It comes via Representative Jennifer Wexton, the Democrat who recently replaced Barbara Comstock in Northern Virginia. The obvious inspiration is Andrew Ross Sorkin’s suggestion in the New York Times last year that financial institutions should reject or report gun purchases made on credit cards if they deem those purchases excessive, because some mass shootings have been committed with guns bought on credit.

The good news is that this is an actual bill in Congress, not liberals trying to enact gun controls through the financial industry that they couldn’t pass into law, the way Sorkin envisioned. The bad news is that, well, it’s still a terrible idea.

The bill is meant to get us to a place where the federal government’s Financial Crimes Enforcement Network and private institutions work together to monitor gun sales, with the latter reporting “suspicious” firearm-related activity to the former for investigation. The process starts with a “request for information” from financial companies regarding the data they already collect. If that data isn’t sufficient to monitor gun sales — and it isn’t — Congress will receive a report detailing “any barriers to obtaining the information.”

As Wexton’s own press release explains, “retail-level purchase information — or SKU-level data — has been hard to obtain and the effectiveness of the advisory [issued to institutions regarding what they’re supposed to report to the government] would depend on merchants sharing information about specific firearms products and accessories.” And as Sorkin himself put it, the way things currently work, “even the nature of the retailer [in a transaction] can be obscure” to credit-card companies because gun stores share a “Merchant Category Code” with general sporting-goods stores.

So, this puts us on the road to detailed, government-directed surveillance of gun purchases that goes far beyond the background-check system already in place. On top of that, the fundamental problem is that there’s no way to tell from financial data who’s buying a gun for legal purposes and who’s buying one to commit an atrocity.

America is home to plenty of gun enthusiasts who buy lots of guns and plenty of target shooters who buy lots of ammo. And as David French noted last year, it’s not at all uncommon for someone to go a long time without making any significant gun-related purchases but then spend a lot on a nice new weapon and accessories for it. In order to pick out the handful of domestic terrorists — who don’t always use very many guns or that much ammo — you’d also have to scoop up countless numbers of these innocent false positives.