As a company that specializes in pre-employment screening, including background checks, our clients occasionally ask our opinion on background checks for guns. As a follow-up to my earlier article on Dylann Roof, I did some digging into the rules for gun purchases, overall. I was surprised by what I found—and I think you’ll agree.

In addition to furor over mistakes made by agencies like the FBI, there is some concern about the “instant” background checks that most firearm sellers use. They only take a few seconds—certainly longer than a properly conducted pre-employment background check.

However, an even greater concern may be the manner in which private gun sales are handled. A recent study by researchers at Northeastern University and Harvard University found that over the past two years, one in five U.S. gun owners had obtained a firearm without a background check. The study also found that the share of gun owners who acquired firearms via private sale without background checks was significantly larger (57 percent) in states without laws regulating such purchases than in states with legislative regulations (26 percent). Among all 50 states, the study noted, “30 states don’t require background checks on private firearm sales.”

In the study, “private gun sales” are defined as the “millions of gun transfers annually that pass from one private owner to another without a formal vetting process and so without knowing whether the recipient is someone society deems a lawful possessor of firearms.” If I read the study correctly, it appears that in many states, someone could purchase a firearm from a licensed dealer and pass a background check—and then sell or give it to anyone else without another check being required.

I don’t see how that type of sale could be regulated or prevented in a meaningful way unless the laws are changed. That made me wonder, what happens if a gun sold privately is used in a crime? Is the person who purchased it, passed the background check, and then sold or gave it away held responsible? Are gun crimes more common in states that allow private sales without background checks? Has anyone done a study to see how many crimes are committed by private gun purchasers with no background checks?

Numerous studies show there is a correlation between the decline in gun violence and the requirement for gun dealer point-of-sale background checks. Recently, gun violence is on the upswing, although it remains far lower than it was in the early 1990s (total gun homicides dropped by nearly 50% between 1993 and 2013). Where it goes from here is anyone’s guess.

Is it time for regulations regarding private gun sales? Or, would that practice be too intrusive or difficult to monitor? I’ll be watching closely to see how the situation pans out under the new administration.