The US House of Representatives has voted to ease regulations that require extended background checks for gun buyers with mental health issues.
The checks, introduced under the Obama administration, are believed to affect an estimated 75,000 people.
The bill now needs to the approved by the Senate and signed into law by President Donald Trump.
The House also voted on Thursday on Obama-era rules and regulations on the environment.
The background-check rule was introduced to provide information on the gun-buying history of people receiving benefits for mental disability.
But Republican lawmakers argued that the regulation reinforced negative stereotypes that people with mental disorders are dangerous.
"There is no evidence suggesting that those receiving disability benefits from the Social Security Administration are a threat to public safety," said Congressman Bob Goodlatte.
"Once an unelected bureaucrat unfairly adds these folks to the federal background check system, they are no longer able to exercise their Second Amendment right," he added.
The House voted 235 to 180 in favour of abandoning the rule.
Barack Obama has previously told the BBC that the failure to tackle gun control had been the greatest frustration of his presidency.
Separately, the Senate gave final approval to a measure eliminating a rule that prevents coal mining debris from being dumped into streams. Mr Trump is expected to sign the move.
Republicans argued that the coal mining rule threatens thousands of jobs and that other industry regulations were already in place.
Senate Majority Leader Mitch McConnell described the law as "an attack against coal miners and their families".
The interior department said the rule, announced in the final days of Barack Obama's presidency in December, was aimed at protecting 6,000 miles (10,000km) of streams.
Democrats said Thursday's vote was an attack on clean water and a clear win for large coal mining companies.
Republicans are expected to take a series of actions in the coming weeks to reverse years of what they consider to be excessive regulation under Mr Obama.
Rules on fracking are also being scrutinised along with a number of other regulations introduced during Mr Obama's final months in office.