As President Trump moves unilaterally to slash the federal bureaucracy and upend longstanding policies, Republicans in Congress have embarked on a spree of deregulation, using an obscure law to quietly but steadily chip away at Biden-era rules they say are hurting businesses and consumers.
In recent weeks, the G.O.P. has pushed through a flurry of legislation to cancel regulations on matters large and small, from oversight of firms that emit toxic pollutants to energy efficiency requirements for walk-in freezers and water heaters.
To do so, they are employing a little-known 1996 law, the Congressional Review Act, that allows lawmakers to reverse recently adopted federal regulations with a simple majority vote in both chambers. It is a strategy they used in 2017 during Mr. Trump’s first term and are leaning on again as they work to find ways to steer around Democratic opposition and make the most of their governing trifecta of the House, the Senate and the White House.
But this time, Republicans are testing the limits of the law in a way that could vastly expand its use and undermine the filibuster, the Senate rule that effectively requires 60 votes to move forward with any major legislation.
Because resolutions of disapproval under the Congressional Review Act need only a majority vote, they are some of the only legislation that can avoid a filibuster in the Senate. This allows them to circumvent the partisan gridlock that stands in the way of most significant bills.
So far this year, Mr. Trump has signed three such measures: one overturning Biden-era regulations on cryptocurrency brokers, another canceling fees on methane emissions and a third doing away with additional environmental assessments for prospective offshore oil and gas developers. Another five, including one that eliminates a $5 cap on bank overdraft fees, have cleared Congress and await Mr. Trump’s signature.
That is a much slower pace than eight years ago, when Republicans erased 13 Obama administration rules within Mr. Trump’s first 100 days in office. Before then, the law had been successfully used only once, when President George W. Bush reversed a Clinton-era ergonomics rule.
Now Republicans are trying to go much further with the law, including using it to effectively attack state regulations blessed by the federal government. The House this week passed three disapproval resolutions that would eliminate California’s strict air pollution standards for trucks and cars by rejecting waivers from the Environmental Protection Agency that allowed them to take effect.
The move would also permanently prevent federal regulators from writing a similar rule in the future. Both the Government Accountability Office and the Senate parliamentarian, who is in charge of enforcing the chamber’s rules, have said that the E.P.A. waivers do not constitute federal regulations and thus are not subject to the Congressional Review Act.
The pressure now falls on Senator John Thune, Republican of South Dakota and the majority leader, to decide whether he will proceed with the measures anyway, sidestepping the parliamentarian in a move that would undermine the filibuster.
Mr. Thune’s decision is something of a warm-up act for an even more consequential showdown coming later in the year as Republicans try to deliver Mr. Trump’s agenda through the budget reconciliation process, another way of shielding legislation from a filibuster. G.O.P. senators already steered around the parliamentarian in early April, when they pushed through a budget blueprint that deemed the continuation of Mr. Trump’s tax cuts as cost-free, even though nonpartisan budget scorekeepers have estimated it would cost about $4 trillion over a decade.
Two spokespeople for Mr. Thune did not immediately respond to multiple requests for comment via phone or email on whether he would try to defy or otherwise circumvent the parliamentarian on the Congressional Review Act measures.
Democrats argue that Republicans’ efforts to kill the E.P.A. waivers amount to illegal overreach on states’ rights. They say the drive could inadvertently subject a plethora of executive actions, such as leasing rights for oil and gas fields as well as waivers for state Medicaid programs, to congressional review.
“House Republicans would set a dangerous precedent,” said Representative Frank Pallone Jr. of New Jersey, the top Democrat on the Energy and Commerce Committee. “That would mean countless numbers of executive actions made across the federal government would be at the mercy of the political winds of a vocal few in Congress.”
During debate this week on the measures canceling the E.P.A. waivers, Representative Zoe Lofgren, Democrat of California, said: “Abusing the Congressional Review Act is not the slope that you want to slide down.”
Republicans, on the other hand, argue that the scope of their review prerogatives should not be determined by unelected bureaucrats.
“It’s members of Congress — not the G.A.O., not the parliamentarian — who decides how we proceed under the C.R.A.,” Representative Chip Roy, Republican of Texas, said in a speech on the House floor.
Either way, experts warned that Republicans may come to regret reading the statute so broadly. Michael Thorning, the director of the Structural Democracy Project at the Bipartisan Policy Center, a nonprofit think tank, said doing so could hand Democrats a powerful tool to undo regulations that they dislike when they one day return to power.
“The more you stretch and expand these processes, you really just undermine those to the point that they could eventually become meaningless if taken to the extreme,” Mr. Thorning said.
“At the end of the day, this is Congress’s decision,” he added. “The G.A.O. and the parliamentarian are just advisers. So, you know, members will have to take responsibility for these decisions.”
When President Joseph R. Biden Jr. entered office in 2021, congressional Democrats took a cue from Republicans and reinstated Obama-era caps on methane emissions that the Trump administration spent years working to overturn through executive action.
The Republican push to take a more aggressive stance on reversing federal regulations imposed by the Biden administration comes as the party has largely ceded other legislative branch prerogatives — over spending, trade and oversight — to the Trump administration.
Some Democrats are borrowing the tactic and pressing to use the Congressional Review Act to push back on Mr. Trump’s executive actions, including his move to cull the federal work force.
Senator Jeff Merkley of Oregon and Representative Maxine Waters of California, both Democrats, have proposed a bill that would make a federal agency’s staff cut plans — including the mass layoffs known as “reductions in force” undertaken by the Trump administration — subject to congressional review.
The measure would also require agencies to justify proposed staff cuts, quantify the impact on employees and agency operations, and present any alternatives the agency considered. It has no realistic chance of surviving the Republican-controlled Congress and would certainly be vetoed by Mr. Trump,
“Mass firings are an attack on the separation of powers,” Mr. Merkley said in an interview. “These have very big impacts on the provision of services to Americans, and Congress should have a voice in that.”
Mr. Merkley criticized Republicans for using the review law to try to attack the E.P.A. waivers for California, arguing that such a move constituted a “nuclear option” aimed at carving out an entirely new set of policy matters from the Senate’s filibuster.
“If the Republicans want to expand the Congressional Review Act, they should do it through legislation, not through a bogus reinterpretation,” Mr. Merkley said. “You want to expand the scope? Propose a bill. That’s what I’m doing.”
