A group of 12 Congressional Republicans sent a letter to the leaders of both houses of Congress Thursday, objecting to a provision in the tax bill that would allow drilling in the Arctic National Wildlife Refuge.

“For decades, Congress has voted to prohibit oil and gas development in the refuge, with the overwhelming support of the American public,” the group wrote. “Support for this protection remains strong today. After years of debate, the Arctic refuge stands as a symbol of our nation’s strong and enduring natural legacy.”

The letter was sent as the Senate was poised to pass a massive—and controversial—tax overhaul, which has seen fierce opposition from Democrats. The House passed its own version of the tax bill in November, and the two versions will now have to be reconciled. Tucked into both bills is a provision that would allow for the opening of a 1.5 million-acre section of the Arctic National Wildlife Refuge to oil and gas drilling. The justification for its inclusion in the tax bill is that profits from any oil and gas development would help offset a budget deficit.

This part of the refuge, known as the coastal plain, occupies murky legal territory and has been fought over for decades. While the majority of the 19 million-acre refuge has been designated as wilderness area—and is permanently off limits to drilling—the coastal plain has occupied a middle ground. It is not currently open to drilling, but an act of Congress could reverse that.

This is not the first time the GOP has come close to passing a bill to open this part of the wildlife refuge to drilling, but in the past, conservationists have won. This time—despite the effort of this group of Republicans—that’s looking less likely.

Earlier this week, the bill hit a procedural bump due to some arcane legislative rules that appeared to make it illegal to wrap the ANWR provision into the tax overhaul. Those who oppose drilling in the refuge saw it as a potential way to kill the provision, but Sen. Lisa Murkowski (Alaska)—a supporter of drilling in the coastal plain—said she did not see it as a problem. “We will be able to resolve all this,” Murkowski said. “I am not concerned.”

The letter opposing drilling was signed by Republican Reps. Brian Fitzpatrick (Penn.), Dave Reichert (Wash.), Ryan Costello (Penn.), Frank LoBiondo (N.J.), Chris Smith (N.J.), Patrick Meehan (Penn.), Daniel M. Donovan, Jr. (N.Y.), Elise Stefanik (N.Y.), Mark Sanford (S.C.), Carlos Curbelo (Fla.), John J. Faso (N.Y.) and Leonard Lance (N.J.).  

In it, the Republicans laid out a number of reasons why they believe drilling in the refuge is a bad idea:

• “The resources beneath the Coastal Plain simply are not necessary for our nation’s energy independence,” they wrote. “If proven, the estimated reserves in this region would represent a small percentage of the amount of oil produced worldwide.”
   
• For oil companies interested in increasing development in the U.S. Arctic, they write, a more likely scenario would have them turning to the National Petroleum Reserve, a 23.5 million-acre area west of the refuge that is designated for development and is close to existing oil and gas infrastructure.
   
• If Congress opened up the area to drilling, they warn, “the likelihood that lawsuits would accompany any development is high.”

This wasn’t the only letter sent by prominent Republicans this week. On Tuesday, a group of seven Republican luminaries, including EPA administrators under presidents Nixon, Reagan and George H. W. Bush, sent a letter of their own to the House and Senate.

They argue that how the measure to open ANWR to drilling is being pushed through is wrong.

“Decisions regarding oil and gas exploration should be made in the context of a bipartisan, broadly supported national energy policy that takes account of the need to reliably fuel economic prosperity while addressing environmental and national security challenges,” they wrote.

[Update: Congress passed the final tax bill on Dec. 20, with the ANWR drilling provision included. Of the 12 Republicans who signed the letter, six voted against the tax bill: Donovan, LoBiondi, Smith, Stefanik, Faso and Lance. The others—Fitzpatrick, Reichert, Costello, Meehan, Sanford and Curbelo—voted in favor.]