Methane emissions, guns, river pollution, Wall Street: hand in hand with President Donald Trump, the Republican majority in Congress has begun to repeal Obama-era regulations opposed by big business.

At the very beginning of his term, the billionaire Republican president signed an order freezing any new regulations close to being finalized, and requiring that for each new rule imposed two others must be eliminated.

"We think we can cut regulations by 75 percent, maybe more," Trump said in a White House meeting with business leaders on January 23.

If details remain vague (75 percent of the number of pages in regulations? 75 percent of cost?), they reflect the clear intent of the Republican majority to satisfy the demands of the interest groups that have invested hundreds of millions of dollars in lobbying and campaign donations.

"Every day is Christmas for big business in the Trump administration," Robert Weissman, president of Public Citizen, told AFP. His nonprofit advocacy group is filing a court challenge to the order on regulations.

In practice, Trump can delay such regulations -- which have passed through a years-long review process -- but he cannot eliminate them with the simple stroke of a pen.

Republican leaders in Congress, however, have unearthed a rarely used 1996 law that allows them, through a vote, to revoke certain regulations finalized in the last six months of the previous administration.

They have already targeted for repeal:

- a rule that would have made it harder for mining companies to dump coal-mining waste into streams and waterways;

- an anti-corruption rule requiring oil, gas and mining companies to disclose any payments made to foreign governments, including taxes and royalties;

- a rule to require oil and gas companies drilling on public lands to reduce leaks or burnoff of methane, a heat-trapping gas linked to global warming; and

- a rule aimed at keeping firearms out of the hands of certain mentally disabled people.

Trump, for his part, has signed an executive order targeting the sweeping Dodd-Frank financial reform adopted after the recession of 2008, as well as the so-called fiduciary rule that requires financial advisers to act in the interest of their clients.

The objective in each case is the same: less regulation means fewer costs for companies, and, they say, for consumers.

- Permanent resistance -

These rules were targeted by powerful business organizations like the US Chamber of Commerce and Freedom Partners, which accused the Obama administration of imposing excessive costs on companies, particularly through tough new environmental rules.

Landmark regulations like those in the Clean Power Plan, which would compel coal-fueled power plants to slash their carbon emissions, are also being tested in court.

"The last eight years have been a challenge," said Paul Schlegel, director of environment and energy policy for the American Farm Bureau Federation. Farmers now have a feeling of "hope," he told AFP.

Dozens of business groups from every sector of the economy are now piling pressure on Congress to weaken the power of federal agencies.

"The signals that are being sent by the Trump administration about regulatory reform are things that we would support," said Lowell Randel, vice president of the Global Cold Chain Alliance, which represents 1,300 companies involved with refrigerated storage and transport.

The Trump administration may also choose to act more favorably on the enforcement side, possibly reducing on-site safety and quality inspections, or instructing federal agencies to issue warnings but fewer fines. The enforcement division of the Environmental Protection Agency might even be shuttered, according to the Inside EPA website.

"We don't expect leniency, but if there is a greater degree of constructive engagement, we think that would be a positive step," said Schlegel of the farm group.

With Democrats now the minority party in Congress, resistance to deregulation will likely be led by nonprofit groups advocating for the environment and consumer protection.

The next four years could see the emergence of a more or less permanent resistance movement, with the courts as a favored battlefield.

"There will be legal challenges to every repeal," predicted Rebecca Buckwalter-Poza, of the Center for American Progress, a left-leaning think tank.

"There are going to be a lot of hurdles, but in the meantime things will not be enforced, and it will not be possible to make new rules."