As Assistant Homeland Security secretary,  Alan Bersin has been dubbed the “Border Czar” for the administration of President Barack Obama. He was back in his old neighborhood last week to visit the U.S.-Mexico border in California and address an audience at the Institute of the Americas at UC San Diego. His previous role there was United States attorney and he played a big role in increasing border security in the 1990s by helping to implement “Operation Gatekeeper” along the U.S.-Mexico border.

Before his speech, which covered everything from immigration to the drug war to the safety of U.S. travelers in Mexico, Bersin took a moment to draw attention to the issue of vehicle inspections at the border and the good they’ve done in the war on drugs. According to Bersin, stepped-up inspections of vehicles heading to Mexico from the United States have yielded more than $40 million in seizures of bulk cash since April.

That’s a serious blow to the drug cartels, which are forced to watch every million now that Mexican President Felipe Calderon has made it his mission to run them out of business. With fewer drugs coming north, and more drug dealing in Mexico at smaller profits, the drug syndicates are feeling the heat. They move drugs into the United States, but they also move truckloads of guns and cash into Mexico from the United States. U.S. attorneys have to crack down on all three commodities.

Experts on the drug war say that, while the cartels hate losing drug shipments or stashes of armaments, they really hate it when they lose bundles of cash because that’s the walking-around money they need to do business. So these cash seizures are a hugely important weapon in the battle against drug traffickers, a battle in which the United States is a full partner.

Homeland Security Secretary Janet Napolitano ordered the vehicle searches along the entire U.S.-Mexico border to crack down on guns and cash headed south.

At the time, there was concern that these procedures would infringe on individual liberty and inconvenience people on both sides of the border to the point of discouraging the cross-border commerce on which this region depends so heavily. Those concerns are legitimate and not to be taken lightly, especially during a recession when, in fact, we need to do everything we can to encourage more cross-border business.

But there is a greater good to be served. According to border law enforcement officials, violence related to the Mexican cartels is declining as the pressure on all fronts increases. They can get plenty of drugs, but intercepting their cash can shut them down.