Sens. Rand Paul, Ted Cruz and Mike Lee may be out of luck in their quest to prevent the Senate from taking up gun control legislation.

In a letter to Majority Leader Harry Reid, D-Nev., the three conservatives — from Kentucky, Texas and Utah, respectively — announced opposition to moving on gun violence legislation when the Senate returns from the two-week spring recess.

Paul, Cruz and Lee may already know that their desire to filibuster the bill could be short-circuited by the Senate’s new rules, adopted in January. The plain language of the letter does not make any reference to a time-consuming procedural motion known as cloture, which would require the support of 60 senators for Reid to prevail on his motion to overcome a filibuster.

“We will oppose the motion to proceed to any legislation that will serve as a vehicle for any additional gun restrictions,” the senators wrote.

While motions to proceed have often faced a supermajority procedural vote, the Senate’s revised rules and procedures allow Reid to proceed to legislation without the threat of a pre-emptive filibuster under a new process that guarantees votes on two amendments for each party. Under those rules, Reid could not immediately deploy a long-established procedural trick known as filling the amendment tree to preclude GOP proposals he finds unpalatable from getting floor votes.

After the Republicans and Democrats each offer two amendments, it seems that the Senate would then return to the method of operation common in recent years, with senators allowed to offer additional amendments unless and until Reid makes procedural moves to turn off the spigot. That could include filling the amendment tree once each party has had their two votes or filing a motion to end debate on the underlying bill. Indeed, nothing in the new rules would prohibit Paul, Cruz, Lee or any other senator from mounting a filibuster of the bill before passage.

A senior Democratic aide would not rule out Reid using the new rules to force gun control to the floor, saying that every procedural option is on the table.

But both Reid and other gun control advocates have already hinted that the two-amendment rule may be in the offing.

“There will be at least two amendments, probably more. One offered by Sen. Feinstein that will propose the assault weapons ban and a prohibition on high-capacity magazines, 10 bullets or more.” Sen. Richard Blumenthal, D-Conn., said on MSNBC recently. “There will be a second amendment that will prohibit high-capacity magazines, separate from the first, in other words, splitting out that measure.”

In his March 21 statement, Reid name-checked both the assault weapons ban promoted by Dianne Feinstein, D-Calif., and some version of new restrictions on high-capacity magazines championed by Sen. Frank R. Lautenberg. D-N.J.

While Blumenthal and many other Democrats favor reviving the ban on assault weapons, Reid has publicly doubted whether even 40 senators actually support such a measure. Nonetheless, the more liberal Democratic bloc intends to keep pushing for at least a vote.

Paul, Lee and Cruz, however, cite constitutional concerns with the legislation moving forward, including, it seems, with expanded background checks.

“We, the undersigned, intend to oppose any legislation that would infringe on the American people’s constitutional right to bear arms, or on their ability to exercise this right without being subjected to government surveillance.”

The letter was signed by the trio the day after Reid announced plans to queue up a firearms package that includes provisions to combat gun-trafficking, provide increased school safety and require enhanced background checks.

Reid spokesman Adam Jentleson expressed incredulity at the Republicans’ opposition to debating a gun control bill.

“While this threat is entirely unsurprising, it’s outrageous that these senators are unwilling to even engage in a debate over gun violence in America,” Jentleson said. “No matter your opinion on this issue, we should all be able to agree with President Obama when he said that the children and teachers of Newtown, along with all other Americans who have been victims of gun violence, at least deserve a vote.”