They talk about explosive bullets and full-auto machine guns, implied to be US-origin, deployed by the Mexican narcos. Well, I'd like to have explosive bullets, too. Wish I can buy it from my neighborhood gunshop here in the states.
The Newsweek article mentioned, at the very end, that the narcos likely got the grenades and machine guns from Mexican military and police inventory, in addition to supplies from China, Europe, and Brazil. Well, great, then why are we talking about the US? And if the Mexican army is a prime weapon supplier of the narco-cartels, then it's intuitively obvious we should limit what we give to them, lest it ending up with the narcos.
Admittedly, the Mexican narcos are probably buying pistols through American dealers, in small quantities. Pistols have always been a prestige weapon worldwide, and their concealability make them both desirable and more smuggle-able. American truck screening on the border would help limit the flow. If Mexican smugglers can still get people and drugs into the US, though, we have little hope of stopping the flow of pistols into Mexico.
Therefore, a border fence is an eminently sensible idea in limiting the flow of weapons. If Mexico is serious about choking off the narco-cartels. That Calderone has not advocated a border fence shows that he cares more about sending people north than stopping drug violence.
PS: Edited for links and tags.