I said that a check should be done. Currently the 4473 is the mechanism.
There is no reason use of 4473 couldn't be expanded to the unlicensed from what I can tell.
Regarding the response of "that won't stop a determined criminal.
1) Nothing will stop a determined criminal...
2) So, in lieu of that, we have a duty to make it harder.
3) It will stop a law abiding citizen from selling the gun to the gun when the 4473 comes back as negative... because they won't want to get hemmed up in the aftermath for selling to a known criminal. As it stands now, we don't know the guy's a criminal (except for those claiming clairvoyance and the ability to "sniff them out" based on their 5 minute chat with the potential buyer of course, we should definitely respect that claim)
4) It will force the criminal to be strictly black market.
5) When a criminal does killings with an illegal gun, it doesn't make the news.
6) When a criminal does the killings with a legally purchased gun despite him not being able to buy legally, it does make the news and doesn't help our cause.