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WASHINGTON — The Republican-led Senate voted Wednesday to block an Obama-era regulation that would prevent an estimated 75,000 people with mental disorders from being able to purchase a firearm. The measure now goes to President Donald Trump, who is expected to sign it.

The regulation was crafted as part of President Barack Obama's efforts to strengthen the federal background check system in the wake of the 2012 massacre of 20 young students and six staff at Sandy Hook Elementary School in Newtown, Connecticut. Adam Lanza, a 20-year-old man with a variety of impairments, including Asperger's syndrome and obsessive-compulsive disorder, shot and killed his mother at their home, then went to school where he killed the students, adults and himself.

The Obama administration rule required the Social Security Administration to send in the names of beneficiaries with mental impairments who also have a third party manage their benefits.

But lawmakers, with the backing of the National Rifle Association and advocacy groups for the disabled, opposed the regulation and encouraged Congress to undertake a rarely successful process designed to void regulations that Congress takes issue with.

The 57-43 vote to revoke the regulation sends the measure to Trump.

With a Republican ally in the White House, the GOP has moved aggressively on several fronts to rescind some of the Obama administration's final regulations on the environment, financial reporting and now guns. Under an expedited process established through the Congressional Review Act, a regulation is made invalid when a simple majority of both chambers pass a joint resolution of disapproval and the president signs it.

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A Bushmaster rifle lies on the ground at Sandy Hook Elementary School following the Dec. 14, 2012 shooting rampage in this evidence photo released by the Connecticut State Police. Connecticut State Police via Getty Images

Sen. Charles Grassley, R-Iowa, spearheaded the repeal effort and said the regulation unfairly stigmatizes the disabled and infringes on their constitutional right to bear arms. He said that the mental disorders covered through the regulation are filled with "vague characteristics that do not fit into the federal mentally defective standard" prohibiting someone from buying or owning a gun.

Grassley cited eating and sleep disorders as examples of illnesses that could allow a beneficiary to be reported to the background check system if they also have a third party to manage their benefits.

"If a specific individual is likely to be violent due to the nature of their mental illness, then the government should have to prove it," Grassley said.

Related: Gun Sales Might Slump Under Trump — But He Could Fire up the Industry

The rule isn't scheduled to go into effect until December. It only would apply to those receiving disability benefits. However, someone who is added to the background check system before retirement age would remain there after retirement age.

Sen. Chris Murphy, D-Conn., said he didn't know how he could explain to his constituents that Congress was making it easier rather than harder for people with serious mental illness to have a gun.

"If you can't manage your own financial affairs, how can we expect that you're going to be a responsible steward of a dangerous, lethal firearm," Murphy said.

Sen. Ron Wyden, D-Ore., argued that anyone who thinks they're treated unfairly can appeal, and are likely to win if they're not a danger to themselves or others. But Grassley said federal law requires a formal hearing and judgment before depriving someone of owning a firearm due to mental illness.

Gun rights groups weren't the only organizations upset about the Obama administration's regulation. The American Civil Liberties Union criticized it, too. The ACLU said the rule advanced a harmful stereotype that people with mental disabilities, "a vast and diverse group of citizens, are violent." More than a dozen advocacy groups for the disabled also opposed the Obama administration's regulation.

The NAACP, the United States Conference of Mayors and the National League of Cities supported the Social Security Administration's efforts.

"This heartless resolution puts the most vulnerable Americans at risk," said Dan Gross, president of the Brady Campaign to Prevent Gun Violence. "Make no mistake, this vote was really about deepening the gun industry's customer pool, at the expense of those in danger of hurting themselves or others."

Meanwhile, the GOP-led House will seek to rescind more Obama-era regulations later Wednesday, including a Labor Department rule that critics say unduly restricts efforts in some states to test unemployment insurance applicants for drug use.