Grassley claimed the regulation unfairly stigmatizes people with disabilities and noted it was opposed by more than 20 disability and civil rights groups.
But Senate Minority Leader Charles Schumer, D-N.Y., said it was outrageous that with national security the top issue, "the GOP would pass a bill to weaken the FBI's firearms and explosives background-check system".
A controversial gun control regulation, finalized in the final weeks of the Obama administration, appears to be reaching the end of its very short lifespan.
It was implemented by former President Obama after the 2012 Sandy Hook shooting, which saw 20 students and six teachers killed at an elementary school by 20-year-old Adam Lanza.
The House voted to block the rule earlier in February, meaning the measure now heads to President Donald Trump's desk.
"Under the regulation, the agency is not required to adequately prove that individuals meet the established legal definition of "mental defective" or even provide due process before revoking their Second Amendment rights", Grassley said.
The rule isn't scheduled to go into effect until December. However, someone who is added to the background check system before retirement age would remain there after retirement age.
"If you can't manage your own financial affairs, how can we expect that you're going to be a responsible steward of a risky, lethal firearm", he said. "There is no evidence to support that general idea, and consequently, people being denied constitutional rights without due process", says Grassley.
The law stopped people who receive disability benefits from buying guns, affecting an estimated 75,000 people.
"The regulation at issue here was issued by the Social Security Administration under President Obama".
The NAACP, the United States Conference of Mayors and the National League of Cities supported the Social Security Administration's efforts. "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".