Some researchers have found their work limited too, according to Glen Pierce, a gun policy expert at Northeastern University. Pierce says that before Tiahrt, he could access ATF data, down to the dealer level, to be used to understand just how the gun trade works. Now, he says, the big data sets are hard to get.

“You have to get the approval of police agencies or possible entire states to do research with their trace data,” Pierce said. “So if you want to do national studies and you want to look at effects of laws in one state across other states, it becomes very hard to do this in a comprehensive manner because you need to get approval from all these jurisdictions, which is cost-prohibitive. So it effectively prevents that type of research from being conducted.”