drugs in its entirety. Intellectual arguments against prohibition, however, did not die with the Shafer Commission.

William F. Buckley and Milton Friedman, two of the most respected conservative intellectuals of the late 20th century, were among the drug war's high-profile critics. These great thinkers did not argue that recreational drug use should be celebrated -- far from it! Instead, they argued that the prohibition of drugs was causing far greater harm to society than drug abuse itself. And they were right.

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When I ran for governor of New Mexico in 1994, I promised to bring a common-sense business approach to government. Everything was going to be a cost-benefit analysis -- how much of taxpayers' money are we spending, and what are we getting for the money we spend?

As governor, I was astonished to learn that half of what we were spending on law enforcement, courts and prisons was drug-related, and yet illegal drugs were cheaper, stronger and more available than ever. After further study, it became obvious to me that the drug war had created a lucrative black market and was enriching and empowering violent gangs and cartels. In many ways, it was like alcohol prohibition all over again, with similarly disastrous results.

I decided I simply couldn't allow the status quo to continue unchallenged, so in 1999 I became an advocate for legalizing marijuana and adopting harm reduction strategies for dealing with abuse of harder drugs (including prescriptions). I've been making these arguments ever since, and in recent months they have been resonating more strongly than ever.

The drug reform movement got a big boost last month when an international commission released a report criticizing the war on drugs. The Global Commission on Drug Policy was a 19-member commission that included Kofi Annan, a former U.N. secretary general; George Shultz, President Ronald Reagan's secretary of state; and Paul Volcker, a former chairman of the Federal Reserve.

Drug cartels, organized crime won the War on Drugs

The report's conclusions are clearly stated: "The global war on drugs has failed, with devastating consequences for individuals and societies around the world. Fifty years after the initiation of the U.N. Single Convention on Narcotic Drugs, and 40 years after President Nixon launched the U.S. government's war on drugs, fundamental reforms in national and global drug control policies are urgently needed."

Study these issues and I bet you'll agree that the Global Commission on Drug Policy is right. The Department of Justice reported that, in 2008, 2.3 million people were in our country's jails and prisons. Yet it is clearer than ever that the worldwide supply of drugs can never be wiped out -- no matter how strongly prohibitions are enforced.

If Republicans are truly serious when they talk about liberty and fiscal responsibility, and if they truly do their homework on the drug war, many will soon join me in my call for rational drug policy reform in the United States.

The opinions expressed in this commentary are solely those of Gary Johnson.