Visiting Mexico last week, President Obama said he will fight drug violence: "I will not pretend that this is Mexico's responsibility alone. The demand for these drugs inside the United States is keeping these cartels in business" (http://tinyurl.com/d4kjto).

I don't expect politicians to be sticklers for logic, but this is ridiculous. Americans also have a hefty demand for Mexican beer, but there are no "Mexican beer cartels." When Obama visits France, he doesn't consult with politicians about "wine violence." What's happening on the Mexican border is prohibition-caused violence.

A legal product is produced and traded openly, and is therefore subject to competition and civilizing custom. If two beer distributors have a disagreement or if a liquor retailer fails to pay his wholesaler, the wronged parties can go to court. There's no need to take matters violently into their own hands. As a result, in legal industries the ability to commit mayhem is not a valued skill.

On the other hand, dealers in a prohibited product operate in the black market. Upstanding businesspeople stay away, relinquishing the trade to those without moral scruples. Black-market operators can't resolve disputes in court, so being good at using force provides a competitive advantage.

Politicians gave us prohibition and created the conditions in which violence pays. This doesn't excuse those who commit it, but the fact remains that a legal drug market would be as peaceful as the beer, wine and whiskey markets. When alcohol prohibition, which spawned large-scale organized crime, ended in 1933, there was a brief upsurge in drinking, but America became a more peaceful and less corrupt place.

We should learn from that, but we haven't. American politicians are largely responsible for the atrocities now taking place.

That's not what they want to hear, of course, so they blame others. Their "solution" to increasing violence is to crack down even more on production and distribution of some drugs. This has never worked before, and it won't work now. Black-market profits are abnormally high because of the risk premiums and limited competition, so plenty of people will want to enter the business. Wipe out one cartel, and another is waiting to take its place. The high profit margins leave plenty of cash to bribe judges, cops and border guards. Even in America.

When American politicians scapegoat drug consumers, they bring the court system to a standstill and clog prisons with nonviolent offenders who are stigmatized for life. Minorities bear the brunt of any crackdown.

When will we learn that prohibition doesn't banish a popular product? It merely turns the trade over to thugs. The result is worse for society than if drugs were legal. After decades of the "war on drugs," anyone can still buy most any drug he wishes. Authorities can't even keep drugs out of prisons.

Another aspect of this issue has been overlooked, especially by conservative supporters of the drug war: President Obama and Secretary of State Clinton have promised the Mexican government they will stop the southern flow of American guns said to be used by the drug cartels. A war on drugs inevitably becomes a war on guns. Yet conservative Second Amendment advocates refuse to see the connection.

Obama's drug warriors are happy to link the issues. The president says, "More than 90 percent of the guns recovered in Mexico come from the United States, many from gun shops that line our shared border, and that's why we're ramping up the number of law enforcement personnel on our border" (http://tinyurl.com/dk7hh3).

That 90 percent figure has been repeated many times, but FactCheck.org says it's bogus:

"The figure represents only the percentage of crime guns that have been submitted by Mexican officials and traced by U.S. officials. ... U.S. and Mexican officials both say that Mexico recovers more guns than it submits for tracing ... " (http://tinyurl.com/c6zbcz).

And FactCheck says Mexico only submits those it already has reason to believe came from the United States.

Once again the politicians show contempt for the truth as well as for freedom.

John Stossel is co-anchor of ABC News' "20/20" and the author of "Myth, Lies, and Downright Stupidity." To find out more about John Stossel and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate Web page at www.creators.com.