One of the truisms endlessly repeated by anti-gun politicians is that the “lax” gun laws of rural, Republican-leaning states undermine the “tough” gun laws of Democrat-controlled large cities.

Sounds plausible enough until you actually check the figures. BATFE data studied by the Chicago Police Department showed that 28 percent of guns used in local crimes were bought in nearby suburbs, with 43 percent being bought in Illinois.

Illinois requires a Firearms Owners Identification card to purchase, or even handle, a firearm at a dealer or gun show. Even private sellers are not allowed to sell a gun without inspecting the buyer’s FOID card.

Indiana, which has very gun-friendly policies on concealed carry and Title II firearms, and borders Chicago on the south, was the source for only 18 percent of the guns traced, while Wisconsin, the second-closest state, accounted for just 4 percent.

It is a local tradition in Chicago to blame just about anything on downstaters who live much closer to Arkansas or Kentucky than to the Windy City. But in this case, the Chicago suburbs, many of which are closely aligned politically with the city, are the source of almost a third of Chicago’s crime guns.