(This story was updated at 1:55 p.m. ET.)
A visibly emotional President Barack Obama, at one point wiping tears from his cheek, unveiled his plan Tuesday to tighten control and enforcement of gun laws in the U.S., using his presidential powers in the absence of legal changes he implored Congress to pass.
Obama accused the gun lobby of taking Congress hostage, but said "they cannot hold America hostage." He insisted it was possible to uphold the Second Amendment while doing something to tackle the frequency of mass shootings in the U.S. that he said had become "the new normal."
"This is not a plot to take away everybody's guns," Obama said in a ceremony in the East Room. "You pass a background check, you purchase a firearm. The problem is some gun sellers have been operating under a different set of rules."
Obama wiped tears away as he recalled the 20 first-graders killed in 2012 at Sandy Hook Elementary School. He paid tribute to the parents, some of whom gathered for the ceremony, who he said had never imagined their child's life would be cut short by a bullet.
"Every time I think about those kids, it gets me mad," Obama said.
At the centerpiece of Obama's plan is a more sweeping definition of gun dealers that the administration hopes will expand the number of sales subject to background checks. Under current law, only federally licensed gun dealers must conduct background checks on buyers. But at gun shows, websites and flea markets, sellers often skirt that requirement by declining to register as licensed dealers.
Aiming to narrow that loophole, the Justice Department's Bureau of Alcohol, Tobacco, Firearms and Explosives is issuing updated guidance that says the government should deem anyone "in the business" of selling guns to be a dealer, regardless of where he or she sells the guns. To that end, the government will consider other factors, including how many guns a person sells, how frequently, and whether those guns are sold for a profit.
The White House also put sellers on notice that the administration planned to strengthen enforcement — including deploying 230 new examiners the FBI will hire to process background checks.
The impact of Obama's plan on gun violence remains a major question, and one not easily answered. Had the rules been in place in the past, the steps wouldn't likely have prevented any of the recent mass shootings that have garnered national attention. The Obama administration acknowledged it couldn't quantify how many gun sales would be newly subjected to background checks, nor how many currently unregistered gun sellers would have to obtain a license.
Pushing back on that critique, Obama said every time the issue is debated, gun rights groups argue the steps wouldn't necessarily have stopped the last massacre, "so why bother trying?"
"I reject that thinking," Obama said, arguing it would be worth it if the measures would prevent even a single gun death. "We maybe can't save everybody, but we could save some."
To lend a personal face to the issue, the White House assembled a cross-section of Americans whose lives were altered by the nation's most searing recent gun tragedies, including former Rep. Gabrielle Giffords and relatives of victims from Charleston, S.C., and Virginia Tech. Mark Barden, whose son was shot to death at Sandy Hook Elementary School in Newtown, Conn., introduced the president with a declaration that "we are better than this."
Invoking the words of Martin Luther King Jr., Obama said, "We need to feel the fierce urgency of now."
After the Sandy Hook shooting, Obama sought far-reaching, bipartisan legislation that went beyond background checks.
When the effort collapsed in the Senate, the White House said it was thoroughly researching the president's powers to identify every legal step he could take on his own. But a more recent spate of gun-related atrocities, including in San Bernardino, California, shootings have spurred the administration to give the issue another look, as Obama seeks to make good on a policy issue that he's elevated time and again but has failed until now to advance.
Attorney General Loretta Lynch and other top officials declined to explain why Obama hadn't taken these steps years ago and whether the administration had contemplated these actions in the past but determined Obama didn't have the authority.
"We're very comfortable that the president can legally take these actions now," said Lynch.
Obama plans to continue the weeklong push to promote the gun effort with a prime time, televised town hall discussion Thursday. The initiative also promised to be prominent in Obama's final State of the Union address next week.
Hillary Clinton, at a rally in Iowa, said she was proud of Obama's efforts, but warned that the next president could easily undo his changes.
"I won't wipe it away," Clinton said.
Republicans were quick to accuse Obama of gross overreach. Many of the Republican presidential candidates have vowed to rip up new Obama gun restrictions upon taking office, and some lawmakers are contemplating withholding Justice Department funds if it tries to implement them.
"I will work with my colleagues to respond appropriately to ensure the Constitution is respected," said Sen Bob Corker, R-Tenn.
The new guidance still exempts collectors and gun hobbyists, and the exact definition of who must register as a dealer and conduct background checks remains exceedingly vague. The administration did not issue a number for how many guns someone must sell to be considered a dealer, instead saying it planned to remind people that courts have deemed people to be dealers in some cases even if they only sell one or two guns.
The White House said it planned to ask Congress for $500 million to improve mental healthcare. Obama also issued a memorandum directing federal agencies to conduct or sponsor research into smart gun technology that reduces the risk of accidental gun discharges.