The Senate failed to repeal an Obama-era rule limiting the release of methane from drilling on lands overseen by the U.S. Bureau of Land Management, or BLM, on Wednesday. For now, at least, the climate-focused rule will stand as law.

The 51-49 vote is the first time that this Congress has failed to repeal a law under the Congressional Review Act, or the CRA, a 1995 law that allows for Congress and the president to permanently erase regulations issued by a federal agency. Once a rule is undone by the CRA, a similar rule on the same topic can never be proposed again.

Republican Senators John McCain, Lindsey Graham, and Susan Collins joined with every Democratic and independent senator to vote against the measure.

Collins and Graham were previously known to oppose repealing the rule, but McCain’s no vote was a surprise. After the vote, he said that he opposed the measure due to the permanent nature of the CRA.

“While I am concerned that the BLM rule may be onerous, passage of the resolution would have prevented the federal government, under any administration, from issuing a rule that is ‘similar,’ according to the plain reading of the Congressional Review Act,” McCain said in a statement.

The rule prohibited the excessive release of methane gas from drilling projects on public and tribal lands overseen by the Bureau of Land Management.

The Department of the Interior has found that enough natural gas was “vented” from public-land drilling projects between 2009 and 2015 to power more than 6 million homes for a year. The Environmental Defense Fund has also estimated that $330 million in natural gas is lost every year on BLM fracking sites.

The rule was also one of many Obama-era rules meant to reduce U.S. greenhouse-gas emissions so as to mitigate climate change. Though it only remains in the atmosphere for about 12 years, methane is a much more powerful greenhouse gas than carbon dioxide, trapping at least 25 times as much heat. A study published in the Proceedings of the National Academy of Sciences earlier this year argued that methane released into the atmosphere today will continue to raise sea-levels for another 800 years.

Between 2007 and 2014, methane levels in the atmosphere have spiked worldwide. Though this surge has occurred at the same time as the global fracking boom, scientists say it is still unclear that the two are connected.

It’s rare for a vote to fail once brought to the floor by party leadership, but Mitch McConnell, the Senate majority leader, was working under a tight deadline. Under the CRA, Congress can only repeal rules adopted in the past 60 legislative days—that is, days when Congress is in session. For the methane rule, that period expires on Thursday, after which Congress could not move the measure further.

Congress has already repealed 13 Obama-era regulations so far this year. It has allowed mining companies to dump toxic coal ash in mountain streams, hunters to kill bears and wolves in Alaska while they hibernate in their dens, and internet companies to collect and sell consumer information without their permission.

The repealed rules represent some of the most substantive legislative accomplishments by the Trump administration and the Republican-controlled Congress so far.

While the methane rule will stand as law for now, it still faces legal challenges. A case challenging the rule is being heard in federal district court in Wyoming. The Bureau of Land Management could also opt to review the rule again on its own terms, though this would generate another rule-making process, giving the public and environmentalists opportunity to intervene. Finally, the Trump administration could choose to weakly enforce the rule—but that strategy would only work as long as that administration holds power.