The U.S. Supreme Court has agreed to hear Atlantic Coast Pipeline LLC’s (ACP) appeal of a pivotal appeals court ruling that has jeopardized the natural gas pipeline sponsors’ plans to cross the Appalachian National Scenic Trail.

The nation’s highest court on Friday granted writs of certiorari to both ACP and the U.S. Forest Service (USFS), agreeing to hear oral arguments regarding their challenges to a December ruling by the U.S. Court of Appeals for the Fourth Circuit. The circuit court decision tossed a critical USFS sign-off for the 1.5 Bcf/d, 600-mile ACP, including a right-of-way (ROW) to cross underneath the Appalachian Trail as part of its path through the George Washington National Forest.

The Supreme Court case centers on the Fourth Circuit’s conclusion that the Appalachian Trail is part of the National Parks System and thus the USFS lacks authority to issue the ROW. In its petition to the high court, ACP counsel argued that the appeals court decision would effectively make the trail a barrier for new infrastructure projects in the region.

Project opponents, meanwhile, have argued that there is no precedent establishing USFS authority to approve a pipeline ROW to cross the Appalachian Trail. Most pipelines crossing the trail on federal land existed before the trail was created, they have said.

ACP spokesperson Aaron Ruby said the Supreme Court’s decision to grant certiorari was a “very encouraging sign” for the project, which has faced relentless legal opposition in its efforts to provide a conduit for Marcellus and Utica shale gas to cross through mountainous terrain from West Virginia into Virginia and North Carolina.

Assuming a “favorable resolution” of ACP’s case by next June, the project could begin full construction next summer, putting it on track for completion by late 2021, Ruby said.

“The law and the facts are on our side, and we’re supported by a broad coalition of stakeholders,” he said. “The U.S. Solicitor General, 16 state attorneys general and more than a dozen industry and labor organizations all agree that the U.S. Forest Service has the authority to approve our Appalachian Trail crossing.

“More than 50 other pipelines cross underneath the Appalachian Trail without disturbing its public use,” he added. “The public interest requires a clear process for the issuance and renewal of permits for such pipelines, and other essential infrastructure.

“The Atlantic Coast Pipeline should be no different. In fact, the pipeline will be installed more than 600 feet below the surface and more than a half-mile from each side of the Trail to avoid any impacts.”

Analysts at ClearView Energy Partners LLC expect the Supreme Court to hear oral arguments early next year.

“If the Forest Service and ACP’s appeals fail on the merits, we would characterize the broader industry implications as a new but not insurmountable constraint,” analysts said in a note to clients. “Project sponsors would be on notice that greenfield crossings of the Trail are more problematic than previously assumed.”

ACP is a joint venture of Dominion Energy Transmission Inc., Duke Energy Corp., Piedmont Natural Gas and Southern Company Gas.