During his first address to a joint session of Congress last night, President Trump promised to "work with members in both parties" to, among other things, "promote clean air and clear water." Hours earlier, he signed an executive order to begin rolling back an Obama-era anti-pollution rule that gave the government regulatory control over waterways.

The White House's press release about the order is titled, "Presidential Executive Order on Restoring the Rule of Law, Federalism, and Economic Growth by Reviewing the 'Waters of the United States' Rule." After Trump's election victory, National Geographic broke down the issue:

The Clean Water Act of 1977 is a lynchpin in U.S. environmental policy and the country’s main law governing water pollution. The law applies to “navigable waters,” which it defines, unhelpfully, as “waters of the United States.” The argument about what that means has stretched over nearly four decades and three Supreme Court decisions.

The Trump campaign’s official transition website, greatagain.gov, makes clear that the incoming administration will attempt to roll back the Obama Administration’s effort to clarify the matter.

In 2006 the Supreme Court ruled in Rapanos v. United States that the Clean Water Act also applies to waters that have a “significant nexus” with navigable rivers or seas. The “Waters of the United States” rule issued last year by the EPA interprets that as extending the federal government’s jurisdiction to streams, including seasonal ones, that flow into navigable rivers, and also to wetlands located near such streams or rivers.

The EPA argued that the move was scientifically justified, as the quality of navigable waters downstream depends heavily on water quality upstream—polluted water, like clean water, flows downhill.

The oil and gas industry was not so happy when President Obama signed the revised rule—and they were thrilled yesterday. As was the farming industry, who worried that they would also be regulated. Trump said during the signing, "It was a massive power grab. EPA regulators were putting people out of jobs by the hundreds of thousands and regulations and permits starting treating our wonderful small farmers and small businesses as if they were major industrial polluters. They treated them horribly, horribly. If you want to build a new home for example you have to worry about being hit with a huge fine if you fill in a puddle, just a puddle."

In response to the order, Bob Irvin, president of American Rivers, said, "Without the Clean Water Rule’s critical protections, innumerable small streams and wetlands that are essential for drinking water supplies, flood protection, and fish and wildlife habitat will be vulnerable to unregulated pollution, dredging and filling."

NY Attorney General Eric Schneiderman blasted the Executive Order in a statement on behalf of himself and the attorneys general of New York, the District of Columbia, Hawaii, Massachusetts, Oregon, and Vermont:

"We strongly oppose President Trump’s action today that undermines Clean Water Act protections and the public health and environment of our states.

The President’s order runs counter to the Clean Water Act’s, and the EPA’s, very purpose: achieving clean water. The Clean Water Rule is a measured, reasonable, and lawful application of sound and uncontroverted science to protect our nation’s upstream source waters. We rely on these waters to ensure clean drinking water, recreation, and viable commercial fishing and navigation. Abandoning the Clean Water Rule will allow uncontrolled pollution of these critical water resources. It could also harm the competitiveness of our state economies by forcing us to spend more to clean up the pollution of deregulated waters coming from upstream states that refuse to control such pollution.

Clean water is essential to life -- and the people of our states and the nation deserve the basic protections established by the Clean Water Rule, to ensure that the benefits of clean water are shared equally, regardless of state lines.

We won’t hesitate to protect our people and our environment—including by aggressively opposing in court President Trump’s actions that ignore both the law and the public’s paramount need for clean water.”

The NRDC said yesterday

, "Although the Trump administration has targeted the Clean Water Rule for repeal, today's action does not kill it. Repealing a rule requires a full public process. It has to be justified by the law and the evidence available. That’s going to be rough sledding for the new administration, because the rule relies on an extensive scientific record and its protections are easily consistent with what Congress required in the Clean Water Act."