The executive actions on guns unveiled yesterday by President Obama drew predictable praise from gun control advocates and bile from gun-rights supporters and Republican lawmakers, including some who called his actions “unconstitutional.”

But, as some have noted, the actions themselves are extremely modest, raising questions about how much they will really do to stem gun violence.

Obama’s most significant step is an attempt to expand the number of gun sellers who conduct background checks on buyers. To do this, he is not changing the requirements for who is required to conduct a background check and who is not. Instead, he is giving a very high level of publicity to new “guidance” from the Bureau of Alcohol, Tobacco, Firearms and Explosives that simply explains what the current law is.

Under federal law, licensed firearm dealers have to comply with a set of regulations, including conducting background checks on prospective purchasers to make sure they are not prohibited from owning a gun because of a criminal record or other disqualifying factor. More occasional sellers of guns—one private individual selling to another private individual—do not have to follow these rules.

For decades, gun control advocates have decried this gaping loophole in the nation’s federal background check law. After a mass shooting at Sandy Hook Elementary School in December 2012, Congressional Democrats tried and failed to close this loophole by passing legislation to require background checks on more gun sales.

Obama is now approaching the problem from a different angle: He is focusing on gun sellers who may be operating in a gray area between being an occasional seller and a licensed dealer.

According to the ATF, its new guidance breaks down how federal courts have interpreted the somewhat fuzzy line between occasional gun sellers, who are not required to conduct background checks, and people who are “engaged in the business” of selling firearms, who must have a federal license, conduct background checks, and comply with other federal regulations on dealers.

A father selling off part of his personal collection of high-end firearms to finance his son’s college education does not need a federal firearms license, the ATF explained. But a man who lost his job and is now “buying firearms from friends and reselling them though an internet site” does need a license.

Experts say there’s some indication that gun sellers operating in this gray area are a problem, and that they play a role in supplying guns to people with criminal records.

Daniel Webster, the director of the Johns Hopkins Center for Gun Policy and Research, said sellers whose livelihoods don’t depend on gun sales may exercise prudence beyond what’s required by law when making transactions. When he conducted focus groups with gun owners in Texas, he said, many said they would not sell a gun without voluntarily checking whether a potential buyer had a state-issued permit to carry a concealed weapon, so they could be sure they were selling to a person who could legally own a gun.

But private sellers who are trying to make a profit may be less scrupulous about whether the person who is buying their gun could pass a background check, Webster said.

“If you are, on a regular basis, buying and selling a whole lot of guns and are doing that to make money, I think that probably clouds judgment,” he said.

Webster cited a November 2015 study by the gun control group Everytownfor Gun Safety, which analyzed a year’s worth of ads posted by unlicensed sellers on Armslist.com, an online gun marketplace. The report found that a small proportion of unlicensed sellers were selling a very large number of guns on the site: “Those offering 25 or more guns accounted for 1 in 500 sellers but offered 1 in 20 guns,” the report found. These private, high-volume sellers should be required to be licensed, the report concluded.

It’s not clear how the findings of this one study might reflect the larger online marketplace for guns—or the broader patterns of offline unlicensed sales.

“The bottom line: we don’t know how big this is, but we have enough evidence to know that thousands of guns are being sold by individuals who are selling a lot of guns in fairly risky kinds of ways,” Webster said.

The Everytown report also concluded that the vague legal definition of who should be a licensed gun seller had undermined efforts to prosecute people for dealing in firearms without a license.

Webster said it would be interesting to see if the White House’s attempt to clarify the law resulted in more cases targeting people for selling guns without a license. “Time will tell,” he said, noting that simply putting a spotlight on these sellers should also have “some deterrent effect.”

Even if the president succeeds in shrinking this gray area of the gun market, it’s not clear what effect that might have on gun violence overall.

Phil Cook, a Duke University gun policy expert, was one of the researchers who recently surveyed 99 inmates at the Cook County Jail in Chicago about how they obtained their guns. Very few of them described getting their guns from licensed gun dealers, or by stealing them.

For people with criminal records, “most of these transactions are not with people who are in the real business of selling guns, licensed or unlicensed. It’s much more casual transactions involving acquaintances, family members, street sources,” Cook said.

The White House emphasizedboth gun shows and Internet sales as places where it was easy to conduct risky sales with no background check requirements.

But Cook said that, according to surveys, neither the Internet nor gun shows were places where “the typical gang member or robber” goes to buy a gun.

“Nobody in the jail survey mentioned they had gone online,” Cook said. “I wonder if they would trust that arrangement. What they were telling us about the transactions they were involved with—on both sides, it was important that they either knew the other person or that they had somebody who would vouch for them. There was very little dealing going on among strangers.”

The 2015 Everytown study, which “analyzed every federal prosecution of ‘engaging in the business’ of dealing guns without a license in 2011 and 2012” also found “defendants relied on gun shows, online markets, or print ads to buy or sell their wares” in “approximately 10 percent of cases.”

At the same time, Cook said, that did not mean that gun shows and the Internet did not play a role in illegal trafficking. It’s extremely hard to track the movement of guns between their sale by a licensed dealer and the moment they are recovered at a crime scene or from someone not legally allowed to own them. Gun shows and the Internet might play a role in a chain of sales between these points, he said, and “might be supplying the pipeline of guns that are being trafficked into Chicago or New York.”

The ATF has no estimate for how many additional people, if any, may decide to get licensed and start conducting background checks as a result of its new guidance, though “it is reasonable to believe that there will be some increase in the number of new applications for firearms licenses,” ATF spokesman Corey Ray wrote in an e-mail.

Will the ATF start cracking down on gun sellers in the gray area that the guidance deals with? "Because this really isn’t new regulation, the requirements are already in place and enforcement is ongoing,” Ray wrote.