The Obama administration said new executive actions on gun control will withstand any legal challenge, a claim that might be put to the test by gun sellers, Second Amendment advocates or Republican lawmakers.

Legal experts say two areas are most ripe for challenges: Is the administration overstepping federal law as President Barack Obama seeks to expand which gun sellers must conduct background checks of buyers? And how will the administration handle a mental health component on background checks?

Republicans on Capitol Hill were quick to criticize the proposals, but some critics, including in the National Rifle Association, also hinted that the measures may not merit a challenge.

Obama said too many gun sales occur without background checks for buyers, particularly in private sales online and at gun shows. Gun control advocates have called on Congress to close that so-called loophole for years.

One potential lawsuit could challenge how much federal regulators widen the scope of enforcement actions against people “engaged in the business” of gun sales who do not get licensed or do background checks.

The question is how the new actions align with the current law that requires some gun sellers to be licensed and do background checks, legal experts said. The statute (PL 90-618) specifically excludes from the requirements people who make “occasional sales” or purchases for a personal collection or hobby.

“If they take enforcement actions contrary to that statute, that’s a problem,” said John Malcolm, a fellow at The Heritage Foundation and a former deputy assistant attorney general at the Justice Department from 2001 to 2004.

The Obama administration didn’t fully detail Tuesday how it would expand background checks for sellers. The White House said, however, that there is no specific threshold number of firearms that would trigger a seller to be licensed and to conduct background checks.

“But it is important to note that even a few transactions, when combined with other evidence, can be sufficient to establish that a person is ‘engaged in the business,’” the White House fact sheet said. “For example, courts have upheld convictions for dealing without a license when as few as two firearms were sold or when only one or two transactions took place, when other factors also were present.”

The “other evidence” and “other factors” are key for hobbyists or collectors, Malcolm said. A person might have sold only a few guns but advertise as a gun dealer, or sold only a few guns for such a huge profit that collecting or a hobby is not longer the principle objective of the seller.

Obama spoke Tuesday about Congress’ rejection of bills to expand background checks to sales at gun shows and online in 2013, when Obama and Democratic leaders, along with some Republicans, failed to pass gun law changes in the wake of the Sandy Hook Elementary School shooting where 20 children and six adults were killed in Newtown, Conn., in 2012.

Obama’s previous executive actions on guns did not expand background checks. This is “a step further,” the president said Tuesday.

Another potential legal challenge could come from a new Social Security Administration rulemaking process. The administration wants to include information in the background check system about Social Security beneficiaries who are prohibited from possessing a firearm for mental health reasons.

The Obama administration included that process on its list of Tuesday’s executive actions to reduce gun violence, as a way to help increase mental health treatment and to report to the background check system.

Depending on how those rules are written and what qualifies as a mental health problem, a military veteran with post-traumatic stress disorder or someone else with a mental health diagnosis could file a lawsuit if they lose their right to own a firearm, Malcolm said.

Even before Obama announced the details of his relatively modest changes, Republican lawmakers were sure he had overstepped his authority and subverted Congress’ will.

“This is a dangerous level of executive overreach, and the country will not stand for it,” House Speaker Paul D. Ryan said in a statement.

Republican lawmakers have repeatedly turned to the courts to rein in what they consider to be overreach by the Obama administration, although that looks less likely in this case.

A statement from House Judiciary Committee Chairman Robert W. Goodlatte, R-Va., said the proposal “does not go as far as originally reported” and mentioned the possibility of legislation — not litigation — as a response.

A Republican concern, expressed frequently throughout Obama’s presidency, has focused on the constitutional separation of powers.

House Republicans filed a lawsuit against the White House over the 2010 health care overhaul law (PL 111-148, PL 111-152) and the appropriations process.

The Supreme Court in 2013 ruled Obama overstepped his authority when he used recess appointments to fill the National Labor Relations Board.

Gun advocacy groups such as the National Rifle Association could add one more lawsuit to those it is fighting over gun control measures. But comments from the NRA Tuesday hinted that it might not be worth it.

“This is it, really?” Jennifer Baker, an official with the NRA’s Washington lobbying arm, was reported as saying in The New York Times. “This is what they’ve been hyping for how long now? This is the proposal they’ve spent seven years putting together? They’re not really doing anything.”

White House Press Secretary Josh Earnest, asked Monday about possible legal challenges, told reporters “a lot of the work that has gone on behind the scenes to take a look at what the president can do using his executive authority has been grounded in the knowledge that the gun lobby and the Republicans in Congress who regularly do their bidding are going to look for ways to try to stop it.”

“And we know that they are likely to try to pursue a creative legal theory to prevent the implementation of these rules,” Earnest said. “And that’s why the president wants to be sure that the recommendations that he receives and the executive actions that he carries out are going to stand up in a court of law.”