Current federal law prohibits gun ownership by felons, those who have been committed to mental institutions, minors, drug users and illegal immigrants. Someone in an ineligible category who goes to a gun store will be flagged in an instant background check and turned away.
But if you're one of the disqualified, take heart: You don't have to go to a licensed dealer. You might buy a firearm from your cousin, a woman you met shooting skeet or a guy with a table at a gun show.
If you're in a prohibited category, it's still forbidden for you to buy a weapon. But there's no background check. If you don't tell private sellers, they don't know. We have a system to block gun purchases by people deemed dangerous -- but we aid and abet cheating.
A major part of President Barack Obama's gun plan is to mandate background checks for all sales, including private ones. The only exceptions would be for "certain transfers between family members and temporary transfers for hunting and sporting purposes."
This remedy used to be about as controversial as the Fourth of July. In 1999, National Rifle Association Executive Vice President Wayne LaPierre endorsed "mandatory instant criminal background checks for every sale at every gun show. No loopholes anywhere for anyone." Sometime in the intervening years, though, he discovered that universal checks would merely help those "bent on destroying the Second Amendment."
But it's hard to think of a principled reason why the government should provide those barred from buying guns with a broad avenue for buying guns. It's like closing down police departments on Wednesdays and Fridays and expecting thugs to lay off as well. Either felons and other problematic individuals should be stopped from buying firearms or they shouldn't.
How much good would universal background checks do? Obama oversells them when he says this step is the "single most important thing we can do to prevent gun violence and mass shootings, like the one in Newtown."
The killer in that case got his guns by stealing them from his mother, who bought them from dealers. The alleged killer in Aurora, Colo., got his weapons at retail stores. Likewise, the man who killed six people at a Sikh temple outside Milwaukee.
Opponents say the change wouldn't help because criminals often buy their guns in illegal markets. In the case of a gang member who peddles stolen weapons to his colleagues, that's true. But expanding background checks would close off a major source of guns, making it harder for such criminals to find supplies.
Florida State University criminologist Gary Kleck, whose work is often cited by supporters of gun rights, told me, "My research found that state laws that provided background checks covering dealer sales showed some crime-reducing effects, so I reason that background checks that more comprehensively cover non-dealers as well as dealer transfers should do even better."
It wouldn't take much benefit to justify the trouble. Scholars Philip J. Cook of Duke University and Jens Ludwig of the University of Chicago say the change would be cost-effective if it reduced homicides by a mere 1 percent.
Nor would it violate the Second Amendment, any more than requiring demonstrators to get a parade permit offends the First Amendment. The inconvenience to law-abiding folks would be minimal, since buying or selling a gun is an infrequent event for the vast majority.
Some Republican senators oppose requiring private sellers to keep records, which are essential to making sure they actually conduct checks. Alarmists warn it would pave the way for gun registration, which would lead to mass confiscation.
This fear that an otherwise reasonable step will turn us into Nazi Germany is like thinking that if cops may search your home with a warrant, they will soon be sleeping in your guest room, showing up for meals and ordering pay-per-view.
Background checks have been going on since 1998, and amazingly, they haven't led to a national registry. Not every slope is a slippery one. Some are downright sticky.
Creating a hurdle for illegal buyers is no panacea. But it's a lot less crazy than leaving criminals on the honor system.