The Iron River may sound like something you'd find on a map of Westeros, but it's just a quaint term for the 200,000 guns manufactured or sold in the US moving across the border to Mexico every year.
The private-sale loophole that allows "collectors" in the US to sell guns without requiring identification, background checks, or paperwork — often to criminals and cartels at a tidy profit.
How "straw buyers" — that is, people with clean records — are paid by gun traffickers to pass background checks and buy firearms en masse without raising any red flags. If they are arrested in the act, however, their punishment rarely exceeds probation.
There are 130,000 licensed firearms dealers in the US from which ill-intentioned gun traffickers can make their shady purchases. If that doesn't sound like that many, consider that there are only 14,000 McDonald's restaurants.
Thanks to a Reagan-era law enacted ostensibly to protect the privacy of gun owners, the ATF finds its ability to efficiently trace guns hobbled because it can't use searchable, digital databases of sales.