To the many delights of Mexico's U.S. bordertowns — food, curios, pharmaceuticals, music, tequila and whatever goes on in their zonas de tolerancia — add a new attraction: drugs.

Once as illegal in our neighbor nation as they are here, give or take a couple of exceptions, drugs in small amounts last month were decriminalized.

We're not just talking marijuana; cocaine, heroin, LSD, methamphetamine — in small amounts, possession won't land you in the cárcel. Theoretically you could find yourself being lectured about drugs' dangers — and there are plenty of them — while on your third bust, treatment would be mandatory. But no more than four joints of grass? Less than half a gram — four lines — of cocaine? Fifty milligrams of heroin, or 40 of meth? Ándele ...

The Felipe Calderón administration figures the new law is at least a start in its struggle with corruption: Crooked cops suddenly have no statutory basis for shaking down small-time users through threats of serious sentences.

But what will this do to the U.S. "war on drugs?" Well, it further exposes our tragicomic cops-and-robbers policy, which has made so many narcotraficantes rich by charging what the illicit market will bear, as the nonsense that it is.

We're especially intrigued by the treatment side of the new law, since that, along with preventative education, is crucial to reducing drug use to a low roar. Applying that provision in Ciudad Juárez to day-tripping college kids from Las Cruces might be tricky, unless junior has a panic attack and seeks help himself.

Then there's the kid's condition when he comes back across the bridge and hops in the car. On certain of those decriminalized potions, he's a real menace to public safety — which he always has been when overdoing it in a cantina. But borderland police have long known that drunkenness is only one kind of impairment to deal with on desert roads, even though drugs have slipped below the radar in New Mexico's neo-prohibitionist rush. Unless the new crowds of doper-tourists designate a driver, there's trouble to anticipate.

As for our customs officials, will this mean strip-searching every sloe-eyed lout who enters the U.S.? Maybe — at least until this country wakes up and issues similar decriminalization laws.

Lest the preaching bloc raise alarms about lemming-like flows of norteamericanos into the nearest Mexico port of entry, our nation's morals will be aided by a remnant of Bush-era fortress-building: It now takes a passport, a newfangled "passport card" or an "enhanced driver's license" to sally back across the international line. The thought of lining up to apply for such documentation might keep dedicated dopers buying from their usual sources, for now, anyway.

Unless our little darlings start dying in droves during over-the-border overdoses, this experiment might lead to a long-overdue effort to take the narcotics trade away from the increasingly brutal Mexican and Colombian cartels. Already we can envision those highly organized criminals thinking up ways to sabotage their government's fresh approach to a rancid problem.

Diplomatic pressures might yet be brought to bear on the Calderón administration's new foray on the dope front. But it deserves the attention of our country's long-frustrated drug-policy people.