With everything that Republicans want to do — repeal Obamacare, overhaul the tax code — it might seem odd that one of Congress’ very first acts would be to kill an obscure Obama-era regulation that restricts coal companies from dumping mining waste into streams and waterways.

But that is indeed what’s going on. In early February, the House and Senate voted to repeal the so-called “stream protection rule” — using a regulation-killing tool known as the Congressional Review Act. On Thursday, President Trump signed the bill, which means the stream protection rule is now dead. Coal companies will have a freer hand in dumping mining debris in streams.

Killing this regulation won’t exactly fulfill Trump’s goal of reversing the coal industry’s decline; that decline has more to do with cheap natural gas than anything else. Instead, Republicans are mostly focusing on this rule because they can. Because the stream protection rule wasn’t finished until very late in 2016, it’s much, much easier to kill than most of the other Obama-era rules around coal pollution. It was a ready target, so long as the GOP acted fast.

What Obama’s “stream protection rule” actually does

Coal mining is a messy business. In parts of West Virginia, Kentucky, and Virginia, mining companies often get at underground coal seams by blowing up the tops of mountains — a process known as mountaintop removal mining. Once that’s done, they’ll dump the debris into the valleys below, which can contaminate streams and waterways with toxic heavy metals.

Appalachian Voices, an environmental group, estimates that coal companies have buried over 2,000 miles of streams in the region through mountaintop removal mining since the 1990s. And there’s growing evidence that when mining debris and waste gets into water supplies, the toxic metals can have dire health impacts for the people and mostly rural communities living nearby.

In theory, there’s a law to mitigate this. The 1977 Surface Mining Control and Reclamation Act says that mining companies should not cause "material damage to the environment to the extent that it is technologically and economically feasible." But that language is vague. And the agency responsible for enforcing this law, the Office of Surface Mining Reclamation and Enforcement (OSMRE), hasn’t clarified what this all entails since publishing the “stream buffer zone rule” in 1983.

Community groups across Appalachia and environmentalists had long pushed to update the regulations here, especially since mining practices have changed drastically over the past three decades and scientists have learned more about the harmful effects of water pollution from coal mining. In 2008, the George W. Bush administration published an update to the stream buffer zone rule, but those efforts later got struck down in court for running afoul of the Endangered Species Act.

So enter the Obama administration. Ever since 2009, OSMRE has been trying to update its guidance here. That process involved poring through reams of research on the effects of coal mining on ecosystems, holding endless hearings, talking to various stakeholders, and so on.

The final rule got published on December 19, 2016 — just before Obama left office. And while it’s almost ludicrously complex, updating hundreds of older regulations, it basically puts a couple of key restrictions in place for coal companies seeking permits to expand or start new mines in the future:

First, a company that wants to open a surface or underground mine needs to avoid causing damage to the “hydrologic balance” of waterways outside of its permit area. The rule goes into excruciating detail on what these definitions mean, but it’s basically a much stricter limit on dumping waste and debris in surrounding ecosystems. Second, companies and regulators have to do a baseline assessment of what nearby ecosystems look like before any new mining begins. They then have to monitor affected streams during mining, and the company has to develop a plan for restoring damaged waterways to something close to their natural state after mining is done.

This sounds basic, but the rule-making process involved numerous debates over best how to define “hydrologic balance,” how exactly to monitor waterways, how to deal with the variety of coal industry practices out there, and so on.

In the end, environmentalists weren’t thrilled with the rule — many groups didn’t think it went far enough to restrict the dumping of debris, and they don’t believe coal companies can restore damaged streams fully to their prior state after mining. But on balance, they thought the rule a vast improvement over the status quo. An outside analysis estimated the rule would improve water quality in 263 miles of streams each year between now and 2040.

“The rule doesn’t address all the problems with the most destructive mining practices,” says Thom Kay of Appalachian Voices. “But it makes it a little bit harder for coal companies to pollute streams. And it makes it a little easier for communities to fight back against mines if they don’t want them.”

How the stream protection rule became so controversial

But coal companies loathe this new rule. Coal mining is already facing a vicious decline in Appalachia — partly because the industry is shifting West to places like Wyoming, but also because the advent of cheap natural gas has displaced US demand for coal, causing hundreds of coal power plants to close nationwide. And now comes a complex new regulation, imposing new restrictions and making it more expensive to operate.

The National Mining Association, an industry trade group, says the stream-protection rule would put more than half the nation’s untapped coal reserves off-limits to future mining — further crippling a wounded industry. The group would prefer environmental protections handled at the state level (where, in states like West Virginia and Kentucky, regulators have a much lighter touch). “It’s a pure expression of all that ordinary Americans loathe about rule by bureaucracy,” writes NMA’s Luke Popovich.

Other coal companies, like Ohio-based Murray Energy, complained that the new rule could outlaw popular techniques like longwall mining — which involves using machines with revolving blades to cut coal from an underground seam into slices. "This unlawful and destructive rule is nothing but a thinly veiled attempt to destroy our nation’s underground coal mines and put our nation’s coal miners out of work," said Robert Murray, the CEO of Murray Energy, after the rule was finished.

OSMRE, for its part, insisted that these worries were (mostly) overblown. The agency pointed out that most longwall operations are so deep underground that they wouldn’t have much effect on streams above — and hence are unlikely to be affected by the regulations. But the agency did agree the rule would make certain mining projects uneconomic and reduce annual coal employment by 124 jobs between now and 2040, thanks to lower production. (For context, the industry has lost 25,000 jobs since 2012, much of that due to continue automation and lower demand.)

Whatever the precise economic impact, the rule took on a life of its own in political debates. On the campaign trail, Donald Trump talked about reviving America’s coal industry and ending Obama’s “war on coal,” blaming rules like this for the industry’s decline. After the election, Robert Murray — one of Trump’s staunchest supporters — talked about killing the stream protection rule as a top priority. The rule featured prominently on Trump’s transition website.

Why it was so easy for Republicans to kill this particular rule

Now, the stream protection rule was hardly the only regulation that the Obama administration slapped on the coal industry. Over the past eight years, the Environmental Protection Agency has taken sweeping steps to cut air pollution from coal power plants, adding to the industry’s woes. Combine that with the glut of cheap natural gas from fracking, and coal production has plummeted:

Trump wants to overturn many of those other EPA rules as well. The trouble is that most of them are tricky to repeal. He’d have to go through the agency’s rule-making process, which would take years and face lawsuits from environmental groups.

But the stream protection rule is different. Because it took so long to complete, and because it was only finalized in December 2016, it can be easily overturned by Congress via the 1996 Congressional Review Act (CRA).

The CRA basically says the House and Senate can kill any recently finalized regulation with simple majority votes in both chambers, so long as the president agrees. What counts as “recently finalized” gets complicated, but Congress can basically vote to overturn any Obama-era regulation that was finished after mid-June 2016 — a list that spans more than 50 major regulations.

The stream protection rule happens to be the one coal rule on this list. It’s not the biggest problem facing the coal industry. But it’s procedurally simple to repeal, and Democrats in the Senate can’t filibuster CRA votes. As long as Republicans moved quickly, they could nix it quickly and easily. So that was that. Mining waste became one of the first orders of business in the new Congress.

Further reading

— Regulations around coal mining will now default to the previous 1983 stream buffer zone rule, which “has historically been applied in a manner that allows mining through streams and the construction of excess spoil fills and coal mine waste disposal facilities in perennial and intermittent streams.”

— Here’s more detail on how the Congressional Review Act works. Note that Congress has voted to kill at least eight different Obama-era regulations, including a rule that would require oil companies to disclose payments to foreign governments. (That latter is a rule that new Secretary of State Rex Tillerson once lobbied against.)

— Here’s a closer look at why Trump will struggle to save the US coal industry even if he manages to repeal many of Obama’s environmental policies. Scrapping the stream protection rule might help boost the bottom lines of some mining companies at the margins, but it’s unlikely to reverse the long inexorable downward trend of mining jobs in Appalachia.