A new federal appeals court ruling could raise questions over the legal viability of the narrowed downstream greenhouse gas (GHG) emissions analysis for natural gas pipeline reviews adopted by FERC under the Trump administration.

In a case challenging a December 2019 certificate order for a 72,400 Dth/d upgrade project on the Tennessee Gas Pipeline (TGP) system, the U.S. Court of Appeals for the District of Columbia Circuit remanded — but did not vacate — the Commission’s decision in a ruling late last week. The court cited flaws in the agency’s GHG analysis for the project, which involved 2.1 miles of new pipeline and a new compressor station in Agawam, MA.

In sending the certificate order back to the Federal Energy Regulatory Commission for further review, the court...