A group of Democratic state attorneys general on Tuesday slammed President Donald Trump’s executive order directing the Environmental Protection Agency and the Army Corps of Engineers to consider rolling back a regulation aimed at protecting America’s waterways from pollution.

“We strongly oppose President Trump’s action today that undermines Clean Water Act protections and the public health and environment of our states,” the attorneys general in New York, Hawaii, Massachusetts, Oregon, Vermont and the District of Columbia said in a statement.

The group of attorneys general, led by New York Attorney General Eric Schneiderman (pictured above), hinted they could take legal action against the Trump administration.

“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,” they wrote.

The “Waters of the U.S. rule,” as it’s known, lays out which bodies of water the federal government can work to protect from pollution under the Clean Water Act, but was put on hold by a federal appeals court.

The attorneys general wrote that the executive order “runs counter” to the EPA’s effort in “achieving clean water.”

“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,” they wrote in the statement.