(Read NRO’s previous coverage of the Fast and Furious scandal — in which federal agents, acting on official orders, allegedly allowed Mexican cartels to purchase and traffic American guns — here.)

This morning, I was able to interview someone who is familiar with firearms-trafficking investigations on background. While we weren’t able to cover the details of Fast and Furious, the source did shed some light on the gun-trafficking problem and the strategies that law-enforcement agencies such as the Bureau of Alcohol, Tobacco, Firearms, and Explosives use to combat it.

The source emphasizes how difficult it is to arrest someone for “straw purchasing” — that is, buying a gun on behalf of someone who is not legally allowed to. “You pretty much have to prove that they falsified a statement on the firearms-transaction record,” the source says. On the form, gun buyers have to verify that the gun is either for personal use or a gift.

“You have to show, through tangible action, that that statement is false,” the person adds. “What you’re trying to do is prove somebody’s state of mind — that when they bought that gun, it was intended for someone else.” It is legal for a person to buy a gun, decide they made a mistake, and then quickly re-sell it.

In addition, the source says that regional cultures and state laws can make a difference. “Along the southwestern border, there’s a gun culture that exists where it’s not uncommon for people to own multiple weapons, to go into gun stores and buy multiple weapons, or buy and sell guns on a regular basis,” the source says. “What would be highly unusual in the northeast is commonplace in the southwest, so it’s harder to identify those trafficking firearms.”

Further, gun-trafficking techniques have grown more sophisticated of late. “Up until about five years ago . . . there was usually a direct connection between the actual straw purchaser and the person supplying money and receiving the gun,” the source says. “Then, cartels started to want and utilize more firearms, so they started using their narcotics-distribution rings to transport guns.”

This put many degrees of separation between the gun purchasers and the gangsters who wanted the weapons. “Instead of a direct transfer, it might take two, three, four months for guns to make their way out of the state — all the while not breaking any U.S. laws,” the source says.

Of course, this doesn’t answer the biggest questions: Are ATF whistleblowers telling the truth when they say that they let guns go even when they could have stopped them? Statements from ATF acting director Kenneth Melson seem to indicate they are. And if so, how were these guns — which were completely out of ATF surveillance as they slowly made their way to their intended recipients, and were recovered and traced only when they were discovered at crime scenes — supposed to lead law enforcement to the cartels?

“It’s very difficult to identify a straw purchaser, because you’re dealing with people without a criminal history, and who come from all walks of life,” the source says. “Unless you identify the person funding and orchestrating those purchases, you’re really not going to be able to have a significant impact on stemming the flow of firearms.”

One last Fast and Furious update: The Tampa Tribune ran an excellent article yesterday about Operation Castaway. Some have alleged that Operation Castaway allowed American guns to be trafficked to Honduras, just as Operation Fast and Furious is accused of letting guns “walk” to Mexico. The Tribune’s reporting casts doubt on this:

As with Operation Fast and Furious, the guns sold by Crumpler [the gun dealer who was targeted by Operation Castaway] wound up with least one killer, according to federal documents, as well as a drug organization in Puerto Rico, the hit man for a Colombian drug organization, a murder-for-hire gang and an effort to smuggle guns into Colombian prisons.

But unlike Operation Fast and Furious, these guns apparently wound up in the hands of criminals before Operation Castaway was launched, federal court records allege.

[Crumpler's attorney] said he did not think it was possible that guns from Operation Castaway wound up in the hands of criminals in Latin America once the investigation began because agents “closely monitored Crumpler’s activities after they got involved with him.”