What would legalizing marijuana in California, America’s most populous state, mean to the drug cartels whose fight for access to American markets have turned parts of Mexico into war zones? Shrinking profits? Certainly. Less violence? Maybe.

These topics are being raised as the U.S. heads towards Nov. 2 mid-term elections which in California include a ballot initiative, Proposition 19, providing for marijuana to be treated like alcohol and tobacco for Californians over 21. A vote in favour would end 73 years of prohibition and have enormous political impact not only on the rest of America but also on the long-running global war on drugs.

Experts on the issue have been working overtime and the latest of a string of academic studies, out this week, came from the RAND Corporation, a California-based think tank. The voluminous paper is entitled: Reducing Drug Trafficking and Violence in Mexico – Would Legalizing Marijuana in California Help? The study’s four authors, all prominent authorities on the illegal drug business, hedged their answer.

“Our best guess,” they concluded, “is that legalizing marijuana production in California would wipe out essentially all DTO (Drug Trafficking Organization) marijuana revenues from selling Mexican marijuana to California users; however, the share of Mexican marijuana in the United States that comes from Mexico to California is no more than one-seventh of all Mexican imports.”

Note the word “guess.” It stems from the fact that most figures in the long debate on the war on drugs are estimates and many have been manipulated for ideological purposes. According to the researchers, the drug cartels’ marijuana business in the entire United States could virtually evaporate if high-quality marijuana from California were diverted from legal production and smuggled to the rest of the country.

And what effect would that have on the Mexican drug wars, in which the death toll is nearing 30,000? Again, a scholarly hedge, given the difficulties in measuring the drug market and its suppliers. Thus: “It is unclear whether reductions in Mexican DTOs’ revenues would lead to corresponding decrease in violence…The effect of reducing DTO marijuana revenues on violence is a matter of conjecture…(and) could well change over time.”

The reason for the academic caution is simple: there’s no historic precedent for what might happen in California – one state making legal a substance that remains illegal elsewhere in the country and the rest of the world. It is not as straightforward as the 1933 repeal of alcohol prohibition which applied to the entire country.

CURRENT OF OPINION

The before-and-after sequence of lifting prohibition is so obvious that the U.S. Congress passed a resolution on the 75th anniversary of the repeal noting that it had replaced a “dramatic increase” in organized crime with “a transparent and accountable system of distribution and sales” that generated billions of dollars in tax revenues and boosted the sick economy.

While much of the debate on the pros and cons of Proposition 19 has centered on economics, there is an international policy dimension that weighs heavily in Mexico. As former Mexican foreign minister Jorge Castaneda recently put it – how can you have Mexicans kill each other over trafficking a drug that is freely available on the other side of the border? If that happened, it would be logical for Mexico to legalize as well.

Would that end Mexico’s violence? “No. But the minute we start removing some of the money the cartels make, then they have less funds available to buy guns, to buy people, to recruit people, to do all sorts of things.” Castaneda was talking about marijuana. Former President Vicente Fox last August went a step further and proposed legalizing all drugs “to break the economic structure” of the drug cartels.

Fox’s successor, Felipe Calderon, who launched the war on drugs, deploying the military, shortly after he was elected in 2006, is opposed to California’s legalization proposition and has publicly complained about “a current of opinion” portraying marijuana as a drug that is not harmful. In his eyes, that’s wrong and prohibition should therefore stand.

That puts Calderon at odds with another of his predecessors, Ernesto Zedillo, and two more former Latin American presidents from countries that suffered from drug violence, Fernando Henrique Cardoso of Brazil and Cesar Gaviria of Colombia. In 2009, they chaired a blue-ribbon panel that rated the international drug war a failure and urged governments to look into “decriminalizing” marijuana, the world’s most widely used illicit drug.

This has been a growing trend for several years as attitudes towards marijuana softened – and more people around the world used it. (According to the U.N.’s 2010 World Drug report, up to 191 million people used marijuana at least once in 2008). Countries that have formally decriminalized the herb’s use include Argentina, Colombia, Luxembourg, Portugal, Spain, the Netherlands and Italy.

No country, or jurisdiction, has gone as far as Proposition 19 would take California. Its passage, in a state with 37 million people, would probably prompt a host of legal challenges. It would also send a message to government drug warriors the world over – you’ve been tilting at windmills. It’s time to stop.