There may good reasons for deploying the National Guard along the U.S.-Mexican border, but illegal firearms isn't one of them.

The administration recently launched a study to examine whether soldiers should patrol the Southern border to staunch the flow of firearms headed for drug dealers in Latin America. The silence you hear is the concern about armed drug gangs headed here. In short, the administration seems more concerned about the guns going south than the non-citizens streaming north.

"We're going to examine whether and if National Guard deployment would make sense," the president said. We look forward to seeing the study.

Stopping vicious Mexican drug gangs is surely a noble goal, as those gangs killed an estimated 6,000 people in Mexico last year. We also have a serious gang problem. The U.S. Department of Justice now estimates that 80 percent of U.S. crime is linked to gangs and drugs.

Yet, at least part of the president's plan is doomed to fail: Stopping Mexican gangs from getting guns will prove as difficult as stopping them from getting the drugs that they sell.

We are losing the drug war. Despite Mexico's strenuous efforts, our neighbor hasn't been able to stop the transnational flow of drugs through Mexico from other Latin American countries. Our own government hasn't done much better stopping contraband.

We won't do any better with guns. The drugs are extremely valuable and drug lords have many enemies, ranging from governments to rival gangs. So gangs have powerful incentives to own guns-to defend their lives and property-and access to vast smuggling networks.

Even digging a moat between the U.S. and Mexico wouldn't stop the flow of guns. Consider the experience of island nations -Ireland, Jamaica, and the United Kingdom- all of which saw murder rates climb after guns were banned. In the land of the disarmed, the one-gun man is king.

Certainly the Mexicans deserve our help when they investigate and prosecute gun murders in their country, just as we deserve their aid when we prosecute drug kingpins here. If we are going to talk about deploying armies on the border, shouldn't the administration ask the Mexicans to deploy their army to stem the tide of migrants headed here?