A federal judge on Monday threw out a major Trump administration rule scaling back federal protections for streams, marshes and wetlands across the United States, reversing one of the previous administration’s most significant environmental rollbacks.

U.S. District Court Judge Rosemary Márquez wrote that Trump officials committed serious errors while writing the regulation, finalized last year, and leaving it in place could lead to “serious environmental harm.”

A number of business and farm groups had supported the push to replace Obama-era standards with the Navigable Waters Protection Rule, on the grounds that states were better positioned to regulate many waterways and the previous protections were too restrictive.

The ruling in the U.S. District Court for the District of Arizona, which applies nationwide, will afford new protections for drinking water supplies for millions of Americans and thousands of wildlife species that depend on America’s wetland acreage.

Márquez, a Barack Obama appointee, noted that the U.S. Corps of Engineers, which oversees permits to dredge and fill waterways under federal jurisdiction, determined that three-quarters of the water bodies it reviewed between June 22, 2020, and April 15, 2021, did not qualify for federal protection under the new rule. Federal agencies identified 333 projects that would required a review under the Obama rule, she added, but did not merit one under the Trump standards.

“We are reviewing the ruling,” said Environmental Protection Agency spokesman Nick Conger, who declined to comment further.

The decision underscores the extent to which legal fights are shaping environmental policy across the country. Just this month the Interior Department said it would resume auctioning off new oil and gas leases to comply with an order by a Louisiana federal judge while another federal judge blocked a controversial oil project planned for Alaska’s North Slope.

Homebuilders, oil drillers and farmers – who have long argued that earlier restrictions on developing land made it too difficult to do their work – are sure to challenge the new ruling.

In June, the Biden administration announced it would write its regulations to strengthen wetland protections, but would keep the Trump-era rule on the books while it did so. But tribal and environmental groups pressed the court in Arizona to vacate the previous administration’s rule sooner.

“We came in and said, ‘No, no, no, no, you can’t leave this in place,” said Janette Brimmer, a senior attorney for Earthjustice, which represented the Native Americans and green groups in court. She added: “This is hugely good.”