After Hurricane Katrina devastated the Gulf Coast in 2005, President George W. Bush declared a national emergency to do something Republicans had long wanted to do anyway: He suspended prevailing wage laws on federal contracts to rebuild the region.

Labor unions protested. Democrats signed on to a bill to rewrite the law. Even dozens of moderate Republicans asked Bush to reconsider.

But then a single congressman used a parliamentary maneuver – never attempted before or since – to challenge the underpinnings of the national emergency itself.

Bush backed down without even a vote.

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The largely forgotten story of Bush's capitulation explains why Republicans have advised President Donald Trump against bypassing Congress and invoking a national emergency to build a wall along the Mexican border.

In addition to raising legal questions – such a move would inevitably be challenged in court – a declaration would invite Congress to exercise its long-dormant power to revoke national emergencies.

And all it would take is one member of Congress to force the issue.

In 2005, that member was Rep. George Miller, a California lawmaker who was the top Democrat on the House Education and Labor Committee.

Calling Bush's decision "callous and misguided," Miller's first move was to try to amend the Davis-Bacon Act of 1931. That law sets the prevailing wage for federal contracts, but allows the president to grant waivers in times of national emergency.

But Democrats were in the minority, and while some Republicans were grumbling about Bush's move, they were unwilling to sign on to Miller's legislation – meaning it would never get to the House floor.

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So Miller changed tack. He dug up the National Emergencies Act of 1975, one in a series of post-Watergate reforms. It allowed Congress to terminate a presidential emergency by simple majority vote.

Republican leadership couldn't block the vote: Under the law, they had 15 business days to bring it out of committee and to the floor.

Miller introduced his resolution on Oct. 20,and a vote was scheduled for Nov. 8.

On Oct. 26, the Bush administration announced it would terminate the emergency effective Nov. 7.

Bush Labor Secretary Elaine Chao said the administration had re-examined the issue and discovered that it wouldn't save as much money as initially forecast. (Chao is now Trump's transportation secretary, and her husband is Republican Senate Majority Leader Mitch McConnell.)

Miller declared victory.

"Let me be clear," he told The New York Times. "The president is backing down today only because he had no other choice."

Mark Zuckerman, who was the Democratic staff director of the House Education and Labor Committee at the time, says all it took was the threat of a vote.

"It can be revealing when you make people vote on something," he says.

"We thought it was an unacceptable and inappropriate use of emergency powers, but we also wanted to check to see if there was really Republican support for something like this. I think it’s part of the genius of the procedure is that it tests sentiment on Capitol Hill for your unilateral idea."

The original intent of the 1975 law was to allow Congress a block a presidential emergency by simple majority vote. But in 1983, the U.S. Supreme Court struck down the legislative veto. So now, any joint resolution by Congress to terminate an emergency can be vetoed by the president.

And McConnell said Trump could do exactly that.

"The president could win anyway by vetoing the bill and then trying to get enough votes to sustain it, so may ultimately be able to prevail on the national emergency alternative," McConnell told Fox News on Tuesday.

Still, some GOP senators are already expressing discomfort over such a vote, and have asked Trump this week – both publicly and privately – not to put them in that position.

"It's not my preferred choice," said Sen. John Kennedy, R-La.

"I hope he doesn't do it," said. Sen. John Cornyn, R-Texas.

"It might be a – you know – a tough vote to win here in the Senate," said Sen. John Thune, R-S.D.

One concern is the precedent such a declaration would set.

"I think most Republicans will tell you that we really would like to find a way to avoid that type of a discussion if at all possible because this goes beyond just this president," Sen. Mike Rounds, R-S.D., told CNN on Wednesday. "This goes on to future presidents and what they might decide to declare an emergency for."

Special report:America's perpetual state of emergency, from Jimmy Carter to Barack Obama

That was exactly what Congress expected when it voted overwhelmingly to pass the National Emergencies Act.

The law called for every emergency to be reviewed – and possibly voted on – every six months. But in 44 years, presidents have declared at least 60 national emergencies without Congress taking a single vote.

Thirty-one of those emergencies remain in place today.

More:A permanent emergency: Trump becomes third president to renew extraordinary post-9/11 powers

The use of emergency powers became so routine that the Obama administration said in 2015 that they were mere formalities – despite their boilerplate language that they're in response to an "unusual and extraordinary threat to the national security." And presidents seem to have ignored requirements that they update Congress on the costs of those emergencies.

More:The Obama White House claimed that national emergencies were just formalities

Liza Goitein, director of the national security program at the Brennan Center for Justice, has advocated reforms to presidential emergency powers.

"I think Congress has woken up to the idea that the process for declaring emergencies is too permissive," she says.

"This isn’t going to look good if the Republican Senate is voting to curtail the president's power. It’s going to split Republicans and force Republicans to take a vote they don’t want to take – and it may not go Trump's way."

Trump did not mention the national emergency in his State of the Union address Tuesday, but says he's still considering it. A national emergency could allow him to transfer unspent military construction funds toward a wall.

"I don't like to take things off the table," Trump told CBS in a pre-Super Bowl interview. "It's that alternative. It's national emergency, it's other things and, you know, there have been plenty national emergencies called."