Given its potential to set a major precedent for future infrastructure development across the Appalachian National Scenic Trail, private and public entities are ratcheting up the debate over the Atlantic Coast Pipeline LLC’s (ACP) U.S. Supreme Court case.

A number of entities filed amicus briefs with the nation’s highest court over the past week, most to express support for the embattled 1.5 Bcf/d, 600-mile natural gas pipeline. ACP has faced a series of regulatory and legal setbacks since securing a certificate of public convenience and necessity from FERC in a split vote in 2017.

ACP and the U.S. Forest Service (USFS) are petitioning the Supreme Court to overturn a December 2018 decision handed down by the U.S. Court of Appeals for the Fourth Circuit. Issuing an opinion critical of how the USFS handled its review of the project, the Fourth Circuit tossed the agency’s approval of the pipeline’s plans to cross two national forests along the West Virginia/Virginia border.

The Supreme Court challenge centers on whether the USFS can authorize crossings of the Appalachian Trail, which was designated under the National Trails System Act to be “administered primarily” by the Secretary of the Interior.

Counsel for Mountain Valley Pipeline LLC (MVP), a similarly routed greenfield pipeline that also proposes crossing the Appalachian Trail, said the Fourth Circuit’s decision is flawed and contradicts congressional intent.

The decision is “impossible to reconcile with the congressional objectives animating the pipeline right-of-way provisions of the Mineral Leasing Act, which Congress added to the law during the oil embargo and the energy crisis of the early 1970s specifically to facilitate issuance of pipeline rights-of-way on Forest Service and other federal lands.”

Construction is roughly 90% complete on MVP, with more than 264 miles of pipe welded and in place. The Fourth Circuit’s decision has forced MVP to halt construction of its Appalachian Trail crossing, stalling progress on the “almost-completed” pipeline.

“Every alternative route potentially available to Mountain Valley also crosses the Trail,” MVP’s counsel wrote. “Thus, as a direct result of the Fourth Circuit’s decision, energy consumers have been cut off from a major new source of domestic natural gas and any future prospect of new pipeline infrastructure to serve the Eastern Seaboard has been cast in doubt.”

Representing the state where both ACP and MVP would originate, West Virginia Attorney General Patrick Morrisey expressed “deep concerns” with the Fourth Circuit’s decision. Joined by 17 other states, Morrisey wrote that the provisions of the Mineral Leasing Act should balance “robust energy development and responsible management of public lands.

“States are invested on both sides of this scale,” he wrote. “Many states’ economies depend on exporting oil and natural gas reserves to surrounding states, and the country’s overall economy is built on the bedrock of a resilient and well-supplied electrical grid.”

The Fourth Circuit decision “destroyed the balance Congress baked into the Mineral Leasing Act and cut off thousands of miles of federal land from development. These concerns are especially pressing because the decision does not simply question the Forest Service’s judgment or ask for a redo: It makes it impossible for any federal agency to grant any easement crossing the Appalachian Trail.”

At the federal level, a coalition of Rep. Jeff Duncan (R-SC) and 61 other members of the U.S. House of Representatives also chimed in to support ACP and energy development more broadly.

“Whether through greater economic strength, increased national security, or simply a lower power bill, the American people benefit from the cheaper and cleaner-generated electricity that results from pipelines like the one at issue in this case,” the lawmakers’ brief said. “…Congress has long supported domestic energy production, including natural gas. This support flows from multiple considerations, ranging from national security to economic development to environmental protection.”

Trade groups including the National Manufacturer’s Association (NMA) and the American Forest Resource Council (AFRC) also stepped forward to defend the authority of the USFS to approve the proposed trail crossing.

“With much of the National Forest landscape in poor health, active management is badly needed throughout the country to reduce the risk of catastrophic wildfire as well as insect and disease outbreaks,” the AFRC’s counsel wrote. Forestry associations “have a strong interest in maintaining the ability of the Forest Service to conduct active management without judicial imposition of undue constraints. The effect of the decision…is not limited to pipelines.”

The Fourth Circuit’s ruling “abruptly changes the management regime that has been applied to trails and adjacent lands under the complex process of forest planning.”

The NMA, representing a “broad array” of manufacturers and other businesses, highlighted the importance of the “reliable supply of natural gas, oil and refined petroleum products provided by U.S. pipelines to the economy.”

In addition to industry, ACP can also count labor among its supporters, or at least the members of the numerous labor unions that joined in filing a brief urging the court to overturn the Fourth Circuit’s “erroneous interpretation” of the Mineral Leasing Act.

The unions in support included the United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry of the United States and Canada, AFL-CIO; the International Union of Operating Engineers; the Laborers’ International Union of North America; the International Brotherhood of Teamsters; and the Pipe Line Contractors Association. They warned of “harmful consequences” for “many thousands of American workers, state and local communities, and U.S. energy infrastructure, in the short and long term.”

Meanwhile, the Appalachian Trail Conservancy filed a brief urging the Supreme Court to take the time to understand the “complex network of land agencies and trail clubs administering local segments of trail.” To sufficiently weigh the implications of its decision in the ACP case, “the court will need to step beyond mere labels to understand in more detail how the trail is managed.”

As the “primary private-sector steward of the trail,” the conservancy said it wants to ensure “the continued vitality and effectiveness” of the system in place to manage and preserve the Appalachian Trail.

“The Conservancy hopes the court will make clear, whatever its decision, that pipelines and other infrastructure must respect and preserve the trail in full,” the group wrote.