In what InsideClimate News is calling a “striking victory for environmental advocates” who’ve spent more than a decade fighting the project, a federal judge in Montana has ordered an immediate construction halt on the Keystone XL pipeline, after concluding the Trump administration failed to justify its executive order to restart the intensely controversial project.

“It was a major defeat for [Donald] Trump, who attacked the Obama administration for stopping the project in the face of protests and an environmental impact study,” the Washington Post reports. “Trump signed an executive order two days into his presidency setting in motion a course reversal on the Keystone XL pipeline, as well as another major pipeline, Dakota Access.”

But late last week, “environmental advocates, landowners along the pipeline’s route, and Indigenous rights groups hailed the ruling,” InsideClimate reports. “They called it a major setback—if not a permanent defeat—for the long-contested crude oil pipeline. The Obama administration had determined that the pipeline was not in the national interest, and President Barack Obama had cited its potential climate impact in rejecting it.”

“This decision vindicates what we have been saying all along: Trump’s approval of this pipeline was illegal, violated environmental laws, and was based upon fake facts,” said Indigenous Environmental Network Executive Director Tom Goldtooth.

“This is the best news we could have gotten today,” added IEN organizer Joye Braun, a member of the Cheyenne River Sioux tribe. “To have the judge affirm that what Trump did was illegal and that this pipeline would affect climate change and destroy cultural sites of my people, and that water, our first medicine, is threatened. It’s not over yet, but we are a step closer to stopping this zombie pipeline.”

Montana farmer Dena Hoff of the Northern Plains Resource Council called the 54-page ruling by District Court Judge Brian Morris “a victory for common sense stewardship of the land and water,” adding that “all Americans should be proud that our system of checks and balances can still function, even in the face of enormous strains.”

“We’re pleased and surprised by this decision,” said South Dakota landowner John Harter, chair of Dakota Rural Action. “It’s nice to have a federal judge agree with the common-sense analysis we’ve done. Basically, you just can’t reverse a decision based on environmental and scientific facts just because you feel like it.

Greenpeace Canada climate campaigner Mike Hudema said the ruling is a significant setback Keystone and a big win for Indigenous groups and environmental defenders. “This should also be huge warning sign to the [Canadian] Liberal government about the inevitable legal hurdles they will face if they continue to rush and curtail the Trans Mountain assessment process,” he told CBC in a prepared statement. “We can’t afford new fossil fuel infrastructure if we want to save the planet.”

Donald Trump, on the other hand, called the ruling “a political decision made by a judge.” He added the case will likely be appealed to the Ninth Circuit Court of Appeals, and “we’re slowly putting new judges in the Ninth Circuit.”

In his ruling, Morris took issue with Trump’s executive order to restart the pipeline. “The Trump administration, determined to make the project an early example of its no-holds-barred policy of exploiting fossil fuel resources without regard for climate consequences, had made only a perfunctory review in its quick decision to speed the work along,” InsideClimate recalls. “A full-blown review can take more than a year to complete,” and “several were done in the past decade, producing mainly controversy and delay while sharpening the climate argument against a line that was first disputed because of the risks of spills in sensitive ecosystems.”

That led Morris to conclude that the incoming administration “simply discarded prior factual findings related to climate change to support its course reversal”. The judge added that Trump failed to take a “hard look” at factors like low oil prices, the cumulative effects of greenhouse gas emissions from the Keystone and Alberta Clipper pipelines, the potential cultural resources along the route, and the risk of oil spills, InsideClimate states.

The ruling underscores the value of the U.S. National Environmental Protection Act as a tool to defend environmental and fossil fuel regulations from a deeply hostile government, ICN adds.

“The law calls for a full environmental impact analysis of any major federal action, taking into account its cumulative pollution burdens and encompassing the full sweep of its implications, which in recent decades has increasingly meant looking at the resulting buildup of carbon dioxide in the atmosphere,” writes reporter Phil McKenna. “Without doing that, the Trump administration in 2017 simply overturned the Obama administration’s refusal to approve a permit to cross the U.S.-Canadian border, greasing the skids for the 1,179-mile pipeline. Even so, the pipeline project has been held up by court battles, and work has not commenced on its northern section. A southern section, not needing a border permit, was completed years ago.”

The Washington Post adds that the ruling “highlights a broader legal vulnerability in the Trump administration’s push to roll back Obama-era environmental protections. Since Trump took office, federal courts have found repeatedly that his agencies have short-circuited the regulatory process in areas ranging from water protections to chemical plant safety operations. Robust environmental and administrative procedure laws, many dating back to the 1970s, have given the administration’s opponents plenty of legal ammunition.”

Yet “Thursday’s decision does not permanently block a federal permit for Keystone XL,” the Post adds. It merely “requires the administration to conduct a more complete review of potential adverse impacts related to climate change, cultural resources, and endangered species. The court basically ordered a do-over.”

And even then, retired TransCanada executive Dennis McConaghy predicted the ruling would be overturned by a higher court. “This would be very, very problematic and put even more pressure on the Trudeau government to get the Trans Mountain pipeline built,” he said. “Canadians should hope that this thing is vigorously litigated and reversed.”