(Montana Free Press) Anti-pipeline plaintiffs presented oral arguments Thursday in Great Falls federal court in a lawsuit against the federal government seeking to revoke permits greenlighting the Keystone XL tar sands pipeline that environmental and indigenous groups say were granted based on faulty, outdated data.

District Judge Brian Morris probably won’t make a decision for months. Morris previously ruled in favor of the plaintiffs when the government tried to have the lawsuit thrown out as a presidential matter of national security, and again when the defendants tried to withhold documents concerning the pipeline’s approval.

If Morris rules in favor of the plaintiffs, the pipeline’s progress could be halted as the U.S. Department of State is forced to update the 2014 environmental impact statement the Trump administration used to justify resurrecting the project last January. Former President Barack Obama in 2015 used the same EIS to justify denying the permits to the pipeline company, TransCanada. Obama’s decision was thought to have killed the 1,100-mile pipeline designed to pump tar sands crude from Alberta to Gulf Coast refineries.

The lawsuit was brought by Northern Plains Resource Council and other environmental and indigenous rights groups, who organized an anti-pipeline march along the Missouri River to the courthouse Wednesday.

The hearing began with NPRC introducing two documents summarizing a recent ruling by the Nebraska Public Service Commission denying TransCanada’s preferred pipeline route through that state, and stipulating an alternate route. The State Department approved construction of Keystone XL based on environmental reviews of the now-nixed route, and the plaintiffs argue that since the alternate route hasn’t been assessed by the State Department, then the EIS is moot and Morris should revoke the permit to allow the border crossing.

“It rushed to approve the permit and win points with the new administration,” Sierra Club attorney Doug Hayes said. “We just don’t know what the site-specific attributes of the new site are.”

Hayes said the State Department is preparing to shoehorn in an environmental assessment of Nebraska’s alternate route after the fact by including it in a Bureau of Land Management assessment of the Montana route, which will be published Friday in the Federal Register. The BLM is also a defendant in the lawsuit.

Luther Hajek, an attorney for the government, said the Nebraska Department of Environmental Quality approved of the alternate route previously, but admitted the State Department had not yet analyzed the route, as they had no idea it was going to change eight months after the undersecretary granted the permit.

The rest of the hearing followed a similar pattern, with the plaintiff’s alleging the federal government violated the National Environmental Policy Act by relying on the 2014 EIS, and the defendants saying their actions adequately followed NEPA provisions and government protocol. Topics ranged from shifts in the global oil market, to the pipeline’s effect on climate change, to the best and most available whooping crane migration data, to the cumulative impact of individual extractive projects, and arcane circuit case law.

Plaintiffs attorney Jamey Volker said the government “eliminated any alternative that did not serve TransCanada,” and “painted itself into a corner by strait-jacketing its review,” which he called “sheer poetry” in how it ignored environmental side-effects of the pipeline.

Hajek said the Obama administration’s denial of the pipeline, which was based on the 2014 EIS, proves the assessment wasn’t written in a way that preordained approval of the pipeline.

The plaintiffs also alleged the oil spill model used in the EIS was not designed to predict the effect of pressurized pipeline spills or tar sands, which sink to the bottom of rivers, and instead measured only the possible effects of lightweight oil floating on the water’s surface.

Volked also said the EIS underestimates the threat Keystone XL poses to the Assiniboine Sioux Rural Water Supply System, a $300 million water network drawing river water from the Missouri for 30,000 Montanans on the Fort Peck Indian Reservation and surrounding communities. Congress mandated construction of the network in 2000 after decades of oil extraction resulted in portions of Northeast Montana’s groundwater becoming undrinkable due to contamination from salt and carcinogenic pollutants.

The EIS states the water system’s intake plant sits 70 miles downriver of Keystone XL’s proposed crossing of the Missouri River, a quarter mile west of the reservation’s border. The spill assessment in the document only considered effects of oil 10 miles downriver. Volker said that according to the water system’s board chairman, Bill Whitehead, the network actually has three intakes on the Missouri: 10, 14 and 50 miles downstream of the proposed pipeline crossing. Whitehead has previously said a tar sands leak would destroy Fort Peck’s new water supply system, which came fully online in 2015.

“You can’t just put your thumb on the scale and say ‘everything is rosy’ anymore,” Volker said, speaking on the economic cost of continued fossil fuel development and climate change.

The defense appeared blindsided by news of multiple water intakes.

“I’m not sure if that’s accurate,” Hajek said. “That’s not something we were able to ascertain.”

Hajek said the information was extra-legal as it had not been submitted, and should not be used to rule on anything. Morris did not comment on that argument.

“The plaintiffs have thrown everything at the wall just to see what sticks,” TransCanada attorney Peter Steenland said, claiming the National Environmental Policy Act is not applicable in this case, and that any case law the defense cited saying otherwise is wrong.

In his closing argument, Steenland, a former career DOJ environmental attorney turned energy industry lawyer, noted that the government has won all 17 NEPA cases that have gone on to the U.S. Supreme Court. He advised Morris to follow established jurisprudence.

Morris replied by calling NEPA a unique statute that has provided livelihoods for a lot of attorneys.

Steenland said projections that Keystone XL will begin construction in Montana in September are wishful thinking, as TransCanada is still awaiting BLM right-of-way and Army Corps of Engineers waterway permits. However, mowing, road work and storage of pipeline materials should begin this fall, he said.

Joy Braun, a Cheyenne River Sioux member of the Indigenous Environmental Network, another plaintiff, said after the hearing that “mowing” and other upcoming pipeline activities still affected cultural sites, including the burial sites of her ancestors.

Even though the tribes aren’t involved in the lawsuit, Fort Peck tribal tribal attorney Majel Russell said in an email earlier this month that the tribal government still opposes the Keystone XL pipeline. Russell said the tribe is still waiting to see federal action on the BLM and Army Corps permits.

“The Pipeline does not currently have all of the necessary federal approvals and the Tribes’ continue to consider all of their legal options as the permitting process moves forward,” she said.

Whitehead said negotiations last year between TransCanada and the tribal government to potentially reroute the pipeline downstream of their water intake came to nothing.

“It would help us, but what would happen downstream?” Whitehead said, adding that tribes downriver of the Fort Peck Sioux and Assiniboine are watching to see if they’ll take a stand.

Hunter Pauli is a freelance reporter based out of Missoula. He has reported for the Montana Standard in Butte, the Missoula Independent and the Montana Native News Project. This article was originally published on the Montana Free Press.