WASHINGTON (AP) — Republicans faced a major hurdle in their attempt to ease restrictions on gun silencers and firearms with short barrels, as the Senate parliamentarian indicated that this measure would have to gain 60 votes to be part of their significant tax and immigration legislation.

Gun rights advocates had been vigorously pushing for this change, aiming to classify silencers and short-barreled guns similarly to long guns. Meanwhile, gun-control supporters welcomed the parliamentarian’s decision, emphasizing that these items have been subject to regulation for almost a century due to the risks they pose to first responders and public safety.

The version of the bill passed by the House proposed removing silencers—referred to in the industry as “suppressors”—from a 1930s law that controls firearms deemed very dangerous, also eliminating a related $200 tax. However, the Senate’s version kept the regulation on silencers and expanded it to include short-barreled rifles and shotguns.

Under the National Firearms Act, potential buyers of the regulated weapons must also undergo a finger-print based background check. There is no deadline for such checks. The process is arguably more thorough than the name-based background check completed for other firearms purchases.

Lawmakers said the silencers provision was deemed by the Senate parliamentarian to be in violation of the “Byrd Rule,” which stipulates that the budget changes sought in the legislation cannot be “merely incidental” to the policy changes. The special rules are designed to deter provisions unrelated to spending or taxes from being included in the bill.

“It’s no surprise that Republicans will jump at any opportunity to please the gun lobby by rolling back gun safety measures, but that kind of policy does not belong in a reconciliation bill,” said Sen. Ron Wyden, D-Ore.

Gun rights groups complained about the $200 tax and how the background check process often takes weeks and even months for silencers and short-barreled weapons.

Larry Keane of the National Shooting Sports Foundation, who supports the legislation, said before the ruling that the proposed changes were aimed at helping target shooters and hunters protect their hearing. He argued that the use of silencers in violent crimes is rare. “All it’s ever intended to do is to reduce the report of the firearm to hearing safe levels,” Keane said.

John Commerford, executive director of the National Rifle Association’s Institute for Legislative Action, disagreed with the parliamentarian’s ruling, noting that she was originally appointed by then-Senate Majority Leader Harry Reid, a Democrat.

“Nevertheless, we remain committed to working with our allies on Capitol Hill to end the unjust tax burden on these constitutionally-protected arms,” Commerford said.

Groups opposed to the measure included Giffords, the gun violence prevention organization co-founded by former Rep. Gabby Giffords who was grievously wounded in a 2011 mass shooting in her district.

Emma Brown, the group’s executive director said “removing safeguards on gun silencers would have made it easier for violent criminals to escape, putting both law enforcement and civilians at greater risk.”

“What’s more, removing safeguards on short barreled firearms would have only enabled more criminals to access these easily concealable weapons, which can be easily brought into large crowds,” Brown said.

The gun language had broad support among Republicans and has received little attention as House Speaker Mike Johnson, R-La., and Senate Majority Leader John Thune, R-S.D., work to settle differences within the party on cuts to Medicaid and energy tax credits, among other issues.

It is just one of hundreds of policy and spending items that were included to entice members to vote for the legislation and will have broad implications in the years to come.