JUDY WOODRUFF: Now Ray Suarez takes a closer look at the potential powers and limitations on what the president and individual states can do.
RAY SUAREZ: And for that, we get two views from people who have written extensively on gun-related issues.
Adam Winkler is a professor of constitutional law at UCLA School of Law and author of "Gunfight: The Battle Over the Right to Bear Arms in America."
And John Lott has been a prominent voice in the gun rights debate, arguing against further restrictions. He's an economist and the author of "More Guns, Less Crime."
And, John Lott, just heard the president and Pat Quinn, the governor of a very large state, talking about using state and federal power to work against gun violence. Is there any track record?
Have there been laws passed either at the state or federal level that showed any track record in pushing down the amount of violence, the number of incidents, restrictions on size, type, availability of weapons, anything we can point to in the past?
JOHN LOTT, author, "More Guns, Less Crime": Right.
Well, obviously, I understand the reactions. I mean, we have all been torn apart by this. I wish the problems were quite as simple as the president and the governor seem to indicate.
We have tried a lot of the laws. The governor himself was saying he'd like to see something similar to the assault weapons ban that we had before.
If you go back when the assault weapons ban sunset in 2004, many of the same people who are pushing it now, Sen. Dianne Feinstein, Sen. Chuck Schumer, were predicting large increases in murder rates and violent crimes when it sunset. Since it sunset, though, murder rates and violent crimes have both fallen by about 20 percent.
Somebody should ask them why they were so far off in terms of their predictions. And, you know, the other -- and that covered many of the things that are being talked about now, from limiting the size of ammunition clips, to bans on so-called assault weapons.
I think a lot of the problem is, with all due respect to the governor, I'm not sure he really understands what the different types of guns are. There's something that's put out there, this mythical assault weapon. It's really trying to ban guns on the way they look on the outside, rather than how they actually function.
RAY SUAREZ: Let me turn to Prof. Winkler at this point.
Is there any track record, sir, for using state or federal regulation to turn back the rate, the frequency of gun violence?
And respond to John Lott's point about previous legislation not having done much.
ADAM WINKLER, UCLA School of Law: Well, it's true that a restriction on assault weapons is not likely to have a huge impact on ordinary crime rates, in part because assault weapons are generally not the preferred firearm of the criminal, who generally prefers to have handguns at their disposal.
Since 2004 and the sunset of the assault weapons ban, we have really seen a spike in the number of incidents of mass shootings. So maybe these firearms are attractive to them.
We have also seen, with the Brady background check bill, adopted in 1993, that requires background checks, that about 60 percent of gun purchases, that well over 1.5 million people who have tried to buy firearms from federal licensed dealers have been turned away for failing that background check.
I think there is strong evidence that if we require a background check on every gun purchase, we will close a major loophole that allows criminals or the mentally ill to get their hands on gun easily.
RAY SUAREZ: John Lott, that is often referred to as the gun show loophole, a place where in fact you don't have to have your past looked over. And that's been talked about quite a lot in the past several days, closing that, just as a starting point for the national response to what happened Friday.
JOHN LOTT: Right.
I have to disagree with what Adam just said. If you look at the Brady Act, which is obviously a part of this puzzle here in terms of background checks, when he cites the 1.9 million number, that's initial denials.
Something like 90 -- I can't remember the exact number, but it's like 98 percent or so of those are false positive.
And so what happens? You have a name that is similar to somebody else's name, and they will flag you, and you will be initially denied.
RAY SUAREZ: So, sir, are you saying a lot of those people come back and eventually do get guns?
JOHN LOTT: I'm saying criminals aren't trying to buy guns that way.
Those -- pointing to the number of initial denials, rather than final denials, is not a very useful way of looking at it.
And, in addition, with regard to the so-called gun show loophole, it's really a bit of a misnomer.
What they -- what wants to be done is to have -- regulate and have background checks on all private transfers. So if you're a father giving a gun to a son or whoever, you would have to go through a background check system.
The notion that they focus on gun shows, I mean, I could go outside the gun show and transfer the gun there.
Are they going to say that that's OK then? When states have passed these rules, usually, it's going to be on all private transfers. And that's fine, if they want to make that argument. But the thing is, again, both criminologists and economists have looked at this extensively.
And I don't know of any study by either economists or criminologists that have found a benefit from having the states that have these types of background checks. There's only about 0.7 percent of all crime guns come from either gun shows or flea markets.
RAY SUAREZ: Prof. Winkler ...
JOHN LOTT: And so ...
RAY SUAREZ: Let's give him a chance to respond.
JOHN LOTT: Sure. Sorry.
ADAM WINKLER: Well, the truth is, we don't really know, because not all the gun shows -- you don't have to report the sales at gun shows.
And it also defies logic to think that gun shows are not a vehicle for criminals to get their hands on guns.
If you're a criminal, one of your big -- the big issues you face is that you can't go to a gun store and buy a gun because they will do a background check on you.You could buy a gun in the black market. And many criminals indeed get their guns just through the black market.
But if you want to have selection and want to have the kinds of choices that you get at a gun store, you go to a gun show.
I agree with John that it's not a gun show loophole. Gun sales at gun shows occur with the exact same rules as gun sales everywhere else. The problem is that they are basically a marketplace for people who don't want to do a background check to go and purchase a firearm without having to undertake one.
It's time that we require every single person who buys a gun to go through a background check. That doesn't offend anyone's Second Amendment rights.
And all over the country, when I went and talked about guns to people when I was out there on a book tour for "Gunfight," I found gun owners all over telling me they wanted to do more to see that criminals and the mentally ill don't have easy access to guns.
Make it difficult for criminals to get their guns.
RAY SUAREZ: Professor Lott, quick response?
JOHN LOTT: Yes, sure.
Well, there's costs and benefits from all these laws. For example, during the Clinton administration, the gun show -- or the computer checks were shut down for about six days or so each month. And they run into problems now.
So, if you're running a gun show, and let's say it's shut down for an hour or two hours or a day or a weekend, all your sales are gone.
Imagine running a grocery store where, randomly, the government would shut you down and not tell you when you would be able to go and get back up. That is a real cost.
Now, if the government wants to go and guarantee that that won't be or compensate people financially for that, my guess is the amount of opposition would quickly be reduced.
If they think that there's this big gain in terms of reduced crime, despite the fact that there's no academic studies there, then share part of that gain to offset the costs that would be imposed on those individuals that would have their businesses possibly ruined otherwise.
RAY SUAREZ: Gentlemen, it's apparent there's a lot more to talk about on this issue. We will continue this conversation.
Thanks for joining us.
JOHN LOTT: Thank you.
ADAM WINKLER: Thank you.
GWEN IFILL: And you can watch the president's entire news conference on gun policy initiatives on our website.