Conservative justices and some of the court's liberals seemed uneasy with the proposition that no federal agency could approve a right of way on federal land when the 2,200-mile trail traverses it.
That would create an "impermeable barrier to any pipeline from the area where the natural gas, those resources are located and to the area east of it where there's more of a need for them," Chief Justice John Roberts told Michael Kellogg, who represented the environmentalists.
At issue is the proposed Atlantic Coast Pipeline, which would begin in West Virginia and cross some of the most mountainous scenery in central Virginia before completing its 600-mile path in North Carolina.
Work in Virginia has been halted for more than a year as the builders contend with a host of setbacks handed down by federal courts. But none is more crucial than the question being considered by the Supreme Court: whether the U.S. Forest Service has authority to grant the pipeline right of way under the Appalachian Trail in the George Washington National Forest.
A panel of the U.S. Court of Appeals for the 4th Circuit threw out a Forest Service permit in December 2018, saying federal law prohibits any agency from allowing a pipeline on "lands in the National Park System."
Unless that decision is reversed, said Justice Department lawyer Anthony Yang, representing the Forest Service, "the whole enterprise is done. We're done. They have to start over."
Yang made a distinction between the trail, which is administered by the National Park Service, and the land over which it passes, which is controlled by the Forest Service.
Enter the metaphysical.
"It's a difficult distinction to wrap one's head around, Mr. Yang," said Justice Elena Kagan. She added later: "When you walk on the trail, when you bike on the trail, when you backpack on the trail, you're backpacking and biking and walking on land, aren't you?"
But Justice Samuel Alito said there was another way to think about it.
"When I think of a trail, I think of something that is on top of the earth," he said. "And when I think of a pipeline that is 600 feet below the surface, that doesn't seem like a trail. So instead of having to draw this distinction between the trail and the land, why can't we just say that the trail is on the surface and something that happens 600 feet below the surface is not the trail?"
That view seemed to also appeal to Justice Stephen Breyer.
Washington lawyer Paul Clement, representing the companies that want to build the pipeline, said his clients would be happy to win under such a theory. But he said there were other cases, not involving pipelines, that make it important for the court to recognize that an agency other than the National Park Service controls the public lands on which the trail is located.
"I don't really think it's as metaphysical as you think," Clement said to the justices. "I mean, the philosophers at the Park Service and the Forest Service haven't had any problem with this for 50 years."
Kellogg said it was not an easy out for the court to just say the pipeline would pass under the trail. Federal law, he read, concerns "rights-of-ways upon, over, under, across, or along any components of the Appalachian Trail."
And he resisted Roberts' view that the trail would become a barrier that could not be breached.
Pipelines already pass under the trail, and new ones can be built on the private and state lands over which the trail traverse, just not federal land, Kellogg said.
"Insofar as it is on federal land, where the most beautiful parts of the Appalachian Trail are to be found, through the national forest . . . through the park system, Congress drew a bright line," he said.
Even if the Supreme Court agrees with the pipeline builders, significant obstacles to the project remain.
Earlier this year, the 4th Circuit threw out a state permit for a pumping station in a historic African American community in Buckingham County, Virginia, saying the builders failed to consider whether the facility would unduly harm a minority group.
And the lower-court ruling on the Appalachian Trail crossing had three other elements that are not part of the appeal to the high court. Those judges also said the permit didn't comply with mandatory standards for protecting soil, water and wildlife; that the agency didn't take a hard enough look at landslide and erosion risk; and that the Forest Service rejected alternate routes without fully analyzing them.
The consolidated cases at the Supreme Court are U.S. Forest Service v. Cowpasture River Preservation Assn. and Atlantic Coast Pipeline LLC v. Cowpasture River Preservation Assn.
Sign up for the daily JWR update. It's free. Just click here.