This week, Republicans in Congress may finally have the opportunity to begin dismantling a series of environmental rules finalized by the Obama administration. And they’re likely to initially target two controversial environmental regulations released in the closing months of 2016, which place greater restrictions on both the coal and the oil and gas industries.  

The first is a regulation finalized in mid-November that seeks to curb fugitive methane emissions from oil and gas drilling operations on public lands. And the second, a last-minute rule adopted in December, prohibits coal-mining companies from engaging in any activities that could permanently pollute streams and other sources of drinking water.

The key to undoing the regulations comes in the form of a rarely used federal law known as the Congressional Review Act. The law allows Congress 60 legislative days (that means working days in session) from the time a federal regulation is finalized to pass a “joint resolution of disapproval” on the rule. If the president signs the resolution, the rule is nullified — and, furthermore, the law stipulates that “substantially” similar regulations may not ever be passed again unless specifically authorized by Congress.  

When it comes to the 60-day countdown period, though, things can get a little complicated. If a congressional session ends before the period is up — and because Congress meets sporadically, that period can sometimes drag out for months — then the law requires that the countdown begin again on the 15th day of the new session.

In this case, the previous Congress adjourned before the 60-day deadline period ended for multiple Obama-era regulations passed in the latter half of 2016. The countdown is just now starting over again this week, as Monday marks the 15th day of session for the new Congress. So now is the first time they may begin formally introducing resolutions affecting late-term Obama regulations that will be valid under the Congressional Review Act — and do so with a sympathetic president in office who is likely to sign them.

Resolutions to disapprove of the two Obama actions are already scheduled to be taken up by Congress this week. Both were hailed by environmentalists but garnered quick backlash from Republicans, who decried them as attacks on the nation’s energy. In fact, immediately upon its announcement in December, Senate Majority Leader Mitch McConnell denounced the stream protection rule and vowed to overturn it using the Congressional Review Act when the new Congress convened.

Once a joint resolution of disapproval has been introduced, it has the potential to move fairly quickly from the House to the Senate to the president. In fact, the only other time the law has been successfully used to repeal a regulation — an ergonomics rule adopted by the Clinton administration and repealed early on in the subsequent Bush administration — it moved through Congress in less than a week. This is because the law allows only up to 10 hours of debate in the House and does not permit joint resolutions to be subject to filibuster in the Senate.  

Environmental groups have already begun to speak out. One recent letter to the House, signed by dozens of environmental organizations, called on representatives to oppose any measures that would weaken or undo the stream protection rule.

“Legislation undermining the Stream Protection rule would be a direct attack on ensuring that every community has access to clean, safe water,” it states. “Furthermore, permanently blocking the rule under the Congressional Review Act and any future ‘substantially the same’ effort by the Department of the Interior is extreme and blocks the agency from doing its basic job of managing and protecting our natural resources.”  

And environmental groups have also rallied behind the methane rule, which experts have pinned as a likely target for the chopping block for weeks now. In a recent blog post, energy campaign manager Josh Mantell of the Wilderness Society called the methane rule a “smart, common-sense way to ensure that the American people see a fair return on the development of their shared resources” and called for Congress to abandon its plans for repeal.  

However, Republicans in Congress have continued to stand by their plans. In a statement on Monday, McConnell reiterated his intention to see the stream rule repealed under the Congressional Review Act, calling it a “harmful regulation that unfairly targets coal jobs.”  

“I would encourage the House to act quickly so that we can send this resolution to the president’s desk as soon as possible,” he added.